Journey Through The Solar System
Anybody gazing upwards into the night sky is looking at a place where human knowledge outstretches our ability to explore by magnitudes so great they are almost impossible to contemplate. In the vast scope of our collective knowledge we know that the far edges of our universe are so remote that the light burning in stars there light takes billions of years to reach us. We know that all of the distant twinkling lights in our night sky are other stars like our own Sun, with their own solar systems. We know that all the matter that forms our world and even our own bodies was forged in the heat of exploding stars. We know about black holes, that stars are formed in nebulae, that the universe we see is expanding, and that there is far more to the universe than what we see. We even understand that, given the right circumstances, we could go beyond everything we know into parallel dimensions in places that obey different laws of physics. Yet, for all our learning and understanding the best we have managed for ourselves are a few short excursions around our own Moon. Why is this so? Why can any person look out into the universe and know so much about it, but yet be so powerless to get any closer? Why do we mostly remain stuck on Earth, so many years after the first human explorer was shot into space. Why aren't we going and seeing our neighbouring planets and moons? What - all of us brought up on stories of space exploration, real and fictional, might ask - is the hold up?
Looking back from our first and only voyage to another world - the seven landings by the United States on the moon - it is perhaps easy to be disappointed that nobody has been back in the decades since. But our great breakthroughs in science and technology has shown us the other side of things too; the vast distances between the planets and moons, and the huge amount of nothing in between. The solar system being, in reality, a scattering of distant pinpricks of rock and gas, spread out over such huge distances that it took us, watching from our planet, centuries to work out how it all fit together. Our fictional depictions tend towards the more fanciful - spaceships firing laser guns at each other in dense asteroid belts - because the reality is a bit more prosaic. Mostly it comes down to maths, and firing rockets out of high-tech tin cans in precise bursts to slingshot around planets when we eventually get there. The distance is the most impressive and dispiriting thing about space flight and exploration. A jaunt to the moon takes several days, and beyond that is months and months of uneventful slog to reach the nearest planets, Mars in one direction, and Venus in the other.
So it seems like our theoretical journey through the solar system might not be all it's cracked up to be. Days and days of floating through a huge amount of nothing much, heading for cold, seemingly lifeless lumps of rock. It does not seem like much of a story to tell. In fact, however, there is much to see in our neighbourhood of space, and much to learn about how we came to understand where we are in the universe, and how we have explored outside of our planet, and where we can go from here. Let us take a journey through space and time; out into the solar system, and back and forward through history and the future.
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Where We Are
At a glance the great glittering fabric of the night sky seems unchanging and steady, but looked at for longer it moves, rotating around our view down on the ground, and it moves in a predictable way. Way back in the time of ancient civilisations this routine was noticed and recorded, and the five stars in the sky that seemed to defy the regular pattern were of particular interest. These days were call them planets, and we know that they, like us are orbiting around the sun. In past centuries these "wandering stars" were the cause of much superstition; the strange sights in the sky led to the mystical art of Astrology being practiced in royal courts, where the rulers would listen to the predictions of what the movements of the stars would foretell. The world ran to the seasons, everybody's lives depended on the weather, the crops, the growing and sowing seasons. The stars were the ever-present backdrop so it was only natural for everybody to place huge importance on their comings and goings, to consider them a divine presence, even to draw constellations between them and imagine that they symbolised things on Earth. If it came naturally for humans to assume that stars and planets were the manifestation of the gods, then so to it was natural to think that the Earth was at the centre of it all. Everything seemed to be going around us after all, and the Earth was clearly too massive to move anywhere.
Nicolaus Copernicus was born in Poland in 1473. After his school years he studied in Italy and became a church canon back home in Poland, a position where he could practice astronomy as part of his day to day work. He grew prominent enough in the field for even the pope to take notice. At the time astrology and astronomy were almost one and the same field. Many astronomical studies were In service of astrological forecasts. While in Bologna Copernicus had roomed with the head astrologer for the city, the man who prognosticated for the entire population, but of course was especially valuable for informing the ruling princes and dukes about their military strategies. Even in this credulous age there was scepticism about the supposed powers of the heavenly bodies and Copernicus was exposed to these ideas.
He was hardly the first to develop a theory of 'heliocentrism' - placing the sun in the centre of the solar system rather than the Earth; some Ancient Greek astronomers had postulated such an idea, as did Islamic scholars of the middle ages, though non had the powerful telescopes required to confirm their ideas, and they all fought against orthodoxy. for the Greeks it was Aristotle and his Earth-centric model of the universe. Since the ancients concluded to their satisfaction that the Earth was a sphere they expanded from there to assume that the heavens above them must be hanging on a.series of great lightweight "crystal spheres" enclosing the Earth at the centre. Ironically Aristotle's achievements in philosophy and politics and his belief in questioning and observation made him so revered among the learned educated classes that they took his faulty.model of the universe as correct for centuries. Aristotle's universe also informed how the Catholic church saw of the universe and as the church was the most powerful body in the medieval world it is understandable that Copernicus kept his theories to himself for much of his life for fear of incurring religious wrath. The assumption that the Earth sits at the middle of everything shows how much people will bend observations to an idea rather than vice versa. Another great ancient thinker - Ptolemy - expanded on Aristotle and came up with complicated Earth centred model to account for strange retrograde movements of planets in sky. The "wandering stars" rotated around their own little orbits as they travelled around the Earth. This would explain the curious swerving movement of the five planets in the sky - how they would travel one way, then weave back on themselves - while keeping the Earth in the middle. Only with the advent of the renaissance did more accurate ideas begin to come to the fore. Astrology began to look increasingly wonky as more and more moons and planets were sighted in the skies, but Copernicus pre-dated much of this. In his time nobody could agree on whether Venus or Mercury were nearer to the Earth.
Mercury, known now of course to be the closest planet to sun, is often overlooked in stories of the solar system. Where Venus shone like a jewel in the sky, inciting thoughts of Venusian civilisations, Mercury hid low on the horizon, only visible early in the morning and late in the evening, and all.but impossible to watch through a telescope thanks to its proximity to the sun. It is the smallest planet, barely larger than our moon and looking very similar, but it has been known since ancient times, hence it name; Mercury is the Ancient Roman God of commerce, travel and communication, and the planet, orbiting well inside the Earth moves very rapidly across the sky like it's namesake could in mythology. The year on Mercury is.only 87 earth days (so a.30 year old on Earth would be 124 in Mercurian years). Not that any humans would be wont to live there of course. Clearly the temperature so close to the sun is high; 400 c, during the day, plunging to minus 180 in the night. Some of the craters of Mercury surprisingly have shown signs of ice in their darkest recesses. Radiation is another factor that makes surviving on Mercury a challenge. Seven times as many irradiating particles hit the surface compared to the Earth, though it might not be beyond the realms of possibility. Mercury has a magnetosphere, unlike the moon, and this deflects much of the solar wind.
Landing during night and burrowing under the surface would be the best way to land people on Mercury, should we ever want to. It is slightly further than mars, but the gravity of the sun would assist somewhat in getting close. Too much in fact, as any missions, like the Mariner 10 and Messenger probes, have to take into account the strong pull from the sun and the planets highly eccentric orbit that's a third longer than it is wide. To stop it crashing into the sun and to save on needing large fuel tanks for manoeuvring rockets mission controllers sent Messenger on a complicated path around Venus and Mercury to get it into a stable orbit. Mariner 10 and Messenger are the only two missions launched to Mercury to date and have provided nearly all the close up data of the planet, as they can look without the unwanted hindrance of the sun in the background. Messenger now sits in a scattered pile of debris on the surface, the first and only human built object on the surface, it mapped all of the surface over four years, revealing along the way the ice in polar craters, what could be fault lines from tectonic movements and ancient volcanoes. The craft also took a panorama picture of the rest of the visible inner solar system as it appears from Mercury, echoing the same pictures taken by he Voyager 1 mission looking back at the Earth from Saturn. Mariner 10 eventually ran down it's power source and is probably still out there orbiting the sun though we have never caught sight of it.
Copernicus would no doubt be thrilled to have such conclusive proof of his theory though he would probably have plenty of questions about what he was looking at (How did I end up in the 21st century? not being the least of them) . To people who had not yet been introduced to Newtons theory of gravitation the sight of all the planets somehow floating around in space would have been hard to understand. Copernicus model with the sun in the middle and mercury nearest fitted observations well, the problem was he had no idea how his universe could possibly move, since the Earth patently was not attached to the surface of one of the giant celestial spheres. Nobody for example had ever run their sailing ship into a solid wall in middle of the ocean holding the Earth round the sun.
Copernicus published his masterwork one year before his death aged 70 in 1543. The theory laid largely on the margins for many years, not helped by being held to be heretical by the church, as the world gradually caught up and confirmed it's basic ideas. Though Copernicus is remembered in history as the man who overturned thousands of years of error, and placed us correctly in the solar system, it was another man - Johannes Kepler - who defined it properly, and in consequence set the ball rolling (almost literally) on the whole modern world of physics. Kepler, born in what is now South West Germany in 1571 was raised a Christian in a time of great Protestant reform in Europe. He was sent to seminary, and thanks to his upbringing he was obsessed with God, but unlike most of his peers his was not a mind given to unquestioning obedience to dogma. He was inspired to understand how God had created the world, and reasoned that if God was everywhere, as he had been taught, then the unerring certainty of geometry and mathematics were surely divine, and could apply to everything in the world not just the movement of the night skies. It was a question he took with him to university, where the theory of Copernicus was taught. After his graduation Kepler became a maths teacher, and spent much of his spare time trying to make geometry fit into the Sun-centred solar system. He imagined that the five planets other than the Earth were supported by the five solid shapes, held up by invisible supports. It was a nice idea - a grand theory of everything - but completely wrong. Fortunately for Kepler's place in history there now followed a large Catholic uprising in Graz, where he was working, and as a prominent protestant he moved away.
Kepler made his way to the court of a Danish nobleman called Tycho Brahe in Prague. Brahe was one of history's great nearly men - he had made the most comprehensive observations of the night sky of his time, but still stuck to an Earth-centred universe. He created his own Earth-centric system the nearly fitted his data, but then dropped down dead shortly after meeting Kepler - the man who would take his observations and come up with the correct answer. For Kepler, convinced of the Copernican system, Brahe's close-but-not-quite system was not good enough. He had struggled to fit in among the court of the nobleman, who was just as fond of lavish parties and banquets as he was of scientific inquiry - leading to his demise from, of all things, a ruptured bladder after a night of over indulgence.
With the death of Brahe, Kepler was now free to study the data an confirm that the Sun was the centre of the universe, with the planets orbiting in perfect circles. The problem was that when he did try and work everything out, he had to conclude that the planets must be orbiting the sun in an oval ellipse, speeding up slightly as they passed close to the sun, before slowing slightly as they arced out the edge of their orbits. It was only a small difference, a matter of eight minutes out from what he was expecting to see if the planets traced a perfect circle around the sun, but it was enough, and for all that it rocked his lifelong worldview that God was perfect and geometry was the basis of everything he stuck with his conclusion. In doing so he set the precedent for all modern science - theory was fine, but it had to be backed up with observation. The planets were evidently falling around the sun, and with Kepler's laws of motion their movements could be predicted perfectly. In time, we would come to find that the sun itself is falling around the centre of the galaxy, one of billions of similar stars doing likewise, dragging their own solar systems around with them.
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Getting There
Our default method of getting into orbit is the liquid fuel rocket - a 1920s invention that laid largely dormant for two decades. Modern rockets owe a great deal to the Second World War - the Nazis pumped money into the V2 rocket aimed at flying over the channel and dropping it's warhead on the citizens of London. After the end of hostilities the Russians and Americans pounced on the Nazi rocket technology, using it's men and resources as the basis for their own experiments. In the 1950s it seemed as likely that pilots would fly into space in a rocket powered plane as strapped in a capsule on top of a missile. But while test pilots of the era shot across the deserts of California and Nevada they could not match the sheer power of the ever larger rocket engines being launched straight up from a launch pad. The fastest planes could touch Mach 3 - three times the speed of sound - rockets could manage that a minute after blast off.
The space race of the 1950s and 60s was just as much a military posing match as a journey of scientific discovery. When the Soviet Union launched the first satellite, Sputnik, in 1957, the great achievement caused shockwaves of alarm in the United States. The country that had become used to being militarily dominant since the 1920s had to face a sworn enemy with better rocket technology than them and the ability to build nuclear weapons. The rocket that launched the Russian space probes and cosmonauts was really a military ICBM - or Inter Continental Ballistic Missile - and sticking a few men in shiny suits atop the nose cone in a space capsule was a convenient propaganda exercise for the rival government's to one up each other while getting huge piles of funding for their nuclear weapons delivery platforms.
The irony is that while the 1960s was a time of great triumphs in space those successes came at the expense of the more fantastical visions of the future. The idea that seemed imminent at the dawn of the decade - of great space planes soaring into orbit - rather fell into the wayside in the 1960s as the Ballistic Missile made even the most rapid supersonic aircraft redundant for many military uses. The Apollo moon landing missions almost became a victim of their own successes so thoroughly did they achieve their goals. Marry the technology that got the astronauts to the moon with the emerging computer technology and the real reason that people haven't been to the moon since 1972 becomes clear - robots have taken over from people because they can everything, save give their emotional reaction to what they see, for a fraction of the cost. Thanks to our close-up encounters with the moon we are used to seeing bleak, colourless worlds in our solar system but not all are like that.
