Imagine the Earth in the future. Are there flying cars, floating cities, outposts scattered across the ocean floors, and artificially intelligent cyborgs? This is the magical, technologically advanced world that science fiction paints. But is it realistic? By 2050, the UN predicts that Earth’s human population will have grown from 7.1 billion to between 8.3 and 10.9 billion and may only continue to grow. In this version of the future, many questions will surround the sustainability of world populations, the growing pressures on the environment, global food supplies and energy resources. Will the Earth be able to sustain us? With the answer to this question unknown but worrying nonetheless, humanity needs to start planning for the future and to contemplate leaving the safety net of the Earth and looking towards the stars. Stephen Hawking has stated that the colonisation of space would be the best way to ensure the survival of humanity. Although I believe there are other ways to ensure our species lives on, space settlement is the next logical step after space exploration – it implies the permanent or long-term presence of humans in an environment outside Earth. But if we leave our home, suddenly we will be living outside of what we consider to be ‘normal’ and will be attempting to inhabit environments in which we are not originally biologically designed to survive. We will have to become the extremophiles, a generation of aliens and Life 2.0.
Why and Where Should We Go?
When in 1961 Russian cosmonaut Yuri Gagarin was blasted into orbit and safely returned, he became the first man in space and people were finally given substantial evidence to support the idea that humans could travel off-world. Subsequently, and since the year 2000, humanity has been continuously living in space. Although a colony of fewer than 10 people, the International Space Station is our first extraterrestrial outpost, an inhabited satellite orbiting the Earth. No terrestrial or land-based space colonies have been built thus far, yet this is the dream as investigating the habitability of other worlds not only benefits our understanding of the versatility of life, it also takes us closer to answering one of humanity’s oldest questions – are we alone? Our permanent residence in space is helping us prepare for a future when humans may need to be able to live and work on other planets and moons.
In the long term, i.e. another 3 billion years, our Sun will start to expand and enter its red-giant phase as it draws closer to its death. It will engulf Venus, and even if it doesn’t swell enough to reach the Earth, it will still boil off the oceans and heat the surface to temperatures that even the hardiest extremophile could not survive. This, however, is a rather long way off and not really a good enough reason to start the process of moving right now. So why would we want an off-world colony today? Or more importantly, why should we want one. There is no denying that it would be magnificent to have people living on multiple worlds, nor that sadly the Earth is beginning to sag under the pressure of humanity. We are on the verge of self-inflicted destruction, whereby the damage we are doing to our planet is progressing faster than our capabilities to fix it. Off-world colonies could, and I strongly emphasise could, improve the chances of human civilisation surviving in the event that the Earth becomes uninhabitable. Life is fragile and any number of natural or man-made catastrophes could occur, such as another Snowball Earth, asteroid impact, nuclear war or complete depletion of our natural resources. This paints a very bleak and somewhat depressing picture of our future. Hopefully long before any of these scenarios come to pass, I believe we will choose to leave Earth for the purpose of exploration and scientific enlightenment, because it is built into us to want to travel and unravel the mysteries beyond our physical and intellectual borders. If we happen to set up humanity’s lifeboat in the process, then even better.
As such we need to explore how humans might be able to live and work on other planets, moons and in space itself, as one day that need may become an imperative and that imperative a reality. What might it be like to live on other worlds in our Solar System? A great thought experiment with a similar theme and plot-line to the film Interstellar, assumes that we have developed the capability to skip across the Solar System to its farthest reaches and have the knowledge and technology needed to build a human outpost on any world of our choosing in the Solar System. Where would it be?
Mercury
Starting from the inside out, humanity could move to Mercury – and it goes without saying, its surface would be an extremely inhospitable place in which to land unprotected. It would not be our first choice, that’s for sure! Like the Moon, it lacks a protective atmosphere, so colonists and their equipment would need thermal protection from the intense heat of the Sun, and require shielding from the powerful solar radiation that reaches the surface and infrared radiation of any very hot region of Mercury’s crust. Because of its rocky, barren and airless similarities with the Moon, any settlement of Mercury might be performed using the same general technology, approach and equipment as a colonisation attempt on the Moon. Unlike the Moon, however, Mercury has the advantage of a magnetic field that protects it from cosmic rays and solar flares, and a larger surface gravity of about 0.37g, almost exactly equal to that of Mars – just over one-third of the gravity on Earth. This means that heavy equipment and building materials would be easier to lift and move around and, as an amusing bonus, a human could jump three times as high. Due to its proximity to the Sun, the surface of Mercury can reach 427°C (800°F) near the equator during the day (hot enough to melt lead) and fall to –180°C (–292°F) at night, with temperatures at the poles being even colder – that’s a lot for the human body to deal with. For a planet located so close to the Sun, it is perhaps surprising that significant deposits of ice lie hidden in the shadows of polar impact craters. Could this ice be mined to access water on Mercury? These polar regions could actually be a good spot for settlements, providing a source of water and a break from the intense heat of the Sun. Weirdly, a colony would not really have to worry about any natural disasters wiping them out as, without an atmosphere, Mercury has no weather and with no bodies of liquid water or active volcanoes, there is very little risk of devastating tsunamis or volcanic eruptions. Interestingly, this lack of atmosphere would mean that during the day, the sky would appear black, not blue – that would just be odd! Sadly, like all planetary bodies in the Solar System, however, there is always the threat of asteroid impacts and, potentially, earthquakes (Merquakes?!), owing to compressive forces that shrink and squash the planet. Happily, it only takes around five minutes for signals to bounce between Mercury and Earth, so there could be a stunted but very achievable conversation with home. Who would have thought that Mercury would actually be quite an attractive option?
Venus
Next for consideration is Venus, our Solar System’s equivalent to the mythical realm of Hell. Already it sounds appealing, doesn’t it? Without technological help (which is far beyond our capabilities at the present time), our fragile human bodies would die in less than 10 seconds on the surface, instantly crushed while being simultaneously cremated. The last, very quick, breath taken would be of toxic gas. Life on Venus would be nauseating, brutal and very short. If we could somehow surmount these issues, then the best place to set up camp would be somewhere on the flat, smooth plains that can be found on more than two-thirds of the planet. Walking around would not be a pleasant experience with surface temperatures of 465°C (869°F), and air so thick that every step would be like trying to run in water. The planet’s gravity would not be a problem, however, as it is almost 91 per cent of that of Earth so would probably not feel much different, but the atmospheric pressure is 92 bars – tantamount to living more than 900m (3,000ft) beneath the ocean on Earth.
High in the atmosphere on Venus, winds travel up to 400kph (249mph) – faster than any tornado or hurricane witnessed on Earth – interspersed with fierce bursts of lightning that, as a small mercy, never reach the already challenging surface. The roasting heat prevents any rain from touching ground so water is never able to collect or even wet the surface. The active volcanoes on Venus may add yet another danger to colonists as the eruptions are thought to be so large that they could re-surface the whole planet. It would take only a few minutes to get a distress call home when the planets are closest, but when Venus disappears to the other side of the Sun it would take up to 15 minutes. Not that any help would be close at hand should it be needed, nor could anyone really offer assistance against such an inhospitable surface environment.
The type of habitat that could use the strengths of Venus’ extreme conditions is one filled with gases of the same composition as Earth’s atmosphere at sea level (so colonists could breathe) but floating high in the dense Venusian atmosphere. The atmospheric pressure at 50km (31 miles) above the surface of Venus is similar to that on Earth at sea level (1 bar), and temperatures are just over 0°C (32°F) at that altitude. Just like a weather balloon, a floating habitat with internal pressure like that on Earth would rise to an altitude on Venus where the external pressure was the same. If this were actually possible, a human could walk outside on to a ramp using just an oxygen tank and look out over the Venusian clouds below. The habitats would produce their own oxygen through photosynthesising vegetation, which would not be difficult to grow in Venus’s carbon dioxide-rich atmosphere, and water could be extracted from the sulphuric acid in the clouds. Theoretically, anything is possible.
The Asteroid Belt
Although perhaps a surprising choice, there is a real option of moving to a dwarf planet such as Ceres, the largest object in the Asteroid Belt. The objects of this orbiting rock garden have been suggested as potential sites for future space-mining operations hoping to reap water for its hydrogen to make rocket fuel; oxygen to provide breathable air to make long-distance space missions possible; and ore minerals. They are also seen as potential staging posts and transport hubs for deeper space exploration due to their lower escape velocity. The main fear any colonists would have living on these objects would be of one asteroid bumping into another, and the resulting threat of knocking objects out of the belt and on to a collision course with Earth.