The 20th century saw a great leap bringing everything into focus; the colours, the dramatic geography, the potential for life. Emblematic of this bigger picture is what the Cassini spacecraft saw when it flew by Saturn's moon Enceladus in 2005 - a small place, tiny compared to some of the other moons of Saturn, the little moon was only really familiar to astronomers until the first close up encounters turned it from a bright point of light in telescopes and into a space superstar. What Cassini's cameras saw from the moon were strange fissures and cracks in the jewelled white surface, along with huge eruptions coming from the surface. Further investigations showed that the tiny moon was spewing water into space from geysers. Just like on Earth these were huge jets of water erupting from the surface, but far, far greater than any geyser on Earth. The stripes across the crust were detected to be a warmer temperature, suggesting the heated water inside burst through and formed the fissures.
Enceladus was one of many objects in the night sky not visible to the naked eye but visible through telescopes, and now it had been seen close up for the first time after centuries of distant observation. Just one small dream fulfilled, but one of many that provide the picture of our neighbouring worlds - the other moons of Jupiter and Saturn, the outer planets Uranus and Neptune, the dwarf planet Pluto, the asteroids, and the comets. The recurrence of the comets shooting across the night sky that told a mysterious tale we would have to decipher; the decoding of the movements of the planets, moon and comets would begin the long journey to travelling to them ourselves.
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The Moon
The only other world we have visited, our Moon moon's surface seems familiar to us now, in the decades after the first landings there. We know it as a cold, airless place, grey and dusty, cratered and scattered with rocks. Things are a little more complicated than that; for one the cold only lasts while the sun is around the other side - in the lunar daytime the temperatures reach 100 degrees Celsius - 270 degrees higher than they are at night. With no atmosphere the moon heats and cools very quickly, and the lack of atmosphere has a few other strange side effects. The complete absence of any colouring or haze in the air makes a mockery of our evolved perceptions of distance- what to the eye look like small rocks close by can in reality be huge boulders far away.
The conspiracy minded back on Earth have latched onto some of the seeming anomalies as ways of casting doubt on the authenticity of the moon landings, but in reality the truth is often counter intuitive when alien worlds are concerned. A frequent question from the suspicious is 'Where is the glittering sky of stars?' In the photographs from the moon the sky is strangely blank - implausible surely? In fact on the lunar daytime the surface reflects back so much bright light as to block out most of the stars (and anyway the cameras they had would need to be set to very long exposures to capture starlight- stars are very very far away after). Flying around the Moon was another matter - when the CSM went into the moons shadow the lone pilots reported seeing what looked like a sea of white, a field of billions of stars impossible to see from Earth or the moons surface with the interference of sunlight.
The lack of a blast crater under the lunar landers causes raised eyebrows and disbelief, but a rocket blast crater only forms on with the flow of air currents. Without atmosphere the dust dissipates more widely with less pressure. The same phenomenon caused the astronauts white spacesuits to become caked with grey lunar dust. Unlike on Earth the moons dust is jagged and sharp because there is no air or water to smooth it out, and without air currents all the dust the astronauts kicked up simply stuck to them. Not just unsightly, the thousands of sharp flecks threatened to clog up equipment and cause short circuits in the electrics of the cramped lunar lander. And any major problem with the lunar module ascent stage would have left the two moon walkers stranded on the surface facing certain doom. Any future planetary landers are likely to follow the lead of the space shuttle and ISS have some space for suiting up. Dust may be a prosaic problem but it's a major headache for any space mission. We get used to dust falling to the ground and being swept up on Earth; in low gravity it floats around forever, never settling.
Perhaps it's part of human nature to have a tiny bit of disbelief when it comes to the moon landings. It still seems fantastical that teams of people could have made it so far from home, in such small simple craft, and returned back safely, and done so nine times (including the ill fated Apollo 13, and the Apollo 8 flyby) in the space of a mere five years. There were two factors made the landings a great success. One was money. Apollo cost around $25 billion, in the 1960s. Factored for inflation that makes about 160 billion today. Money can make a lot of dreams come true, but Apollo did very well considering that even that mammoth figure was but a fifth of the US expenditure during the Vietnam war over a similar duration, and one twentieth of the ongoing cost of the Iraq-Afghanistan wars of the 21st century. This shows the value of the other great asset, the great level of expertise assembled and the way it was organised. So rigorous was the astronaut selection programme that some of the crew members had qualifications in astrophysics, never mind the braintrust on the ground. The traditional image of astronauts paints them as daredevil "flyboys", risk takers, with very large cajones. As indeed they had to be to both know their way around the cockpit of a spacecraft heavily derived from aeroplane technology and be willing to face an estimated 50/50 chance of not coming back - as the estimate had the chance of a successful landing and return before the Apollo 11 launch. But they were smart too, they had to be to work the complicated computer systems that controlled the engines, the fuel system, the navigation, the docking, the landing. Then they had to know exactly what to do during the most remote, scrutinised, important and expensive hours of human activity ever known as they explored the moon's surface. Landing was not merely a publicity stunt and hundreds experiments and activities were scheduled and performed to a strict routine.
During the first moon walk, Neil Armstrong and Buzz Aldrin spent two and a half hours walking on the surface. The number of hours spent on the moon gradually climbed up and up with each mission. Apollo 12 had two moon walks of nearly four hours each, and at the furthest travelled nearly 200 metres from the Lunar Lander. Apollo 12 pioneered the Apollo Lunar Surface Experiments Package (ALSEP), a collection of instruments for measuring (almost) everything under the Sun, including seismic, radiation and magnetic detectors. The radioactive isotope powerpacks meant that the ALSEP could keep running for most of the 1970s before being shut down. Moon rocks aside, the most long lasting of the lunar experiments were (and are) the lunar reflecting beacons, specially shaped panels deployed by the landers that Earth telescopes can fire lasers off of to measure the exact distance to the Moon. They are still there, and still able to reflect back a signal. The crews of Apollo's 15, 16 and 17 had the benefit of the extraordinary lunar rover. By far the most expensive, and slowest car ever built, the Lunar Roving Vehicle (LRV) could tear along at 11 mph, making it the holder of the off-world Land Speed Record.
The Moon rover was not just to show off - it allowed its driver and passenger to safely venture much further from the lander than by walking alone. This included exploring craters and hills that would have been otherwise out of bounds with the oxygen supply available in the lunar space suit - though the astronauts were never placed in a location that would have been too far to walk back to safety from. The great expense came partly from the huge amount of testing needed to ensure the LRV would not leave it's occupants stranded, but also from the need to fold up and fit in the Lunar lander without being too heavy. The light weight was also essential because the vehicle was designed to carry back a cargo of moon rocks as well as two people. (All the missions brought back 382 kg of moon rocks - about the weight of five and a half extra people). The rocks were far more useful to geologists than being mere curiosities; laying undisturbed and unmoulded by winds and rain, moon rocks are billions of years old and can give great insights into where the Earth and moon might have come from. Apollo 17 discovered ancient volcanic soil, and had the only fully qualified scientist to ever tread on another world, Harrison Schmidt, on board to direct commander Gene Cernan, himself the last man to leave the moon at the end of the mission, where to dig.
Uniquely for any car, the Rover also needed to work in much lower gravity and cope with the jagged un-eroded moon dust - hence the use of thin wire mesh tyres rather than rubber. The perfect parabolic arcs of dust slowly kicked up by these wheels provides another telltale clue that the film from the moon is genuine. To replicate the effect the Rover would have first needed to be driven around inside a vacuum, and then the "dust" would need to be a material that could float as if in a lower gravity environment - by which stage the Occam's Razor logical maxim asks if pretending to convincingly go to the moon (eight times) would in fact be harder than just really going there. Like the rest of the equipment on the lander's lower stage the LRV was left on the moon's surface as the crew came back home in the ascent section. In the 2010s a NASA craft called the Lunar Reconnaissance Orbiter mapped the whole of the surface in unprecedented definition, in doing so it captured all six Apollo landing sites, even showing the trails left by the astronauts and the Rovers radiating out from the only evidence of human activity anywhere but the Earth.
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Venus
When we imagine the solar system most of us probably picture the diagram of a thousand school textbooks of all the planets lined up shoulder-to-shoulder orbiting the sun. The night sky above our heads shows the reality; The small dots of light, almost imperceptible against all the stars are the planets. Only one planet really stands out prominently in the sky. After the Sun, Moon, and the International Space Station, Venus is the brightest object, and is easily seen on any clear night. Unsurprisingly Venus is the usual suspect when unidentified bright lights are reported in the sky by people hopeful of seeing a UFO. Mars is a little tougher to see, because it is smaller and much dimmer, but visible through any small birdwatchers telescope clearly enough.
While the American astronauts and Soviet cosmonauts publicly waged the cold war in their space capsules a rather less showy contest was being held between the two nations space probes as the were fired to the planet's of the inner solar system. Managing to intercept another world and then land an object on it is not an easy task. All the planets are constantly in motion around the sun, their moons are in motion around those planets, and all are moving at different speeds, some with more erratic and distorted orbits than others. Then there's effect that the gravitational pull of planets have on a trajectory - get closer in and the spacecraft will be pulled closer and closer until it smashes into the ground. So simply shooting something in the direction of Venus will not work, as Venus is a moving target sitting in an invisible gravity field, and the launchpad is also moving. A successful landing is as much a case of getting the world to land on the probe as landing on the world. Automation and basic computer programming made all the difference to space missions, as they could be coded with instructions to account for all the adjustments needed for a journey, manned or unmanned. First to make a flyby of another planet was Nasa's Mariner 2 in November 1962. Mariner 1 has blown up on the launch pad, but number 2 made it to Venus and successfully scanned the second planet, recording very high temperatures, confirming the bright starry glow shining across space was not the result of oceans or alien civilisations, as had once been imagined by many people, but the sun reflecting off thick opaque clouds that blotted out all trace of the surface.
The Soviets had won the race to the Moon in 1959 with the Luna crafts, and they landed on Venus in 1970, the Venera probe the first piece of human hardware to land on another planet. This was Venera 7, and the high number of the mission showed what a struggle it had been for the persistent Soviet space bureau to make a successful landing. The van sized machine was not equipped to send back photographs but it could radio back the extraordinary temperature and pressure readings, giving us the confirmation that it is going to be a long time before we might ever have the technology to walk on Venus. Venera 7 lasted all of an hour before it melted and buckled too much to send back any more data. Five years later Venera 9 sent back the first photograph of the surface of another planet. The fuzzy black and white panorama showed a bleak environment covered in large rocks around the rim of the bell-shaped landers base. The craft also took measurements of the cloud layers and the amounts of acid and other chemicals in the seething boiling air it parachuted through. The mission also proved the efficacy of building separate Orbiter and lander parts of a spacecraft, where the lander could be dropped on a one way mission to the hostile ground while the orbiter keeps flying around above, relaying signals from the lander back to earth as well as gathering its own data. In 1982 the Venera missions reached their zenith with Venera 13. This missions lander withheld the Venusian weather for two hours, scooped up some of the surface and took twenty two photographs, fourteen of them in colour- the only such images of the surface of Venus to date. The soil analysis suggested this area of Venus had a surface similar in make-up to the rocks made from fallen and compressed ash falls found in volcanic areas on Earth.
Not only were the large Russian probes sqaushed, melted and dissolved on the surface of the most hellish place in the solar system, but they endured some frustrating ill fortune. The first Venera equipped with a colour camera (Venera 11) could not take any photographs because the lens cap melted on during the descent. The same problem had affected the previous two landers - their panorama photographs were meant to be 360 degrees, but each time one of the two cameras lens caps did not come off. A later mission intended to sample some of the Venusian soil. The sampler was on the end of swing arm that would be released from the side of the craft and fall down to the surface. The sampler was successfully released but did not send back data.The problem was trivial but terminal, and annoyingly familiar; this time the camera lens cap had come off properly, only to fall directly under the sampling arm, and there was no way to nudge it out of the way. Sensitive to the demands of the Soviet propaganda machine the data from these missions was kept secret for many years, so although the Venera probes confirmed the crushing pressure and extreme temperatures that would make human exploration almost impossible, and took photos from a place hotter than the inside of an oven they did not get much global recognition until long afterwards.
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Mars
The Venera missions are the only landings of hardware on the surface of Venus but a great deal has been learned from flying in orbit around Venus and scanning it from a distance. The Mariner crafts used radar detection to scan the surface, as did the 1989 mission by the Magellan probe, providing a clear map of mountains, fault lines, and possible volcanoes. What is certain is that Venus in it's current state is not habitable, and a manned mission seems ridiculous when even robots are melted and crushed. Venus has no moons to explore, so for all it's mysteries it has become a place we observe rather than explore. Mars has become the focus of our explorations and future dreams of long-range missions. The Soviet Mars 3 craft was the first to land successfully on the red planet in 1971, while six years earlier Nasa's Mariner 4 took the close-up pictures of Mars, the first close up picture of another planet from space. In 1976 Nasa sent the most sophisticated probes to date, the Viking twins, 1 and 2, into the time capsule of the Martian landscape to take colour photos of volcanic rocks and take measurements of the conditions. Viking was static on it's spidery legs, it's only moving part a surface scoop, while the Soviet Union sent the less advanced but much more mobile Lunakhod rovers during the 1970s. Following suit Nasa has sent the remote rovers Sojourner in 1997, the Spirit and Opportunity twins on opposite sides of Mars in 2004, and the much larger Curiosity rover 2012.
For all it's flame red appearance, Mars is a very chilly place. At the equator, with the sun high in the midday sky it's not too dissimilar to parts of Earth reaching the twenties Celsius. At night though the reading plummets down to minus fifty. At the poles things are even more frigid - minus 240, hence the ice caps that are visible to orbiting spacecraft. Mars has a very thin atmosphere, only 1 percent the density of Earth, so the kind of wild dust storm that toppled the landing craft at the beginning of the movie The Martian could not happen in reality. Without an atmosphere the surface is heated entirely by the presence of the sun. The technology to keep people alive in such fluctuations has been an integral part of spaceflight since the very beginning. The Apollo moon walkers suits had to contend with similar variations in the lunar day and night, and the International Space station swoops between day and night constantly on its orbit with the crew inside in their normal clothes. If the ISS life support fails though, the crew can always evacuate back to the safety of Earth rather than freeze. On Mars a failure of any habitation module in a base at the very least would lead to the end of any mission and a long flight back home. At worst there would be no crew to bring home.
The thin atmosphere makes landing heavy spaceships delivering equipment and astronauts a risky business. Twenty or so cars worth of bits and pieces would be needed to be bundled in landing craft to establish a rudimentary base on Mars, and without reliable rockets to slow the descent the impact would create an impressive, if expensive, man made crater. Unlike the moon, where there is no.atmosphere, there are enough particles in the Martian atmosphere to stop us from using a thin spindly spider-like lander with paper thin walls like we did on the Apollo missions. We'd need something larger and more solid, and that drives us the launch weight and the launch expense greatly. The latest robot explorer from Earth, the car sized Curiosity rover, landed successfully on the planet using the so called Sky Crane descent. Despite the unusual name it bears similarities to the familiar way of doing things only the 'crane' is a square platform with big retro rockets at the corners and the payload hanging beneath like the basket of a hot air balloon, saving the complication of building rockets into the rover itself. With a much thinner atmosphere to fall through than Earth the mars lander must sit inside a wide flying saucer-looking heat shield to get enough drag to slow down, and big parachutes will need to be packed into the ship to be deployed. For safety there would probably need to be a backup set in there too.
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Reality Check
The big stumbling block to making travel to Mars a reality is the thing separating a quick week holiday to the Moon and a two year round trip - self sustainability. Without constant supplies from Earth the future Mars Cruiser and Base needs to generate it's own power, grow its own food, and recycle it's own water. In theory we would seem to be well on the way to solving these conundrums. The same drive to reduce the impact of modern life on Earths resources has applications in space. Currently astronauts drink water that has already been though their systems several times, it is purified by filtration systems similar to an water treatment plant on Earth.
There are some complications standing in the way, however. Some are fairly obvious - with far less solar energy we would power things with radioactive isotopes, not the most safe things to have around, Martian explorers would stow them securely on ship and deploy them far from their base. Others are more pervasive. We imagine that we could build a big sealed greenhouse, water it with some of the traces of water we know from robot explorers that we will find in the Martian soil, use the CO2 in our exhalations and our waste products to make fertiliser and grow dinner. This might not sustain more than a tiny crew though before more advanced methods would need to be used. After all, more waste and co2 would need more crew and more crew would need more food. And while we could use the plants to absorb our c02 they would repay us with oxygen. Excellent for keeping us alive, but only in the.right proportions - Earths air is 21 percent oxygen, so any biosphere on Mars would have to perform a constant juggling act between plants and life support. Oxygen is also infamously combustible, adding more potential danger to the astronauts. With all the hazards it would seem to be a prudent plan to drill into the Martian rock and make our bases subterranean. Putting solid rock between people and the spaceborne subatomic particles that pose such a radioactive threat to our cells and DNA would make sense, and underground people and equipment would be less subject to the temperature fluctuations from day to night. The cost would be even higher; Lots of things are different but the rock is still the same as on Earth and all heavy drilling equipment adds to launch weight.
The Space Shuttle was supposed to be the starting point for a new age of affordable reusable space ships, The extraordinarily high cost of the disposable Saturn V moon rocket leading to plans for a more affordable way into space (all of mighty machine ended up either at the bottom of the Atlantic ocean, burned up in the atmosphere, or orbiting around sun, depending on which stage it was). The original Space Shuttle was drawn up as two winged rocket planes launching vertically from a conventional launch pad, the space ship portion piggybacking on the bigger booster, that part flew back to land on a runway. In the end this option was discarded as too expensive, and the Orbiter eventually made it into space in 1981 strapped to a more conventional rocket booster and disposable fuel tank.
The Shuttle made a great contribution to the building of the ISS, and for encouraging greater cooperative ventures with the Russians, as well as being the first space mission for many new countries astronauts, but in the end it was a one trick pony. Incapable of being adapted to any uses other than carrying things to Earth orbit it was retired in 2011 after 30 years of solid but unspectacular service. In the eighties the Russians had a go at a Shuttle too but their Buran craft only took one automatic flight before they ran out of money. Funding has always been the sticking point for any reusable spacecraft project; by its nature a huge pile of money has to be paid up front in order to save money later down the line and nobody has been willing or able to foot the bill. The British aerospace industry proposed a craft called HOTOL in the 1980s, essentially it was a giant space shuttle with a removable module in the middle. Unlike the shuttle it would have been unmanned and would have flown to space with one happen in one engine; an ingenious hybrid of jet and rocket, using an air intake and turbine to drive provide oxygen from the atmosphere to mix with hydrogen in the fuel tank and create rocket thrust. The benefit of the plan was saving a.huge amount of weight by removing the huge liquid oxygen tank that The space shuttle had to carry. The problem was the concept was too complicated to bring to life with the money available. The the HOTOL plan never took off, but the technology lives on in a new Anglo-European project called Skylon, aiming for the same kind of space plane concept.
Even the United States treasury could not bring itself to fund the original Space Shuttle idea and ended up with an complicated mongrel of new and old technology, and needlessly oversized thanks to the intervention of the military. Now the immediate future is an Apollo style rocket; the Nasa Orion moon and mars vehicle now in construction is almost indistinguishable to the layperson on the outside from the Apollo command-service module. Outside of Nasa things are a becoming bit more creative. The SpaceX company has run several successful trials of a vertical takeoff rocket that lands back on it's base on a floating platform. But developing a fully functional space plane may be harder than assembling parts in orbit from the kind of automated rocket delivery craft that supply the ISS. Virgin Galactic, once hyped as opening the era of mass space tourism, have been developing their prototype passenger suborbital mission for the best part of a decade. So our journey through the solar system might one day begin aboard a hybrid space plane, taking off from a familiar runway but for practicality's sake it's likely that all the components of a space station and an advance base in orbit will get their via conventional disposable rocket.
120 billion dollars is a rough estimate of the cost of a small, Apollo like, pioneering mission to land and live on Mars. More still needs to pass to bring the size of the endeavour within our grasp, and more work needs to be done down here on Earth. Not that the work is not being done, on the contrary large parts of Nasa and other agencies are given over to getting us Mars-ready, and now private enterprises such as SpaceX are taking up the work. 'Moxie' is an example of the kind of work being done - heading up into space attached to Nasas scheduled 2020 mars rover, the Mars Oxygen In-situ resource Experiment is a box of tricks designed to synthesize oxygen from carbon dioxide. It is only compact - the size of a briefcase - but that is the purpose; should it work the experiment could be used as a portable oxygen supply for humans.
Over the years of the Space Shuttle, Mir, and now the International Space Station much knowledge has been gained about living long term in space. We know that the human body goes through the wringer in zero gravity- muscles atrophy without the effort of holding us upright, blood doesn't sink to our feet but pools around uncomfortably in our heads. Mars has about own seventh of Earths gravity, so some of these problems might be slightly alleviated, but then we add in the effects of living in a sealed tin can with no natural atmosphere. Even something as basic as sweating becomes a problem - long term astronauts need to exercise a lot to make up for the lack of gravity's tug on muscles, and the lack of all the light activity we do on Earth. With exercise comes sweaty exertion and on Earth that sweat evaporates into the air. In a spaceship it has to be laboriously mopped up.
Even unlikely medical complaints start to arise without gravity; anaemia and potential kidney failure being the most serious that can arise due to prolonged low gravity. All of these complications put a more positive spin on humanity's long stretch without leaving the Earths orbit and the yawning chasm logistics and challenge between visiting our moon and Mars, and why the moon was conquered in a.few short years in the middle of the 20th century and yet Mars has proven to be a much tougher nut to plant a flag in. It is so much further away from the safe haven of Earth, receives less solar energy, and is just as harsh an environment as the moon with some unwelcome differences thrown in.
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Life on Mars
Flying a manned mission to Mars sounds interesting and exciting from an exploration and scientific point of view, but a few brave scientists hunkered down in bunkers growing plants and admiring the views hardly seems like the basis for a second homeworld for humanity. Why not, the thinking goes, make this frozen, barren place, a bit more like the Earth? Terraforming, the theoretical process of turning a desolate rock in space into a habitable world for life has long excited the imagination of writers, movie directors, comic book artists, and real scientists alike. After all, we know he earth was once an inhospitable planet but it came to be habitable through natural processes, we know the composition of our atmosphere, and we know that the elements within are abundant in the Universe. We also know only too well the effect of carbon dioxide in creating global temperature increases. Once we have our Mars bases set up, the next step seems clear; start pumping oxygen, nitrogen and co2 in to the sky and get building Earth Mark 2. Or, rather something more like Mars Mark 1, when the red planet had liquid water on the surface carving out all of the great canyons. Liquid water wouldn't stand a chance in the planet's current frigid state, some freezing in short order while most of it, counter-intuitively, boils away in the low pressure environment, the constituents then dispersed by solar radiation. So bringing the temperature up would have to be the first stage of any terraforming process, and we do that by thickening the atmosphere, in the process hopefully not ending up with a runaway pressure cooker like Venus. There is a moral quandary to this; could we stand to possibly destroy any native bacteria that may live in the soil somewhere on Mars? And is it our right to radically change an alien world to suit us anyway?
In the case of Venus, we might not have such problems in radically altering the planet's atmosphere. There is surely no life there; Venus's heat is not only sufficient to boil away any water that might support life, but hot enough to melt metal. The first photos of what looked like snow on the top's of Venus's mountains confused the scientists who saw them; eventually they worked out that the lighter patches they could see were large deposits of metal. The minerals galena and bismuthinite found in surface rocks had melted to fine mist and rained there. The only hope would be terrorforming somehow reconstituting the superheated soup into something more tolerable. Maybe one day in the distant future we will develop the technology to dispel the broiling clouds and make the planet habitable, and the notion that Venus might once have been a hellscape could become as alien as the Australia or America being Terra incognito.
Recent reinterpretions of data sent back by the two Viking landers puts a new spin on what they found, or rather what they didn't find. The lack of organics seemed to slam the door shut on Martian life, but now researchers think that chemical reactions on the Martian surface could have broken down organic compounds, hence the lack of evidence found by the Vikings. Now the newest generation of landers are being fitted with far more advanced instruments, to detect both the direct evidence of life processes- proteins, amino acids, lipids - and the indirect microscopic evidence. The hope being that if there is, or was, life there, or in other places where other probes can be flown, we will know definitively rather than spending forty years debating the issue, as we have with the Viking landers and other missions.
As with all other human endeavours, the wish of taking sightseeing trips to Mars, or making the planet habitable will eventually come true by way of combination of inventions and innovations, but as for the timescale, we cannot say. In the same way that, for example, the early builders of steam carriages in the 1800s might have reasonably expected to be driving their own cars within a few years, we cannot really predict where we are going. We know that with a reasonable covering of plants it would take Mars several thousand years to build it's own breathable atmosphere, and even when it did over many millions of years it would eventually dissipate just as it did before. But what other inventions will we come up with to speed up the process in the meantime?
Maybe one day the inner solar system will be filled with tourist ships visiting from a Moon base, or underground science labs, or giant installations pumping oxygen into the Martian atmosphere, or removing the co2 from the Venusian sky. Maybe we will make workable fusion power to make an artficial Sun over other planets and moons, or use such power sources to light and heat huge artificial environments inside domes, or on the inside surface of so-called "shell planets", or "Dyson Spheres". For all the flights of fancy from theorists and writers both, what we can be sure of is that there are some things we can't ever change. Even if Mars could be tamed and made habitable the gravitational force on the surface is a third of Earth, the year is twice the length, and the Sun much smaller in the sky. On Venus the retrograde spin means the Sun traces a path from west to east. The year is much shorter at 224 days, but the day is longer than the year, 243 days for the planet to slowly spin backwards (as we would consider it) on it's axis. Nobody knows why Venus spins the 'wrong' way, the only realistic idea is the usual culprit for much of the variation in the solar system; an ancient cosmic collision knocking it round. Any way we look at it, Earth looks remaining the centre of human civilisation even if we end up spreading out to neighbouring worlds.
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Sightseeing
In 1970 in the wake of Apollos 11 and 12 there were predictions of a mission to Mars in the 1980s. It seemed only a matter of time before great space cruise liners were taking the lucky few to see the wonders of the solar system. We are still waiting and with all the super high resolution images coming back since the Venera and Viking landers in the 1970s it is almost possible for us forget that no human eye has ever looked at another planet from close up. The nearest effort has been the Moon and that has only been seen by the twenty four Apollo astronauts who left Earth orbit. Only three; James Lovell, Eugene Cernan and John Young, saw the view twice. The crew of Apollo 13 hold the record for being the humans who have travelled furthest away from the Earth.
And all these astronauts are the only people to have ever seen the far side of the Moon in person. On Earth we always see the same side as the moon is tidally locked by gravity to it's host planet (meaning the rotation of the moon takes the same time as the orbital time), as most moons are. To be the first people to see Mars or Venus up close would doubtless be a profound experience for those who may one day do it. The Apollo crews reported that there were far more craters on the moon than we see from Earth, and far more shades of grey and black rocks and dust on the surface. The stark contrast between moon and black space was striking, and unlike the view seen of Earth from orbit. When left flying solo around the Moon while the other two astronauts walked on the surface the command-service module pilot could gaze upon a view far more stars than visible on Earth. When in the moons shadow the view, in the words of Apollo 15 pilot Alfred Worden, was a 'sheet of white', as the interfering light of the sun was blocked and yet more stars came into view. When coming around the Moon they then saw the Earth rise over the horizon, sometimes in deep crescent shadow as we usually see the Moon.