Comprising one-third of the mass of the entire asteroid belt, Ceres could quite possibly become the main asteroid base for future trips to Mars, as it is not a dead lump of pockmarked rock, as commonly comes to mind when we think of an asteroid. Ceres may actually contain more water ice buried beneath its surface than all the fresh water flowing across the Earth, and although its gravity is less than 3 per cent that of the Earth, it is one of the most suitable locations for a permanent human base. Ceres is currently not believed to have a magnetic field so its surface is not shielded from cosmic rays or other forms of radiation, and it does not have a significant atmosphere, so there is no weather (adverse or otherwise) and it always remains well below freezing. NASA’s Dawn spacecraft was the first to visit Ceres, having arrived in orbit in March 2015, and was greeted by a complex and beautiful landscape full of weird-shaped craters, a 6.5km- (4-mile-) high mountain, mysterious bright spots that might be huge deposits of salt, and an entirely dry surface. Excitingly for life, however, there may be liquid water inside the dwarf world as water vapour has been seen erupting from it into space, possibly from volcano-like icy geysers. Thankfully, these vapour jets would be far too weak to pose any danger to humans but they hint at the world’s potential to support life. The relatively small size of Ceres is a selling point as well. Hiking across its surface to find a suitable site to live would not take very long (relative to travelling around a planet or moon that is) – Ceres has a diameter of 950km (590 miles), just short of the distance from the south coast of England to the north of Scotland.
Europa
Despite depictions within some entertaining science-fiction films, humanity could not even contemplate living on Jupiter. A purely gaseous world, there is probably no solid surface on which a crew might touch down, which makes colonisation impossible – unless you fancy setting foot directly on to its core and can tackle the crushing weight of liquid hydrogen bearing down on you. We might be able to live in orbit around Jupiter, however, and harvest its energy to provide the resources for colonisation of any number of its 60 nearby moons. If you ask an astrobiologist they will instantly suggest setting up a base on Europa due to the tantalising idea that life may already live beneath its icy shell. In reality, Callisto with its own large amounts of water ice, low radiation levels and relative geological stability would be ideal. However, where is the adventure in that? For human explorers setting up a research base on Europa, the cold, icy surface would actually be quite suitable. It is relatively flat and, although crisscrossed with small ridges, these are little more than a few metres high so should not prevent construction nor journeys across the landscape. A serious threat to life, however, is Jupiter’s magnetosphere, which bombards Europa with deadly radiation. The best location for a base would therefore be either protected below Europa’s icy crust or on the hemisphere of the moon that faces away from Jupiter, as this receives the least amount of radiation. Like our Moon, gravity is low (about 13 per cent that of the Earth), so going for a walk on either moon would be a similar experience, and also means that both have an almost imaginary weatherless atmosphere. Colonists, if daring to live on Europa’s surface in inflatable igloos, would need them heated to help deal with the blistering cold outside (down to –220°C/–364°F at the poles), reinforced to withstand icequakes, and located away from possible powerful plumes of water shooting out through the icy surface from layers far beneath. If you wanted to email research findings home, a message would take at least 30 minutes to arrive, and only when the gargantuan bulk of Jupiter wasn’t blocking the way. Oh, and don’t even think about making a voice call.
Enceladus and Titan
For the same reasons as Jupiter, Saturn is not a place where you want to end up. However, if you had to make an emergency landing somewhere in this system and could make it to Titan, then you might have a chance of survival as you could jump out of your ship without the need for a pressurised spacesuit – you’d simply need a tank of oxygen and some insulating clothing. With its thick atmosphere, standing on the surface of Titan would feel rather like being submerged in a swimming pool on Earth. The landscape also resembles that of the Earth and there is a number of flat areas of land for a colony to build upon. If this weren’t enough good news, Titan is primarily composed of water ice and rocky material and NASA’s Cassini mission showed exciting hints of an ocean inside it, which might be as salty as the Earth’s Dead Sea. Colonists would just need to melt this surface ice, and/or access the ocean and filter out the salt. One downside is that although the surface is covered in aqueous bodies, humans could not drink the hydrocarbon-rich liquid – it would be like trying to drink tar. Excitingly, Titan offers a lot to work with, as it already possesses an abundance of all the elements necessary to support life. Water can easily be used to generate oxygen and nitrogen to add to breathable air. Nitrogen, methane and ammonia can all be used to produce fertiliser for growing food. The best thing about Titan concerns transportation, which takes on a whole new dimension because of the moon’s low gravity (more or less 14 per cent that of Earth) and dense atmosphere – colonists could strap on wings and fly! It has weather in the form of methane rain and thunderstorms but no cyclones or tornadoes, and its atmosphere would protect colonists from cosmic rays and many incoming projectiles. In addition, there are no moonquakes as far as is known and the existence of cryovolcanoes is still debated – it is a pretty comfortable, safe and quite possibly enjoyable place in which to live. It gets my vote!