Such sights would only be more awesome from orbit around Mars as the Earth and Moon shrink to the size of a bright star in the sky. Whether or not the Apollo format would be followed - with two flybys before a landing - or whether we would go all in straight away depends on a great many things, money being one of the highest factors on the list. The new Nasa Orion craft is being designed with both the Moon and Mars in mind. Using technology from both the Shuttle and Apollo eras, the planned SLS (Space Launch System) will be the most powerful rocket ever flown, as it will have to be to get to all the hardware into space. Like the ISS the interplanetary voyager would have to be assembled in orbit over at least two launches, with the crew joining aboard their own smaller ferry flight. The initial plan is to send a flyby mission to Mars using the Orion habitat module as a proof of concept.
The habitat is planned to keep a small crew of two to four alive for over two years, there and back. The long duration comes about thanks to the plan to fly to Mars by using the gravity of the Sun first to accelerate without as much fuel, as the Mariner, Venera probes did.That of course means flying inwards first towards the orbit of Venus before setting course out to Mars. Timed just right the Orion ship would speed up considerably, slingshot around Mars, just as Apollo 13 did with the Moon, and start heading straight back home in only two thirds of a year. By this time the Earth would have overtaken Mars as we have the shorter orbit, so the return leg would set course for Venus again and get another big gravity pull to catch up with the Earth. All very clever and thrifty with fuel, but the downside is that there is only a small window to send down a lander, and if it were to be crewed the astronauts aboard would have to watch the other half of their ship disappear off into the distance.
Splitting the different stages of a mission will probably be the only realistic chance of getting footprints in the Martian dust without breaking the bank. The flyby mission would likely be the first step, followed by unmanned missions to deliver hardware to the surface. When the big moment finally comes for someone to step down and walk on Mars it likely won't be an untouched wilderness they face, but a pre delivered habitation base, with a living module, and a ready-to-fly ascent stage already there. This approach would also be safer; it might be a tremendous anticlimax if the Martian expedition has to abandon after only a few hours, but chances are higher everyone will come back alive.
The kind of long term isolation that comes with the territory has been a source of earthbound fascination for researchers - the Biosphere projects in the 1980s and 1990s built a self contained compound in the Arizona desert. The Hawaii-based HI SEAS (Hawaii Space Exploration Analogue and Simulation) experiments keep six people isolated atop a volcano for a year, only allowing them to step outside of their faux-mars base for 'spacewalks' if they had a full space suit on. They get to.stay in communication with the rest of the world, but only with a.built in delay both ways of 20 minutes, as they would get on Mars. In Russia between 2007 and 2011 there was the 5 year Mars 500 program, a collection of five sealed modules (This time indoors rather than up a mountain), three simulating a base, one a landing craft and one large space doubling for the planet surface. The final trial of this experiment saw six 'crew' staying locked in for a year and a half running through an imaginary but highly realistic Mars landing mission all the way from Earth and back. The experiment trialled technical procedures but was just as useful for seeing how the people inside performed when cooped up together to work through their mission. Just like a real space programme all were volunteers, and naturally inclined to be physically ready and mentally willing to experience the hardships and difficulties. Still, even such hardened specimens found it hard to shake instinctual reactions to being in the confined environment; most found the constant routines and close proximity to the same surroundings and five people tiring and stressful. And that was in an experiment, not years away in space. Recently we have come to find that one of the biggest challenges of interplanetary missions is keeping the crews mentally fit rather than physically in shape - something science fiction.authors, with their takes of astronauts going stir crazy in space, have long realised.
Even if it turns out that Mars is now a lifeless rock, it is still a spectacular rock. If nothing else, the inhabitants of future centuries may take tourist flights to Mars simply to gawp at it's immense geography. When the Mariner 9 craft first overflew the planet, dust storms on the planet obscured it's surface but the tops of volcanoes could still be seen above the dust clouds. The largest Martian volcano, named Olympus Mons, stands fifteen miles above it's surroundings, three times the height of Mount Everest. It is 370 miles across, so it's not quite the same pointed shape as Mount Fuji or Mount Vesuvius, in fact Olympus Mons would have to be viewed from high above, the curve of the Martian horizon would obscure the view from the ground. Much like a human on Earth doesn't notice, for example, the elevation change across the great plains of the American midwest that put Denver Colorado a mile above sea level, then the ground based Martian explorer would not see the rising ground of Olympus Mons, and would not see any meaningful view from the top. Three thousand 'Earth miles' away from the great volcano would be a sight well within the realm of a solo viewer, standing on it's edge; the 'Valles Marinaris', largest canyon known in the Solar System. 2,500 miles long, it would span the entire United States if plonked down on the Earth, and is four times deeper than the Grand Canyon. The really spectacular part is the shape. Though no ground based explorer has yet taken an image from the rim, overhead mapping data shows the canyon has a square profile, with much of the depth taken up with a near straight drop to the bottom. Though the widest parts would be a stretch to see the canyon is still much longer than it is wide, making the view very spectacular indeed for whomever will be the first to see it in person. Perhaps that individual has already been born?
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Jupiter
Long before there was Cape Kennedy and Russia's Star City, the Jet Propulsion Laboratory and the Arecibo Radio Telescope, there were the great renaissance cities; Florence, Venice, Amsterdam. The places where astronomy as a science really began were hotbeds of trade and money, where a rich merchant class could indulge their passions for learning, discovery, and, of course, money making. The one led to the other, especially upon the seas where the trade routes were defined by technology - faster sailing ships and better navigation. Navigation and timekeeping were practical uses for starwatching, as following the stars was usually the only way for a ship captain to know where and when he was going. Along with watches and clocks, the age also saw the birth of the microscope and telescope, allowing those who could afford them the chance to look at the very small and the very large structures of the universe for the first time. Magnifying optics allowed, on January 7th 1610, for a Venetian, one Galileo Galilei, to look at the planet Jupiter, and see that it had four moons.
Though Galileo wasn't the first observer to look closely at the planet with optical assistance, he was the first to see something in the universe not obviously orbiting the Earth. Though it was xxx years after Copernicus his theory was still on the fringe, and it was not not only because of suppression by the authorities, though proposing that the sun was the centre of the universe did not fit in at all with church doctrine at all. More skeptical - and possibly less God-fearing - thinkers also had arguments against; Tycho Brahe advocated his system of the universe partly because of parallax - the clear difference in perception when moving around between near and far objects. The universe would have to be truly enormous to account for the lack of parallax, and the distant twinkling worlds emitting the light would be far larger than our own sun. Neither Tyco Brahe or Johannes Kepler had the use of telescopes of course, and even many relatively enlightened thinkers could not make the leap to such a huge empty void between the worlds of the heavens. In the popular imagination, Galileo's revelation of moons orbiting something other than the Earth, led to his condemnation by the Catholic Church for heresy, a trial before the Pope, and his house arrest for the rest of his life. Things were a little more complicated than that.
With his telescope he could see faint details of an Earth-like surface on Mars. He pointed the telescope at Venus and saw that it had phases like the moon. Looking at Saturn the planet seemed to have 'ears' (as he put it), but only at certain times. It seemed as though it changed shape throughout the year. These observations did not lead by themselves to conflict with the Church. It was 1615 when the Roman Inquisition under Pope Paul V first seriously investigated Galileo. He was told he could continue working, and writing about alternative theories about the universe, just as long as he did not claim that any of it was true. Eight trouble-free years passed, a new Pope was installed. This man - Pope Urban VIII - was in fact a personal friend of Galileo.
In the end it was twenty years after his observations that the astronomer and cleric finally came into terminal conflict, and then only because Galileo made a very unwise decision. At the time it was common to write about scientific ideas in the form of "Dialogues", a type of fictional imagined conversation between two people that dated back to the ancient philosophers. The advantage of this type of writing meant that it fitted the bill perfectly for any thinker who wanted to avoid being thought of as propagandising for heretical ideas. His dialogue on the motion of stars and planets, published in 1632, naively placed the words of the Pope in the mouth of a foolish character called "Simplicio". This slight infuriated the Pope and lead to the famous trial for heresy and Galileo's eventual house arrest and forced recantation of his words, by which time he was an elderly man. In truth although the trial was a personal ordeal for Galileo, and doubtlessly shortened his distinguished life, it did more for his legend than anything else could have. Time proved him right and the Church wrong, and the prosecution went down in history as the greatest example of dogma suppressing facts. Galileo's legendary words, supposedly muttered to the inquisition when they insisted on the Earth being the static centre of the universe - "Il pure muove" (And still it moves), is practically a catchphrase for the importance of science, even if whether he actually said any such thing has been lost in the mists of time.
The number of known moons of the two planets has risen from the four Galileo could see, to many tens. In the 1970s and 1980s the four deep space probes Pioneers 10 and 11, and Voyagers 1 and 2 provided the first close-up images of Jupiter and Saturn, and much of the data about their nature. The Voyager missions were designed to make the most of a rare alignment in the orbits of the outer planets in 1977, that would allow the spacecraft to slingshot around Jupiter, gaining a great deal of speed, before performing a similar gravity-assist around Saturn to head to Uranus and Neptune. The spacecraft themselves were built to a fulfill a very demanding brief; even with the fortuitous arrangement of the planets, it would take twelve years to get to Neptune. Twelve years for the craft to work perfectly, as they were a long way from anybody who could repair them. NASA also had to organise what they called the "Deep Space Network" - an organisation of powerful radio transmitters and receivers all around the Earth to communicate with the spacecraft. The Pioneer 10 and 11 craft were the precursors to the two Voyagers, the first spacecraft to pass beyond the orbit of Mars, and made the first encounters with Jupiter and Saturn, discovering along the way the intense radiation emanating from the former, a useful lesson learned for the construction of the Voyagers. Without that knowledge it is likely much of their instrumentation would have been damaged by the radiation without shielding.
The Pioneers gave fuzzy nearby images showing the colours and patterns of the moons, blurry pictures like a short sighted person squinting without glasses. The Voyagers really opened the curtains, transmitting back stunning clear photographs of the moons orbiting the planets. Tipping a hat to their discoverer the major mission of the 1990s dedicated to exploring Jupiter and Saturn and their moons was named Galileo. Launched in the payload bay of the Space Shuttle 1989, after spending the whole decade assembled and waiting to lift off while delays snowballed on top on the mission, Galileo could take pictures at much higher resolutions than the Voyagers, had cameras for UV and IR, radiation detection, magnetic detection, and could collect and analyse all kinds of elementary particle that came the spacecraft's way. Galileo also carried a smaller cone shaped probe to drop through Jupiter's atmosphere, on an hour long plunge through the planet's atmosphere, the larger spacecraft acting as the radio relay to send back to Earth whatever data the probe recorded. The probes transmissions lasted for one hour before the thick hydrogen broth of Jupiter's atmosphere destroyed the radio equipment - estimates put the time the probe lasted before being dissolved away like a boiled sweet at about ten hours. The designers and engineers of the probe had done a remarkable job of building an object that could survive that long in the crushing pressures and temperatures of its surroundings. We are used to Earths atmosphere turning returning space vehicles to white hot projectiles as they smash through the air, but this is a walk in the park compared to Jupiter. During its drop the Galileo probe was slowed from 46kph per second (or 165600 kph - a speed that would lap the Earth four times in an hour) to a crawl in four minutes. To avoid contaminating the Jovian moons the original spacecraft was also disposed of this way when it's power finally ran down.
Today we know that Jupiter and Saturn are both huge spheres of hydrogen and helium, bound together by gravity. We know that they are so huge that the gases are compressed into a liquid and then near-solid state further inside the planets, and there is probably a solid core hidden inside them larger than the Earth. We can speculate that in the deep and distance past at the formation of the solar system Jupiter may have come close to becoming a star in it's own right, leaving us with two suns in the sky, but it did not become massive enough. As it is it generates it's own heat and magnetism, our radio telescopes pick up huge radio emissions from Jupiter, the radiation around the planet thousands of times greater than the Van Allen radiation belts around the Earth. The 'magnetosphere' of Jupiter exerts a huge influence into space; if our eyes could see it Jupiter's magnetic field would be as huge in the sky as the sun. Galileo's 'ears' are, of course, the great rings of Saturn, and the movement of it's orbit relative to our view on Earth explains it's changing appearance.
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The Moons
It is probably safe to say that it is unlikely humans will ever venture far into the the atmosphere of Jupiter, we will have to content ourselves with exploring the moons. Not a bad outlook, as it turns out, given that the information send back.by our robot probes has shown that the moons of the great outer planets are far from being second best to their host worlds. The inner three planets have been frustrating for our hopes of finding more than barren rocky worlds in the solar system, while the outer planets are gas spheres far too cold and remote from the sun to possibly sustain any life... at least that is what we once thought. The Jovian and Saturnian moons represent a glimmer of hope of finding something really exciting in our solar system. Dreaming of life on Venus and Mars has been replaced by wondering at pictures from the moons. They are mini solar systems in their own right. One of the moons of Jupiter, Ganymede, is larger than the planet Mercury. Another, Io, shows the only sign of active volcanoes in the solar system outside of the Earth - the volcanoes on Mars are all clearly extinct, and the ones on Venus have never been seen to be alive.
Io
Known for several centuries as a distant shiny dot, then partially unveiled by Victorian astronomer Edward Barnard, who observed the patches of different colour and brightness, Io was finally revealed by the Voyager spacecraft as a tiny moon covered in volcanoes and mottled all over with lava deposits. The first grainy images received by the mission scientists on Earth of a huge structure towering into space from it's surface caused much debate before it was agreed that the cameras had caught sight of the sulphur dioxide plume from a volcano, unencumbered by an atmosphere, throwing material high into the sky. Io was arguably the most extraordinary and unexpected thing discovered by the Voyagers; Just one big question came to mind for the scientists - how did such a tiny moon have a molten interior like the Earth? And the second question was why this place in particular but not anywhere else? The best answer comes from Io's proximity to it's giant home planet, and the enormous gravitational forces it endures. Where the Earth's moon pulls the oceans around to form the tides, Jupiter pulls at Io so forcefully the friction heats the interior rocks up enough to turn them molten. The effect is magnified by Io's erratic orbit - we can count ourselves fortunate we are on a planet that has a relatively stable orbit or it might be as uninhabitable as Io.
Europa
Europa, the smallest of the four major Jovian satellites, is an ice world, smoothed snooker ball smooth (or so it seems from a distance) by the frozen coating. There are no craters, only cracks and fissures in the otherwise smooth ice surface. The contrast with Io could not be more stark - it seems as though the less intense tidal forces Europa is subjected to leave it relatively quiescent compared to its volcanically lively neighbour. That is not to say that tidal forces don't have a significant impact on the moon. The surface temperature is minus 160, but the ice layer, it is thought, gives way to a liquid ocean underneath, the heat provided by the immense amounts of energy exerted by Jupiter's gravity. There is probably more water here than on the Earth, and the oceans are deeper too. And heat plus huge amounts water naturally gives rise to the question of life. While the radiation would still be too high for unprotected humans to live on the surface, Europa is likely to be warmer than other moons that could have subsurface oceans and is considered by many experts to be the best place of finding extra-terrestrial life aside from Mars
The probability of finding life on these alien worlds has been given a boost by discoveries closer to home, in worlds almost as alien and unexplored as the ones in space. In the deepest depths of the world's ocean floor we find volcanic stacks pumping superheated water, minerals and coagulating with bacteria thriving in the boiling oasis in a way that would have been thought inconceivable had our ocean explorers not scooped up the proof. Similarly in the blackest and dampest corners of the world's caves are pools of life existing happily without any interaction with the sun at all. Pools of slimy bacteria is not quite alien life we imagine or wish for but it's discovery would be profound; finding that even in our tiny fragment of the Universe there are two sources of independent life would suggest that the universe as a whole must be fairly well populated with organisms of some kind. Since we have not managed to send a sample of Mars back to Earth, yet alone the far further away worlds around Jupiter, this discovery might take us a while. Though the estimated cost of building a craft that could drill into the ice, or swoop through any plumes of water ejected from the surface and send some of it back to Earth, while into the billions of US dollars, would be small fry compared to say, the cost of keeping the military going for a few months.
There's not much sign of anything larger on these moons - unsurprising given the Jovian radiation fields, less harsh than Io, but still enough to give any human (or human sized animal) on the surface a fatal dose after a days exposure. The radiation problem might be solved by ingenuity one day - after all we didn't even know what radiation is until 120 years ago - but for now it seems impossible that if there was life on Europa it would be anywhere other than in the subsurface ocean. The dramatic cracks and fissures on the surface are caused by tidal forces, though they are not as uniform as we might expect given how Europa always faces the same direction facing Jupiter. The rock solid ice surface sits far below freezing temperatures, but if it hides an ocean the consequent dynamism might explain the mess of tangled cracks and marks leading in all directions across the surface.
Callisto
Jupiter's other two large satellites are also probably concealing large subsurface oceans. Ganymede and Callisto look like solid rock. Callisto in particular has a sparkling jewelled surface, like polished granite. Yet the ancient exterior - so thoroughly pockmarked with impact craters astronomers consider the moon to have the oldest unrefreshed surface in the solar system - contains an interior of much less mass than an equivalent sized rocky planet with a molten core. Subsurface oceans are the best bet to explain the lack of mass. The question naturally arises of how we can possibly know this, given the dull dark surface of the moon, millions of kilometres from the Earth has never felt the touch of any robotic lander. The deduction comes from probes studying the effect the moon has on the magnetic fields of Jupiter flowing through it - Much like the studying of Earthquakes and electromagnetic waves tells us about the composition of our own world. There is clearly something highly conductive within a moon like Callisto that blocks much of the magnetic radiation. Because it is outermost of the Galilean moons Callisto receives much less of a radioactive smothering than Io, Ganymede and Europa, and less even than the Earth gets from the Sun, making it the best prospect that humans could one day pilot a lander to. Though those far off astronauts won't see much in the way of scenery on the surface as the ancient moon has little in the way of terrain. The best view would be from above, looking down on craters like Valhalla and Asgard - giant impact zones measuring thousands of kilometres across, not reaching great heights but covering an area the size of western Europe in clear concentric patterns of debris unchanged for several billions of years.
Ganymede
Sitting between Europa and Callisto, Ganymede is the largest moon in the solar system. In fact it is larger than Mercury too, and it bears a resemblance to that planet our Moon. Any astronauts flying towards Ganymede might get a strange sense of familiarity, like seeing a long lost family member for the first time. The darker more ancient areas of Ganymede are estimated to be a similar age to our Moon too - around 4 billion years - and like the moon the majority of the cratering is probably from that era, tallying with the theory that the solar system in that time was still a sea of asteroids and floating debris. Ganymede is the only planetary satellite with it's own magnetosphere, meaning that it has an internal iron core, like all of the rocky planets. Compared to its host planet the magnetism it generates is minuscule, hence the reason why it took the Galileo probe flying close by to discover it. The presence of aurorae over the surface also gives the game away, like on the planets the atmospheric light show shows the magnetic field. Galileo's spectroscopy instruments revealed that there was plenty of water ice on the surface, as well as more evidence of an unseen subsurface ocean in the deposits of sulphates. Curiously the surface craters are less defined than on many other moons, suggesting the surface has been less than solid in the past.
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Saturn
Saturn is the next stop on the outward journey, but it's no brief jaunt from Jupiter to get there. The second largest planet is nearly as far away from its giant neighbour as we are. Saturn is a good 11,000 kilometres smaller around the equator than Jupiter though the great speed that it rotates - Saturn does a complete spin once every 10.7 hours - causes it to bulge out by an extra ten percent around the middle. The giant planet is mostly hydrogen and helium like Jupiter, but the distinctive light beige colour comes from large quantities of ammonia diffused throughout the upper atmosphere. The seasons on Saturn take seven years each to cycle and being much further from the Sun makes the year much longer at 29 Earth years.
The fabulous rings; the 'ears' that Galileo spied at the beginning of the 17th century, are giant discs of rock and ice. We will never know for sure what event began the formation of the rings and when exactly it happened. What we are sure of is that the rings are huge - at least in one direction. Infra red surveys from spacecraft have shown that if we could see all the matter caught in the rings we would see a disc 200 times the size of Saturn. This giant wheel would be an astonishing sight were we able to see it, dwarfing the planet at it's hub. It also explains why the small grey Saturnian moon Iapetus has a mysterious blackened side; it is stained by dust from the extended rings while passing by the planet in a lopsided orbit. This eccentric path means that any explorers standing on Iapetus would get to see Saturn and its rings from an angle - all the other large moons are on the same plane and get a much less photogenic view directly side on.
The closer observations of the space age have shown how astonishingly thin the rings are; around ten metres. Some portions do spread out wider, up to a kilometre, but much of the huge rings are about the same height as a three storey building. An obvious idea for where the rings came from is that they are a smashed moon distributed into pieces. Set against this though is the curious fact that most of the matter in the rings seems to be water ice rather than rocks. Yet the recent discovery that some of the moons of Saturn could have large amounts of frozen mantle under their surfaces again makes this idea plausible, perhaps the icy rings are indeed a pulverised long lost moon. It could also be that some disruption in the nebula of dust that became Saturn caused the rings to be formed at the same time as their host planet, or they could be the result of a collision in relatively recent cosmic history; only a few hundred million years ago. Nobody is quite sure.
Even without it's halo it would be a pretty interesting planet. Studies show the huge sphere is less dense than the equivalent volume of water would be - leading to the curious image that Saturn would float on your bath provided it was a few million kilometres across. The featureless beige atmosphere looks much more lively viewed through more powerful magnification. Violent storms do spread across the surface often with great speed. In 2010 Cassini photographed a huge churning rupture in the clouds, an enormous tear in the surface that appeared in hours and soon circled the whole planet. Underneath the storms also drop down hundreds of metres towards the hidden depths of Saturn's atmosphere. Enormous amounts of electrical charge is generated; massive lightning bursts have been seen in these storms. The biggest feature on the surface is on the north pole where a storm in the shape an almost perfect hexagon rages. This is the Saturnian equivalent of the great red spot of Jupiter - it never shows sign of fading, it was there when Voyager 1 flew past in 1981 and it was still there to greet Cassini twenty years layer. How the storm system maintains it shape and six straight sides despite being the size of four Earths is a mystery, but computer models allow researchers to come up with a good estimate of what is likely to be going on underneath the hexagon storm.
The Pioneer and Voyager probes took the first close up photos and readings from Saturn as they did Jupiter, but the biggest contributor to knowledge about Saturn has been the Cassini probe. Launched in 1997, and first encountering Saturn in 2004, Cassini was built with the intention of flying around the rings and moon for four years, with the Huygens lander being dropped into the atmosphere of Saturn's largest moon titan. The Cassini-Huygens probe was named for the two great early astronomers who made many early discoveries about the planet and who moved things on a huge distance from where Galileo left them; Giovanni Cassini and Christian Huygens. Cassini, born in 1625 in what is now north west Italy (then one of the separate Piedmont Duchys), spent half of his life in Paris, working as the French royal astronomer. Before moving to France he was head of the university of bologna, and while there acquired solid observational evidence that the size of.the sun in the sky regularly fluctuates, confirming via an ingenious pinhole camera observatory that the Earth orbits the sun in an ellipse and not a perfect circle as Kepler had theorized. While in Paris Cassini discovered four of Saturn's moons, the large gap in the planet's rings that also bears his name, and independently observed the great red spot on Jupiter (he shared the credit with English astronomer Robert Hooke). He also spotted that some of the cloud.layers on the planet were moving in different directions to each other, centuries before the Pioneer probes gave us the first close up.look at the atmospheric motion.
Huygens was born into privilege and culture, the son of a diplomat who home schooled him in the sciences, arts and sport. Young Christian was a 15 year-old with an extensive reading list of science and philosophy who's father knew some of the great scientific minds of the age personally. so the young man could chat with the men who wrote his books. He was a very clever young man in the right place at the right time and he put his early advantage to good use, studying mathematics and law at university and becoming a professional polymath. As well as making huge contributions to maths and physics - he was ahead even of Newton in thinking that light was a waveform not some form of particle - he came up with inventions; the pendulum clock was one of Hugygens great innovations. The same clockwork mechanisms allowed Huygens, among many others, to build working models of the solar system. These 'Orrerrys', as they were named, could be incredibly detailed. Miniature brass facsimiles of all the known planets orbited their own sun, carried aboard tiny wires mounted on intricate gears, with their own little moons. As well as being impressive ornaments they had real scientific use - a kind of primitive mechanical computer simulation.
His other great lasting contribution was in optics and lenses. In 1662 his telescopes allowed him to see the rings of Saturn more clearly; he theorized on the true nature of Galileo 'ears', noticing that they did not touch the planet's surface and seemed to take an ecliptic orbit. Looking through his telescope he could also see that Saturn had a moon, the first sighting of Titan. In 1661 he recorded in detail a transit of Mercury across the sun. On Venus he saw the clouds of the atmosphere. Observing Mars he could see different coloured surface features. We know them now as volcanic plains but although he could not know this Huygens had an imagination far ahead of his time; his discoveries led him to publish a book in his late middle age called Cosmotheros, in which he imagined what life on other planets might be life. If, he thought, these dark patches on Mars were Oceans then there should be no reason why there might not be creatures swimming around in them. This was pretty out there stuff for the 17th century, an age still ruled by strict Christian theology. A theology that was purely based around the Earth's inhabitants and those who watched over them in the heavens. That there could be worlds out there that God had also populated with life was not an idea that came easily. When for example, tales were told of strange visitations in the night they told of demons and unearthly spirits not alien invaders. Fortunately those early astronomers did not shrink from the rather humbling discoveries they made, and accepted the fact that earth and its neighbours could be more similar than people had ever given thought to before. Not only was what we knew changed forever, but how we think. There is a reason after all that these scientists have space craft named after them centuries later.
In the end the Cassini mission achieved all of the above and was so capable it was kept alive for Another decade, finally ending with the Cassini probe itself being flown through the rings and into the Saturnian atmosphere in 2017. The first triumph of this, arguably the most spectacular space mission ever launched in terms if photographs and data received back on Earth, was the landing on Titan by the Huygens probe, dropped from the main Cassini craft in 2005 down onto the moon - the most remote surface landing yet achieved from Earth, and the first landing on a moon around another planet. Photographs were sent back showing the views from the probes parachute journey down to the surface, In an ironic echo of the Russian Venera probes lens cap failures 50% of the images captured from Huygens descent were lost when the camera transmitter on the craft failed. What did come back though was spectacular - a continuous stream recording the entire decent through the thick beige coloured clouds of Titan until the surface features came into view. The vista the lander captured looked a little like Mars, albeit with a much thicker, darker atmosphere. It was the the remotest landing of a spacecraft from the Earth to date. Most excitingly the mission discovered that there were liquid lakes on Titan, but these were not lakes of water but lakes of methane. The very low temperatures make place the element well below it's boiling point.