If a spacecraft carrying colonists ended up on Enceladus, one of Saturn’s other moons, then life would be a lot harder. The main dangers here are the freezing cold temperatures, minimal air pressure and explosive geysers. Due to the moon’s icy surface, most of the sunlight it receives is reflected back into space, lowering the temperature to an average –201°C (–330°F) throughout the day. As a result of its sparse atmosphere, it has no extreme weather for colonists to worry about, but is left exposed to incoming space debris and radiation. The best locations for a human base would be near to the tiger stripes in the southern polar region as these would provide a source of heat and power. These giant fissures spew plumes of frozen ice particles and cold vapour into space, thereby producing nearly 16 gigawatts of power – a reasonable trade-off for the danger of living close by. The source of this power is believed to be the ocean lurking beneath the ice, which may also harbour indigenous life forms. The moon’s tiny gravity, just 1 per cent that of the Earth, would hamper travelling around. It is not really a world you want to end up on forever.
Uranus and Neptune
Once we get to this frigid neck of the Solar System, colonisation is much more possible on moons than planets. This is because, just as with Jupiter and Saturn, Uranus and Neptune lack much in the way of a solid surface under their layers of ice and gas on which to settle. The pressures below the thick atmosphere on Uranus are enormous and would instantaneously crush any life form. Also, there is no process inside Uranus, such as volcanism on Earth, that would give colonists a form of energy to use as a replacement for the very distant Sun. Out of the 27 moons orbiting Uranus, two prime targets for colonisation would be Titania and Miranda. Not a huge amount is known yet about these moons, but it is thought that they have a solid surface on which a mission could at least attempt to touch down. All of Uranus’s moons lack weather systems and surface pressure due to non-existent atmospheres, and it is probably a safe assumption to say there is a multitude of as yet unknown hazards waiting on them. They are also very cold, with the average temperature of Titania, for example, hovering around –203°C (–330°F). Furthermore, all the moons spend 42 years in darkness and 42 years in faint sunlight, which would not exactly prove ideal for the human body or mind.
Humanity could also happily bypass Neptune and move on to its largest moon, Triton. Little is known about this moon either, as only a single spacecraft (Voyager 2) has ever whizzed by. We know it is made of rock and nitrogen ice and has both cratered and smooth regions. The smooth areas are formed when geysers of dust and nitrogen gas erupt out of the moon’s crust. The dust then drifts gently back down, coating the surface of the moon. It has a slight atmosphere and might feel strangely similar to standing on the Moon or Mercury. It’s unclear, however, how dangerous the geysers would be but, as with any unpredictable eruption, establishing a settlement next to or near one would never be a smart move. Triton is currently the coldest known object in the Solar System with an average temperature of –235°C (–390°F), so a continuous energy source would be needed to keep a colony warm.
Pluto
This once-upon-a-time planet has been shrouded in mystery for so long that science can only speculate about what setting foot on it might be like. Depending upon where it is on its 248 Earth-year orbit, freezing temperatures can be expected down to –233°C (–387°F), and so we can kiss goodbye to the chance of liquid water. It has a tenuous atmosphere, created through the seasonal sublimation of ices on the surface, but is not thick enough to give the surface much pressure to work with – just 0.003atm (0.3 MPa/3mbar) – and due to its small size has only 1/15th the gravity of the Earth. However, NASA’s New Horizons probe has given Pluto a much-needed confidence boost (it was owed nothing less after the whole ‘not a real planet’ demotion) by revealing an incredibly geologically diverse and active world, even out in the farthest reaches of the Solar System. Should humanity ever figure out how to travel there in person, Pluto would display a number of useful attributes. This newly viewed second Red Planet is reddish owing to layers of haze stretching 160km (100 miles) into the atmosphere, while the surface is covered in flowing nitrogen-rich ice, similar to the movement of glaciers on the Earth, as well as ice volcanoes and snowfall. There may even be an underground ocean. Although setting up and maintaining a settlement on Pluto would be enormously complex and communications would be frustratingly slow, it would, scientifically at least, be well worth the endeavour.
Living in Space
At our current level of technology, the building of a space colony would present a set of extraordinarily great challenges. Space settlements would have to provide for all the material needs of hundreds or thousands of people, in an environment that would be very hostile to human life as we know it. Colonists would require systems such as controlled life support, which have yet to be developed in any meaningful way, and would be obliged to deal with isolation and confinement over many years, potentially for the entirety of their lives. The huge cost of sending anything from the surface of the Earth into orbit (roughly £15,000 per kilogram) gives an insight into the astonishing costs associated with building and launching a space colony.
As mentioned previously, humanity is already living in space and life on the International Space Station (ISS) provides a glimpse into some of the major challenges humans would face should we venture further into the Solar System. The ISS is a habitable satellite that orbits the Earth at an altitude of 355km (220 miles) once every 90 minutes, meaning that the Sun sets and rises for the crew nearly 16 times a day. It’s a vast project with shared ownership by NASA (USA), Roscosmos (Russia), JAXA (Japan), ESA (several European countries) and CSA (Canada), who all pitched in to build it. For the last 15 years there have been up to 10 astronauts at any one moment living in the vacuum of space above our heads, for up to a year at a stretch. Astronauts from all contributing space agencies have spent time there and the first British-ESA astronaut, Tim Peake, arrived for a six-month getaway in December 2015.
There are so many scientific and spiritual benefits of spending time in space, but it is the challenges and dangers that these real-life superheroes overcome to achieve these that tend to capture the public’s imagination and most certainly deserve our respect. The best-known attributes of the cosmic environment are that there is no oxygen or pressure in the vacuum of space. Daring to take an unprotected breath in space removes oxygen from the blood without replenishing it, so after 9–12 seconds, the deoxygenated blood would reach the brain, resulting in loss of consciousness. Two minutes later, death would follow. Blood and other bodily fluids would boil as the pressure instantly dropped, causing the body to swell to twice its normal size, but it would not explode, as commonly depicted in films – this is a myth. Another myth to debunk is that portrayed by the image of a frozen drifting corpse. In the vacuum of space, there is no medium for removing heat from the body, so in fact an astronaut is very unlikely to freeze to death. A vacuum flask is exceedingly good at insulation and keeping coffee hot, and it would also be true of your body warmth in space. Rapid evaporative cooling of skin moisture in a vacuum may create frost but this in itself is not fatal.
Without the protection of Earth’s atmosphere and magnetosphere, astronauts are exposed to high levels of radiation. A year in low-Earth orbit results in a dose of radiation 10 times that of the annual dose on Earth, which damages the lymphocytes in the blood – cells that are heavily involved in maintaining the immune system – and DNA itself. This damage contributes to the lowered immunity experienced by astronauts and potentially gives them a slightly higher risk of developing cancer later on in life. Thankfully, the crews living on the ISS are partially protected from the space environment as they are in a low enough orbit still to be embraced by Earth’s magnetic field, which deflects the solar wind around the Earth and the ISS. Nevertheless, a solar flare ejected from the Sun is still powerful enough to warp and penetrate these magnetic defences, and be hazardous to the health of the crew. Beyond the limited protection of Earth’s magnetosphere, however, interplanetary manned missions are much more vulnerable.
The greatest challenge, other than funding, facing human space exploration is not the technology required to achieve it, but the fragility of the human body to withstand it. To survive for a prolonged or even indefinite period of time in space, the effects and impact of long-term space travel on the human body must be properly understood, and for that there needs to be some voluntary test subjects – the astronauts. Technology has proven its ability to shield their bodies from many of the dangers of space, either by creating a life-support system to provide air, water and food and maintain comfortable temperatures and pressures, or by building a spaceship hull and habitat for shelter and protection against hazardous radiation and incoming micrometeorites. One aspect of a space-based life that cannot be avoided or protected against, however, is that of microgravity. If you have ever ridden a roller coaster and felt your body rise up as you crested the first huge hill and then plummeted towards the ground, you have experienced weightlessness. Imagine that feeling for maybe an entire year – no wonder over 40 per cent of astronauts feel nauseous. One astronaut, Jake Garn, was so unwell with space sickness that a new unit of measurement was named after him. The Garn Scale is now used as a gauge of how space-sick an astronaut is – the top level indicates when he or she just wants to give up and go home. What is surprising, however, is that the human body manages to adapt remarkably well to living in zero-g or, more precisely, microgravity. But the effects go far beyond the initial trip. Temporarily, weightlessness causes many key systems of the body to relax, as there is no longer the need to work against the pull of gravity. Astronauts experience disorientation as their sense of up and down becomes confused, which is why the ISS has all of its writing on the walls pointing in the same direction. Also, ISS occupants have reported losing track of where their limbs are and of feeling as if they are not there anymore. Spacecraft design takes into account all the effects of microgravity by putting extra foot- and handholds everywhere. A random fact: some materials – including human facial hair – tend to be more flammable in lower gravity. Thankfully, handling hazardous combustible materials on the ISS is taken very seriously and carried out with great care, so the risk of astronauts burning off their eyebrows is pretty low.