A manned expedition to Titan is a distant dream, but from the Huygens data we already know it would not be as outlandish as we might think. A human explorer Would not need to wear a pressure suit, just breathing apparatus and some form of heater as the temperature is a perishing minus 179 degrees. Moving around would be easy enough - though larger than the moon the gravitational pull of Titan is slightly lower. We could even theoretically fly a plane in the atmosphere, as long as all the parts could be kept from freezing up. And if explorers landed on the right side of Titan the explorers would be rewarded with one of the most - if not the most - spectacular views in the Solar System. Saturn hangs still in the sky thanks to Titan's orbit lasting the same time as it's day, and at a distance that makes it huge - almost one half of the sky over the horizon.
Tantalizingly neither of the two Cassini craft were designed to detect any of the telltale chemical signatures of life processes. Titan's subsurface ocean is a prime candidate for any microbial alien lifeforms, and now we have seen it's mighty geysers, Enceladus is creeping up on the radar too. These are geysers just like we find on Earth, caused by heated water under high pressure. The water is probably heated by tidal forces rather than tectonics as on Earth, but heated water is heated water either way, and naturally it raises the possibility of life being possible in the water. It happens on Earth after all; the deep sea volcanic vents found across the ocean floors are teeming with bacteria. But even if this moon is sterile and dead it won't be a disappointment. The geysers make ours look a little on the small side - if a space sightseeing ship took a cruise over Enceladus at the same height that an airliner cruises over Earth it would still have to avoid the frozen columns of ice. The ship might also need tinted window since the ice on the small moon in view outside makes it the most reflective object in the solar system. The cracks and stripes of Enceladus are clearer in the images we see in books and websites than they are in reality. like many of such photos of planets and moons the contrast and colours have been exaggerated to show off the features. Similarly most pictures most of is have seen of Jupiter or the surface of Mars are a.little more colourful than they would be in person.
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Uranus and Neptune
Another 1441 million kilometres onwards from the Saturnian system sits the seventh planet. Uranus. The first planet to be discovered in modern times rather than antiquity, through the seven foot long telescope of William Herschel in a garden in Bath, Somerset in 1781. Though now we know where to look it is clear that Uranus is visible to the naked eye in the night sky, but because it takes 84 years to orbit the sun, and is further from Saturn than Saturn is from the Sun, the planet was barely distinguishable from the background of much more distant stars. And that's what the many people who catalogued Uranus before Herschel thought it was when they observed it. The great British astronomer gets most of the credit for the discovery, despite the fact that he thought the distant dot was a comet, and he gave it the clunky moniker Georgium Sidus, after the King. Additional insight was provided by two continentals; Anders Lexell and Johann Bode, who independently studied the orbit and introduced the idea that the new object was a planet. Bode also suggested the alternative name, to fit neatly into the mythical naming themes of the planets.
With little surface features to see on the frigid sea of hydrogen, helium and methane, Uranus' most famous feature is it's unique sideways tilt and rotation. Though it orbits in the same plane as the other planets Uranus sits on it's side, at an angle of 97 degrees to its orbit and 'rolls' like a huge wheel once every 17 hours. With this unusual orientation the days and years on Uranus are totally alien to us on Earth. The polar 'Midnight Sun', similar to that seen in the Arctic on Earth, lasts 42 years for each pole as the planet orbits the sun with one side facing alternately. Much like Venus's strange backwards spin we cannot know exactly what tipped the planet over but the only known mechanism is a cosmic collision during the early eons on the Solar System. This collision may also explain why the Uranus is much colder than any of or another large planet; the collision blew out much of the core material, lowering the temperature permanently. As always we can only hypothesise with such ancient event.
Though usually called a gas giant, like Jupiter and Saturn, Uranus is better described as an ice giant as only the outer 20 percent of its structure seems to be gaseous. Down the core is Probably methane and ammonia ice. That methane may be the source of an extraordinary ocean we will never see in person. Many planetary scientists speculate that there may be an ocean of liquid diamond, with floating diamond icebergs and battered by diamond hailstones, all hidden deep within the planet underneath the layers of ice in different states. The extraordinary image is conjured up by experiments on Earth showing the same effect happening to methane under high pressure as the carbon inside is crushed out and turns into diamond rain. The diamond ocean might also explain the strange magnetic field of Uranus, which seems to be generated not in the core, where a thick pure carbon sea would block magnetism, but higher in the atmosphere.
Surprisingly for such a large planet Uranus has only been visited once by a space probe; Voyager 2 flew past in 1986. Voyager 1 had been sent to Titan instead, and then missed both Uranus and Neptune. Neptune is another 1600 million kilometres beyond Uranus at its closest point (and over 7000 million when they are on opposite sides of the sun) and it took Voyager 2 twelve years to reach even with the favourable alignment during its mission. Even its light takes four hours to reach us across the enormous expanse of space. Unsurprisingly it took until comparatively recent times for us on Earth to know the eighth planet was there. Though it is several times the size of Earth, Neptune is far enough away to be beyond the sight of human eyes, and even with a telescope is faint and takes guidance to find. Like it's 'Neighbour' Uranus only Voyager 2 has had a close encounter with Neptune. We have relied a great amount on the Hubble Space Telescope and other advanced Earth bound observatories to see details on the planet. Were we someday to be able to see it in person we might be impressed by the amount of activity we can see going on in the atmosphere. After the somewhat featureless Uranus and the beige clouds of Saturn, Neptune has the look of a brilliant blue sibling of Jupiter. There was even a prominent great blue 'Dark Spot' to match the red spot around the same latitude of the southern hemisphere. The storm systems on Neptune appear more transient than their counterpart on Jupiter, however. In the 1990s the original dark spot disappeared completely shortly after Voyager 2 took the first close up images of it, only for a new similar sized storm in the northern hemisphere to appear to take its place.
It took a mere two weeks after the planet's discovery for astronomers to spot Neptune's largest moon Triton. Orbiting backwards from the usual motion of moons, Triton traces the most perfectly circular of all the elliptical orbits in the solar system. It is also volcanically active, this unusual state of being shared with Io and Enceladus, though these two moons are much smaller - Triton is slightly smaller than our moon. The retrograde orbit suggests that the moon is an object long ago caught in Neptune's gravity, as always when and where can only be conjecture. We are overdue to return to the outer planets - even in the current age of outstanding imagery from deep into the universe we only know what 40 percent of Triton even looks like. The moon is in pole position to be targeted by the next mission to the outer two planet', whenever that may occur. Unfulfilled plans have been afoot ever since the Voyager age but since Neptune is an extremely long way away further mission proposals have not amounted to any more launches. The number of 'What ifs' surrounding Triton are a match for Titan. It has frozen poles and a thin nitrogen atmosphere, volcanic nitrogen geysers, and could have interior radioactive heating and a subsurface ocean, leading to inevitable questions about harbouring microbial life. Closer observations are needed, but so is the money, until then we keep occasionally looking Neptunes way in our telescopes.
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Pluto and beyond
Neptune is the eighth and final planet in our solar system, but everybody knows that if we carry onwards further we eventually reach distant Pluto, the small ball of rock that for seventy six of its millions of years was classed as the ninth planet in the solar system. In 2006 the world's astronomers association decided to redefine Pluto as a Dwarf Planet, reducing the number of planets in the solar system back to 8, as it was in 1929 the year before California's Lowell Observatory astronomer Clyde Tombaugh spotted the moving tiny white dot on photographic studies of the far solar system. The observatories founder Percival Lowell tends to get the popular credit for the discovery but it was Tombaugh who did the actual busy work. It wasn't the giant 9th planet many people at the time had been hoping for but the tiny new discovery had an oddity all if it's own - it's strange tilted orbit well away from all the other planets.
This diminutiveness was one of the main drivers in Pluto being downgraded to a Dwarf Planet - the slanted orbit, away from the plane of all the other planets being another factor. But another major influence was the early 2000s discovery of three so called 'Trans Nepunian Objects' - small worlds sat beyond the orbit of Neptune like Pluto; Eris, a rocky sphere little smaller in diameter than Pluto but more dense, orbiting the sun at three times the distance; Makemake, a little smaller than Eris, but brighter; and Haumea, a small oval shaped world. Such new discoveries complicated matters a great deal from the traditional view of the nine planets, leading astronomers to try to define exactly what is a planet and what isn't - something that had never been needed before. Pluto's demotion caused great discussion and argument but it didn't change the fact that little was known about Pluto other than its movements and the fact that it had a small moon of its own.
New Horizons was launched in 2006, with a nine year flight to Pluto ahead of it. On launch ut took the record for the fastest any craft has left the earth, though it was quick out of the blocks ultimately all the gravitational slingshots around the planets still mean Voyager 1 is faster than new horizons. Clyde Tombaugh, the man who first recorded Pluto in 1930, died aged 90 in 1997, and some of his ashes were interred on the spacecraft, meaning some of his (former) atoms are now the most remote human remains in the cosmos. New Horizons looks like a large Gold grand Piano with a satellite dish stuck to it, though similar on size to the Voyagers - it still needed to fit in the nose of a rocket after all - it was stronger and had more shielding against the solar wind. Like most other probes it is powered by radioactive isotopes, though this time computerised controls had advanced enough to allow the craft to be 'slept' for years until it reached it targets. After nearly a decade in space the restarting of New Horizons was one of the tensest days in Nasa history. All went well, but all that really meant was another agonising wait to see if the machine would successfully capture it's target. Pluto had never been seen up close before 2015; in one flyby the one probe sent back several months worth of data streams, including spectacular close up pictures of the (former) planet, showing it's highly differentiated dark and light surfaces. The mission was granted an extension to explore the Kuiper Belt once it had passed Pluto. Named after eminent 20th century astronomer Gerard Kuiper, discoverer of two of Uranus's moons, the methane of Titan, and planner of the Apollo landing sites, this area is thought to consist of much of mass of the solar system, albeit the icy remnants that never formed into planets and moons because of the lack of a source of gravity to pull them together, (ironically their namesake did not personally believe such formation was feasible). There could be a Planet Nine out there, too faint to be seen, as it's possible effects have been seen on the some of the objects. This is a mystery for the future. The kind of distances involved are to be expected at this point - though the first Kuiper Belt objects are 'near' to Pluto, it is still a four year trek to reach the first intercept with one.
New Horizons joins Pioneers 10 and 11 and.the two Voyagers as spacecraft that are heading for interstellar space. Currently only Voyager 1 has left the solar system, passing through that milestone in August 2012 - 35 years after it left Earth. It is travelling at the greatest velocity of our deep space probes and the chances our it will remain the most distant physical evidence of our existence for a very long time. The only way to pass it would be for a giant step forward in propulsion to come along, and even would this one day come to pass we still wont find Voyager 1 - In 2025 or thereabouts the final gasp of its nuclear core will be exhausted and it will no longer broadcast a signal.
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Back Home
While it has been a spectacular journey to the far reaches of our neighbourhood in space, it is also a sobering one; of all the spectacular and curious worlds near ours none are remotely amenable to keeping us alive. The more we discover, it seems, the more work we find it will take to leave our home planet and spread out to live elsewhere. This urge to travel out into space is not just a flight of fancy either, but as many authorities will point out, confining our entire species to one planet leaves us dangerously exposed to being wiped out from an impact from beyond our world. The two most chilling discoveries from our time of exploration and inspiration in the space age are probably the realisation of just how much radiation pours from the sun and how reliant we our on our thin layer of atmosphere to keep is from being fried by cosmic rays, and how powerless we are to act if an asteroid or comet comes heading our way. These rocky and icy remnants of the formation of the solar system still float around all around us, many held in the asteroid belt between Mars and Jupiter but some loose and able to wreak appalling calamity on the Earth should they strike.
As well as the ability to leave the planet to settle on another we would be well advised to develop reliable deep space flight to take more direct action against asteroid strikes on Earth. Though it sounds like a sci fi movie plot there is nothing at all implausible about nudging threatening rocks away from collision with Earth using spaceship engines. The difficult part would be detecting the threat in time to do some thing about it. With the ability to launch ships from earth orbit we would massively increase our chances of being able to do something able the threat from rogue asteroids. And though that threat is quite remote - there are thankfully few big space rocks in our vicinity, something we can thank Jupiter for as it's great gravitational influence on asteroids tends to shepherd them into the asteroid belt away from - we still see the evidence on the surface of the Earth when we know where to look. It can take an expert eye to tell the difference between volcano caldera and impact craters- this mere fact shows the huge power of an impactor. What is surprising is the size of the rock required to create such large craters. The great meteor crater in the northern Arizona desert is estimated to have been caused by a lump of xx xx metres in diameter hitting at xxx. The most famous strike was the one thought to have ended the age of the dinosaurs 65 million years BC, and generally agreed to be in the gulf of Mexico just off the coast of Chixilub. The size of the remains of the crater under the ocean hints how enormous was the impact, but it was the climatic effects that really changed the world and finished off much of the life on Earth- and would probably do the same to us.
So there is a very large incentive to develop lander technology we can rely on, and as it turns out, we are well on the way to achieving this goal. The European Space Agency's Rosetta mission successfully landed a probe on a comet in 2015, eleven years after it's launch from Earth. Comet Churyumov-Gerasimenko was quite close to the Earth - a mere 450 million kilometres away, less than the distance to Mars, when the Philae lander touched down on it's surface and sent back a picture of the comet's surface. It took a decade to catch up with the comet though, as with all comets it is orbiting the sun in a highly elliptical orbit, in this case one that takes it as far out as Jupiter every six years. Rosetta caught up with the comet at it's closest point and then had to intercept an object about the same size as a small country town.
Comets have always inspired a range of emotions in humans almost unmatched in human mythology by any other celestial object. The appearance of the bright wandering stars parallel the development of science and decline of superstition - Once they were seen as portents of ill fortune - the Bayeux tapestry records the appearance of Halleys Comet in the skies above Anglo Saxon England before the Norman invasion of 1066 and even in woven wool the expressions of fear on the observers pointing to the object in the sky are clear. By the 18th century things had moved on a bit - the object had a name, Halleys Comet, named for Sir Edmund Halley, Astronomer Royal, who recognised it's true nature as a recurring object orbiting the sun that had been seen before and had a regular visitation of Earth.
Now thanks to Rosetta and Philae we have seen the surface from up close, though there is still a ways to go with our landing technology; Philae bounced twice when it landed and fell into silence without it's solar panels aligned correctly, curtailing much of the hoped for data collection. Remarkably it's mothership found the tiny lander again a year later, and took some pictures of it, quite an achievement for its cameras when we consider that Philae 'bounced' well over 1km off the comet, twice before coming to a stop. Equally remarkably the small device came back to life again as the comet turned and it's shadowy landing site came back into sunlight, allowing enough power to return for sporadic instructions to be sent from mission control on Earth and some of the instruments to function again.
Some theories postulate that icy comets could be the source of the first water on Earth, but what giveth can taketh away again. Should a comet ever head our way the devastation would be huge, but not entirely unimaginable thanks to the events of July 1994 when we saw an impact of a comet with Jupiter. Comet Shoemaker Levy 9 hit the gas giant's surface, destroying itself and tearing huge impact marks in the atmosphere, some the size of the smaller planets. Though on the far side of Jupiter to be observed from Earth, the Galileo and Ulysses probes were both in position to see the impacts as the comet tore apart and scattered over the surface. The Hubble space telescope meanwhile could observe the 3000 km tall plumes of fire shooting out. The comet strike was probably the biggest event seen in human times since a supernova that appeared in the skies circa 1006 AD, and bright enough to appear in the daytime sky. And even then that was an event that happened around 7200 years earlier given the distance of the star.
The huge dark scars visible on Jupiter for months afterward the comet impact were a powerful reminder of the energy out there in space and the threat that hovers out there. The other thing our observations of space impacts have taught us, apart from their immense power, is that there will always be another one some day on all planets and moons - and we are no exception. However while we dwell on this unnerving this thought, we also face the brighter prospect that space rocks can be great source of resources for our civilisation. Already there are companies investing in space hardware hoping to lead us to landing and mining on asteroids. The prospects are good; some meteorites found on Earth have been found to almost solid platinum, for example, and there is no reason not suppose that some asteroids will be very rich in materials indeed. Even if they are nothing but ancient rock and dust Nasa is already developing equipment to synthesize building materials from lunar regolith and machines that can use this cosmic concrete and turn it into structures.
The holy grail for harvesting materials in space is, of course, water, now known to be present as ice on Mars and the Moon, but not only for human survival - water is hydrogen and oxygen, the two components of liquid rocket fuel. So find a simple way to split the two in situ and ice will supply both drinking water and juice of a different kind. Crucially it will make any duly equipped space mission somewhat self sufficient, and hopefully bring down the cost greatly for manned missions. Currently we are still stuck in the early stages and the main reason is the money it takes to transport people any distance in space. Bring the cost down and all the benefits of human exploration can come to the fore.
While it is true that the Apollo moon landings were hugely expensive their crews did get an enormous amount of work done in the few days they were on the surface. They may not need food and oxygen and a host of supplies bringing along but even the most advanced of robot space probes still cannot compete with a human in a space suit when it comes to exploration. Humans on the moon managed to deploy experiments, dig the soil, take photographs, and perhaps most importantly, come back and tell us what it was like to experience the moon Earthrises and an Earth eclipse (The vista of the moon was "Magnificent desolation" in the words of Buzz Aldrin). Plus the lunar rover taken on later missions did not have to be remote controlled; the astronauts could drive it just like a go kart. If a manned Martian mission had a rover then removing the long delay in transmission signals would make exploration much more straightforward. And if the vehicle developed a fault, human hands are still unmatched in being able to fix things. Putting people in space is dangerous of course, but getting them safely there may help mitigate some of inherent risks by calling on the ingenuity of the astronauts called up to the task. The Apollo 13 crew still provide the prime example of the drawbacks and strengths of travelling into the solar system in spacecraft. A small minor fault nearly killed the crew... but only nearly. The crews training and calm heads, and the work of controllers back on Earth brought them back again in one piece.
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The Sun
The last destination in the solar system that we have not visited is the most important of all, and the one we really won't be visiting at all. Ever. Our own star dominates our lives and that of the planet so completely that grasping the full enormity of what is going on is almost impossible to fathom. As the sci fi author and comedy writer Douglas Adams put it, when considering the how much we take our cosmic circumstances for granted;
"The fact that we live at the bottom of a deep gravity well, on the surface of a gas covered planet going around a nuclear fireball 90 million miles away and think this to be normal is obviously some indication of how skewed our perspective tends to be."
Of course this perspective comes from being mostly bound to the surface of our planet and only able to see at best a few kilometres into the distance, so of seems as though the sun is going around us. The days, nights and seasons are so ingrained in our DNA that we never consider the mechanisms and physics involved. Only on very rare occasions does something interrupt our routine.
The most dramatic event that highlights the nature of our status as inhabitants of a planet flying around a star is the total eclipse. By complete coincidence our moon is exactly the right size and distance from us to completely blot out the sun on the occasions when it passes in front. This is an entirely routine and predictable event, but since the shadow of the moon only falls on small corridors of land during an eclipse, and cloud cover can easily hide the spectacle, many people live a lifetime without seeing a total solar eclipse and the three unique sights of the event. Firstly, the daytime sunlight fades away for two or three minutes before returning, in such a complete way that even partial eclipses don't approach; secondly the horizon sky turns orange in sunset, but a 360 degree sunset in every direction; thirdly is the most stunning sight of all; the sun's atmosphere, it's corona, normally impossible to see next to the light of the sun, with the moons help the white streams of radiation stand out clearly against the blackness of the sky.
Since the sun is bright enough to leave an image of itself on our retinas for minutes even with the briefest of glances from xx million miles away it is hard to imagine how it is possible to make any observations of it or to understand how it works. Naturally though, we have, and understanding does not begin purely with the space age but back centuries. Ingenious inventors were figuring out how to observe the sun with blacked out screens, mirrors and projections for centuries, meaning that the first drawings of sun spots - the large sunken darkened patches in the sun's outer surface caused by transient magnetic effects - long predate telescopes. On fact they date back to ancient times, even before many religions and influential but incorrect thinkers like Aristotle were suggesting the sun had a divine perfection and lack of obvious flaws. Lots of observers credited the large black dots on the surface to passing planets; another incorrect supposition disproved by the telescope in the 17th century. Galileo among his other observations demonstrated they were surface features.
The discovery of infra red and ultra violet wavelengths beyond the visible spectrum of light really opened up the study of the sun and its atmosphere. Today many images of the sun we see are from IR and UV cameras which block out much of the dazzling visible light photons our eyes see (or rather see for moments before we avert our eyes) and only record those specific wavelengths. Cameras were trained on the sun remarkably quickly - no sooner was photography invented than the sun was successfully imaged in 1845. Only six years later a total eclipse was recorded for the first time, and things progressed ever since. Though we cannot get anywhere near it through observation, extrapolation and experimentation here on Earth we now know huge amounts about the sun and the other stars too. We know the sun burns to colour it does because of its temperature and we also know all other stars share the same components as ours does; mostly hydrogen and helium. We know we are witnessing a giant nuclear fusion reactor in our sky, as the immense pressures and gravity fuse hydrogen into.helium. Though the sun consists of 99 percent of the mass of the solar system it seemed impossible before the 20th century discovery of.nuclear physics that it could have burned for millions of years without burning out.
Fusion does not happen often - it's a one in 5 billion year chance for each atom, but because there are so many atoms in the sun's core enough fusion is still happening to generate heat. Amazingly by volume the suns core generates less energy than the equivalent sized humans metabolism does, it's just that the suns core is 25 times times the size of Earth that makes it so powerful overall. The sheer rarity of natural fusion reactions keeps it very stable. Most of the time nearly all the matter in the sun's core is not fusing, luckily for us because if fusion happened more often the sun would have burnt out already. As it is the very slightly release of energy and loss of hydrogen into helium makes the sun glow gradually brighter by about 1% every 100 million years or so. Because of the great density can be a million years for the photons created in the sun's core to reach the surface. Gravity is not the only barrier to energy escaping the sun. There is (we think) a huge electrically charged plasma layer above the sun's core, a massive irradiated zone and an outer layer of huge convection currents. The convection layer is more good for news us as the photons are greatly cooled and removed of energy in this area. If it was not there the sun would radiate X rays rather than visible light and life would not be possible on any planet in the Solar system.
The energy that reaches us on Earth is but a fraction of the so called solar wind that radiates out from the star. We have known about the solar wind since the mid 19th century. Back then it was widely assumed to be travelling through some kind of invisible medium.- the luminiferous aether as it was often called - before 20th century physicists proved that the sun's energy travels as waves through the emptiness of.space. The huge aurorae, commonly called the Northern lights, were correctly hypothesised to.be caused by the sun's influence, and demonstrate what a debt we owe our atmosphere and magnetosphere - without it all the matter that causes the huge light show in the upper atmosphere would be hitting us. In the 1970s the Skylab space station was able.to photograph the sun in extraordinary detail through its Apollo telescope, a space borne precursor of the Hubble telescope, except that Hubble cannot be angled near the sun or it's optics would be destroyed.
Skylab's telescope was designed specially for solar observation. It's most famous images were of huge tongues of fire leaping from from the sun far out from the surface, far beyond what had been considered likely given the relatively stable nature of.the sun. After years of study we know now that the solar flares are caused by the same magnetism as sunspots. Unlike a solid planet like earth.with a stable magnetic field the sun is fluid gas and it as it rotates it mixes up its magnetic field into a turbulent seething mess. Every so often two separate areas of magnetic charge join together and energy leaps between the two points, creating the flare. These solar flares are now closely monitored from Earth as the mass ejection of charged particles they send our way have the power to disrupt satellites, electricity grids and certainly the harm any humans in space.
The first space probe to be placed in orbit near the sun was the European Space Agency's Ulysses craft. In doing so the scientists were able to record the magnetic activity at all latitudes on the surface and measure the solar wind for the first time in space. The furthest recording of the solar wind came from Voyager 1 in 2012 as it recorded the last tiny wisps of solar particles and recorded a large upswing in high energy particles thought to originate in supernovae. The 'heliosheath' or end of the solar wind, the surface of the suns magnetic bubble, is considered the edge of interstellar space and Voyager 1 became the first physical evidence of our existence in the wider universe. The Solar system itself, when defined as objects orbiting the the sun, continues on for at least seven times the distance as the heliopause. And the sun's gravitational influence reaches further still. It will take the Voyagers, pioneers and new horizons thousands of years to exceed that milestone. In about 250 million years they will complete an orbit of our milky way galaxy. In.5 to.6 billion years, when the sun finally runs out of fuel.and expands into a red giant, swallowing mercury, Venus, the Earth and moon, the space probes should still be out there somewhere, carrying images and sounds of Earth on the Pioneer plaques and Voyager gold discs, and the remains of an eminent scientist on New Horizons, snapshots of their time, representing the billions of people who were born before and after the craft left.
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Touchdown
Less tangible evidence of humanity has been broadcasting out into space now for over two hundred years. The earliest human transmissions, the first crude experimental blasts of electromagnetic radiation created by scientists toying with electricity and magnetism in the early 19th century, at about the same time the first steam railways were being built, have spread out, like.ripples in a pond, around 200 light years so far. Putting ourselves in the shoes of a theoretical alien race watching us from a few light years away we could have flown by the Earth in our flying saucers a few centuries ago and detected nothing on our radio receivers. The first radio broadcasts will have made it around 110 light years. Television programmes still less than 100 light years. It sounds a long way, and by spacecraft standard s it is - Voyager 1 is 18 light hours, not years, away and needs another 17 thousand years to go one light year. But on a galactic scale it's nothing. We reckon that the milky way is about.100,000 plus light years across. Meaning that at Voyager speed it can be crossed in about 1.7 billion years. Though it seems as if our deep Space probes are distant lonely emissaries unimaginably far from home, in galactic terms they are really just down the road. Carl Sagan was not exaggerating when he called the Earth a "lonely speck in the great enveloping cosmic dark" on seeing Voyager 1's view of Earth as a tiny dot from Neptune.
Though we tend to think of radio as a strange intangible broadcasting medium it is in fact just another electromagnetic wave, albeit with very long wavelengths- hence it's use for communication. Radio telescopes were one of the first kind of telescopes built on Earth to detect waves beyond the visible. Since radio easily penetrates Earths atmosphere a large dish and focusing mirrors can collect radio waves relatively easily. Many of the most famous astronomy landmarks of Earth are radio telescope receivers; Jodrell Bank in Cheshire England was the first really big movable radio telescope in the 1950s; the massive Arecibo dish in Puerto Rico, recessed into a mountainous depression in the hills is a movie star, having taken a role in a James Bond film, Contact and the X Files. Arecibo has the strongest radio beacon on the Earth, so if aliens do chance upon any radio broadcasts, it could be coming from this huge dish.
After seeing all that the solar system has to offer it is finally worth considering all that has happened on the Earth. The place has changed a huge amount, should anyone - or thing - be watching, they would be struck by the changes. If our theoretical alien visitors from the 18th century have come back recently they would be hearing a cacophony of electromagnetic radiation from all over the planet, from every mobile phone and WiFi connection, every television and radio, every aeroplane and car. looking back at this curious planet we can see whole swathes of it lit up by artificial lights when it rotates away from it's sun. And there are thousands of tiny satellites zipping around the planet, broadcasting their own signals to us.
The Earth has become a very different place in the last two centuries. In the 19th century the planet was suddenly covered in factories and steam engines, wrapped up with telegraph wires and railways, bringing the modern age of mass communication and shrinking distances between cities and countries, but that was just the start of things. In the 21st century the Earth is now dotted.with observatories and circled by orbiting data gatherers collecting light all across the spectrum; visible and, non visible, from the very low wavelength radio the very high wavelength x rays.and gamma rays. The last two are especially hard to collect as they pass straight through most things, including our own bodies (thus creating the x ray photographs of our innards in hospitals) and the reflecting mirrors that allow other telescopes to focus light. Most wavelengths above radio are disrupted by the atmosphere, hence the many orbiting observatories, most famously the Hubble and now it's successor under construction, the James Webb telescope, planned to sit twice as far as Hubble. Equipped.with greatly enchanced infra red capabilities. The JMST will be able both to look much further than Hubble and has much better shielding from interference from nearby light and heat sources like the Earth, sun and its home planet.
When it comes to scanning the heavens, the detection of microwaves has been one of the most exciting areas of study ever since the discovery of the cosmic background radiation in the 1960s. These stupendously ancient microwave traces are thought to be remnants of the Big Bang itself, and the European Space Agency's Planck orbiter is the current microwave detector du jour, its mission to examine the radiation and hopefully provide enough data to give cosmologists a clue to the very nature of the creation of the universe itself. But you don't need to be in space to get a better view. Nasa have an infrared telescope mounted aboard a Boeing 747, the SOFIA, (Stratospheric Observatory for Infra Red Astronomy) cruising well above much of the atmosphere and it's blocking effects on UV light. The aircraft has an advantage on ground telescopes in that it can fly to.any latitude and see the northern and southern night skies. The downside is that a lot of computer controlled active mounting points are needed to compensate for the motion of the telescopes host plane as it bumps around the sky. Aircraft telescopes have made some breakthroughs to call their own; in the 1970s Nasas first airborne observatory (also called the Kuiper as with the Kuiper belts) was the first telescope to see the rings of Uranus.
Dry, high altitude air is the reason for some of the most famous telescope locations. High in the Chilean Andes in the Atacama desert, two thirds of the way up to the height of cruising airliners are two major locations - the Llano de Chajantor, and Atacama Cosmology Telescope. Llano de Chajantor is home to the billion dollar ALMA; the Millimetre and Submillimetre array, which, as the name suggests, can detect radiation at wavelengths below a millimetre long from some of the least active parts of the cosmos. It's detectors are spread.out over many square miles making the largest single.location telescope in the world. Those working at the Atacama sites face tough living conditions because of the remoteness of the location and the high altitude. The insides of.the buildings on the Atacama have to be supplied with extra oxygen, as do the vehicles that drive the Cerro Chajantor pass, a rough unsurfaced road providing the only link to civilisation. The observatories are not.the only link with outer space on the dry, empty desert. Ever since the Apollo age, Space agencies have come to chile to test both their equipment and astronauts in one of the most alien landscapes it is possible.to find on Earth.
The world's most famous operational observatory is probably the one atop Mauna Kea in Hawaii, another very dry and high place, albeit in a more accessible location than the Chilean mountains. The twin domes of the huge Keck Telescopes, with their 10 metre mirrors are the most distinctive. The mirrors are actually segmented in 36 pieces, all computer controlled to within nanometer tolerances - all designed to counteract the interfering effects of the atmosphere and gravity. Though located in an American state many of the telescopes are international concerns. The cylindrical Japanese Subaru telescope, looking like a big cake tin, stands next to the Keck buildings. Across on the other side of the summit is the Franco Canadian telescope, the international Gemini telescope and the Univeristy of Hawaii's own facility, the oldest on the summit. The biggest American observatory is the Very large array In the empty centre of New Mexico - the same expanse of wilderness.that bore witness to the first atomic explosion thirty years before the VLAs first telescope was switched on. Another highly photogenic site, the 27 radio receiving dishes lined up in a Y shape pattern on a barren plain backed by distant mountains, were a critical part of the Voyager missions, receiving the signals from Uranus and Neptune. All the identical dishes are mounted on railway tracks and can be moved around into many patterns depending on the intended target being observed.
In the more developed areas of Earth the hundreds of unseen satellites zooming around above our heads have revolutionised life down on the ground, giving us all a global positioning system that can tell anybody almost exactly where they are standing, and consequently provide satellite navigation, and global communication. Using the network of satellites any one point on the Earth can talk with any other point, bypassing the need for the telegraph cables and radio masts of previous generations. In theory radio masts could have circled the globe but politics would have put a stop to it; never could the United States, for example, have strung a network of radio towers across, say, the Soviet Union and China. Being able to blast a satellite into the Earth's orbit bypassed all of that and brought instant (or nearly instant) television and radio broadcasts around the world. It's all taken for granted these days
At the dawn of the space age the Soviet Union built the vast sprawling Baikonur Cosmodrome on the deserted steppes of Kazakhstan. Appropriately for the place that sent the first manned rockets into space, it already looked like it was an alien world - vast open space, little signs of life among the dusty rocks and far off mountains. Ironically there was once a time when NASA probably knew more about the moon than the operations at Baikonur, or what went on at Star City, the cosmonaut training base on the outskirts of Moscow. For twenty years or so the best the west could do before the Soviet press releases came out was aim a telescope like Jodrell Bank's big dish at the Russian missions radio signals and track what they were doing. Aside from the availability of information coming out of Russia, little has changed as the time passes. The place looks much the same today as it did in the 1960s, with the passage of time marked in the mysterious remains of abandoned launchpads, some looking as though they have suffered huge explosions, with the remains of structures betraying that they were removed not by careful dismantling but by a blast wave. The scene of the first manned rocket launches into space still stands, and still launches the Soyuz craft towards the International Space Station.
All around though are the abandoned ruins of the glory days that the coffers can no longer sustain, most notably the huge double launchpad built to take a Soviet spaceship to the moon, and later modified to launch the Russian space shuttle. That Shuttle sat mothballed in a giant hangar for a decade and a half, before being destroyed when the hangar's roof caved in, flattening everything underneath and killing six people inside. One day all activity may cease and the Cosmodrome may vanish entirely. In Vladimir Putin's Russia it is being supplemented by a new centre closer to the powerbase in Moscow than a the steppes of a now-foreign neighbour nation. For now the main road through the low buildings to the pad - 'The Road to The Stars' as it translates into English - is still there, commemorating a brief but glory-filled time. The age of Soviet manned flights soaring above the rest of the world lasted for eight missions and four years - six Vostoks, launching five men and one woman, and two Voskhods with five more - but it was never quite as easy as it seemed, even when it seemed as though Russia could do no wrong. The cosmonauts would be suited up, ride in a bus to the foot of the pad, receiving plaudits for the cameras, before waving in patriotic salute, before riding the the elevator the top, where they would strap in and wait to fly into the great void.
It was never quite as easy as it seemed, even when it seemed as though Russia could do no wrong. The Cosmodrome is the scene of the worst disaster by far in the space industry. In 1960 an R16 booster second stage fired prematurely on the launch pad, blowing up the fully fuelled first stage underneath. Over one hundred launchpad workers were killed, and the calamity was kept secret for decade. For the cosmonauts themselves it paid to not think too much about their situation while waiting for liftoff. For all the furious activity around them they had a serene quiet space to wait. Claustrophobia was not an option, but at least the earliest spacemen and woman had an ejector seat. When the Soviets wanted to put more men inside Vostok they took out the ejector seats and pressure suits and packed them in like sardines. When all went well those who came back in one piece found themselves becoming walking propaganda tools, finding themselves frustrated by officialdom keen to keep the people's heroes safe from harm, and very few of those pioneers made it back from their first landing site to a second launch despite their great willingness to go and clear suitability for the job.
Florida's Cape Canaveral is still the home of NASA's launches, and grew out of a post war testing base at a Naval Air Station where the Americans tested their first rockets in the early 1950s. Being on the edge of a great stretch of low-lying, flat and straight coastline, the area was the natural progression when those rockets became large enough to fly into space. Over the course of the 1950s and 1960s the stretch of coastline was dotted with tens of different launchpads though very little of them has survived their brief operational lives. Canaveral, like it's Russian counterpart is scattered with abandoned launchpads, the disused remnants of their own 1960s golden age, when NASA was handed money by it's government in a way they never would be again. Each one tells a story; Al Shepard and Gus Grissom took their pioneering suborbital Mercury flights atop their Redstone missiles from a football pitch sized square of concrete a little ways in from the shore. The Redstone was tiny compared to later efforts - The Atlas and Titan - and the later Mercury space capsules took flight to space from a row of launch pads a few miles further north. More powerful rockets needed more equipment and people to run, so 'blockhouses' - strengthened control bunkers - were built at each pad. The launch gantries were built by oil rig manufacturers, the best people for the job of building great scaffoldings of metal. The end result looking like a cross between the great skyscrapers of Manhattan and Chicago, and the oil derricks of Texas and California.
The ever changing layout and many abandoned launch sites at the Cape testifies to the speed of the space race, the great power increases and also the greater power of computers. The Redstone launch looks a little like a scaled-up hobbyists effort; fast forward only a couple of years and the launch pads were much larger, with great moving support towers on railway tracks looming over deep flame pits. Impressive as these sites were, they were nothing like the scale needed for the Saturn V moon rocket, so they too were left to the weeds. Their replacements, the world famous Pads 39A and 39B, where the Apollo moon missions were launched, and where the Space Shuttle would launch from, were built further north up the Cape, and are still in use today. Some places quietly reflect the sadder stories; the only sign of Launch Pad 34 where the ill-fated Apollo 1 crew perished in a fire aboard their capsule during a launch rehearsal are the large concrete bases, with a small memorial to the three crew in their shadow. The great gantry above long since removed. As if recognising the lack of landmarks NASA has built gardens out of unused rockets, stands of silent obsolete machinery, sitting in groves like the arboretums of European stately homes. Not all has been left to history and nature, some of the launch sites are still in use for unmanned mission, the pad where the two Voyager spacecraft set out for interstellar space, and the Mariner missions to Mars and Venus began their flights is still there in regular use.
In the earliest days of the US space programme everything was kept in-house at "The Cape". The Mercury missions were controlled from a mission control room near their launchpad, but with the coming of the much more complicated Gemini and Apollo plans the government outsourced the flight control, astronaut training, and management facilities elsewhere where all the buildings could be made as large as they pleased. Opened in 1963 Houston Mission Control has become so synonymous with the moon landings and the Shuttle missions that it is easy to forget that it is hundred of miles from Florida in Texas. All that can be seen from the windows of the Lyndon B Johnson Space Center is some fields, trees and a lake. Aside from the signs the main giveaway to the purpose of the quiet collection of mid-20th century concrete modernist buildings is the spare Saturn V rocket laid on it's side at the entrance. Visually most of the many NASA setups across the country are a long way from dreams of schoolchildren on the outside, but great things are still happening on the inside.
Cape Canaveral and Houston are the areas inextricably linked, but California has been just as historically important to Nasa. As well as having it's own, albeit much smaller launch site on the Pacific coast at Vandenburg Air Force Base (once intended for Space Shuttle launches until the Challenger disaster scuppered the idea), it was where most of their storied manned spacecraft were built. In the Downey neighborhood of Los Angeles once stood the Rockwell works where the Apollo CSM, the Space Shuttles, and Skylab were all built during the 1960s and 70s. The factory that produced some of the most significant and famous machines in history closed in 1999, and partly demolished. Downey's main claim to fame is now a film studio that took over some of the old aerospace factory. The Voyagers may have been launched from the east coast of the United States, but they were controlled from a building thousands of miles away in the northern outskirts of greater Los Angeles. That NASA's Jet Propulsion Laboratory, the nerve centre for most of the great unmanned missions - Mariner, Viking, Voyager, Galileo, Cassini, et al - sits on the other side of the continent from the spacecraft launch centre shows how much the business of flying into space has become a global enterprise, with important outposts dotted all around the world in a huge network. The process that began with radio receivers in military tracking stations being used to follow the path of the orbiting space capsules now encompasses hundreds of thousands of computers all networked together in countless rooms in cities on every continent, (including Antarctica).
Now, the space probes are on the lookout for planets in solar systems around other suns. Exo-planets, as they are called, and already telescopes such as the Kepler , (named, of course, for Johannes Kepler, the man who codified the motion of solar systems), by analysing the gravitational changes (or "wobble" as it is often more descriptively put) caused by orbiting planets, and the minute differences in light detected when a planet passes in front of it's home star, have discovered evidence of hundreds, including ones sat in a similar location near to their star as we find ourselves. Of course the inhospitable environments of Venus and Mars show that life isn't a given even in very familiar surroundings, and thinking life could be another matter. We are the only ones of the millions of species on our own planet who can think to any deep level, and even that seems like an accident of history. The time factor easily forgotten too - science fiction usually presents us and all our alien friends all living at the same time, something that seems quite unlikely. Still, such is the human need to explore, and our ingenuity in building machines and technology to do our exploring with, that we never seem to let our lonely position in the midst of a great deal of nothing put us off. At the time of writing this there has even been the discovery of another solar system with eight planets, albeit much more compact than ours. These days, the next big thing is never too far away, whether or not we will feel the need to take ourselves back out there any time soon.