The longer astronauts spend in space, however, the greater the enduring impact the lack of gravity has on their bodies. Most famously, they experience deterioration of bone mass. The calcium in their bones oozes out through their urine, weakening the bones over time and simulating accelerated osteoporosis. This condition is thankfully mostly reversible once back on solid ground and in Earth’s gravity. Consequently, astronauts are much more susceptible to breaking their compromised bones should they slip and fall (those extra handholds come in useful). Sadly, an astronaut’s muscles also lose mass because while floating around is all very pleasant, a space traveller would literally waste away if that were all he or she did. Although astronauts have to exercise for two hours a day in orbit in an effort to counteract this muscle-wasting, they still require months of rehabilitation to build muscle back up again once they have returned to Earth. Astronauts also grow an inch taller while in space owing to their spine elongating, and they can develop a swollen moon-face as the body’s fluids move upwards. Unfortunately, this shift in fluids can also cause eyesight problems in astronauts, defined mainly by their seeing flashes and streaks of light. Much of this can gradually be reversed once back on Earth – but what if an astronaut were not returning to Earth? What would happen to the body then? The first one-year mission to the ISS launched in March 2015 conducted a unique experiment as US astronaut Scott Kelly has a twin brother, Mark, who remained on Earth. The brothers were then studied to observe the effects on Scott’s body in long-term weightlessness versus his brother’s on Earth.
A Space Oddity
Life in the cosmos also means dealing with a very distinct lack of personal space. Best-known of the challenges facing astronauts are long-term isolation, monotony, limited mobility and living in extremely close quarters with the same small group of people. The ISS is vastly larger than any previous space structure, about the size of a five- or six-bedroom house, but even so, staying inside your house for six months is hard to cope with both mentally and physically. Astronauts have cramped living quarters, privacy is a luxury, and they have to share everything with their fellow crew members for months at a time. The constant noise of people and machinery and the irregular light patterns make it difficult to sleep on board the space habitat, with astronauts commonly experiencing fewer hours of regular sleep and/or poor-quality snoozing. Combine that with the disruptions of the natural Earth day/night cycles en route and the result is stressed and fatigued personnel. Maintaining Earth standards of personal hygiene is also almost impossible as water is precious and showering in microgravity is not an option – but apparently this is a minor irritation and the ISS actually doesn’t smell too badly.
Surprisingly, although astronauts are physically removed from the Earth, they actually experience less isolation than scientists living in Antarctica in the height of winter. Regular contact with Earth, chatting with mission control, family and friends, as well as surprise calls from celebrities, via both video and voice chat and email keeps these space-dwellers thinking positively and feeling connected, giving them a respite from day-to-day chores and providing a sense of comfort and normality in an alien environment. The Internet and the advent of blogging and Tweeting, for example, may also ease the feelings of isolation faced in space, knowing that in cyberspace there is always someone listening. For five months, from December 2012 to May 2013, Canadian astronaut Chris Hadfield served as the commander of the ISS and gained a reputation as the ‘most social media savvy astronaut’ by sharing his daily life with the world, posting over 45,000 photos on Tumblr and Twitter and recording videos for YouTube. His guitar-playing and vocal performance of the late David Bowie’s Space Oddity and exchange of tweets with William Shatner of Star Trek legend were remarkable, considering it all was sent from space. For the first time, the ISS felt like simply an extension of the Earth. Hadfield himself said that posting the photos, and the immediacy of the reactions and collective sense of wonder he could share with people from all over the world, made him feel connected with the planet and to other people, even as he floated hundreds of kilometres above them. All those who have lived in space say they took great comfort in the view of and in communication with the Earth, but what if the journey meant that Earth became barely a dot on the horizon and communications nearly impossible?
Life in space has the potential to lead to depression, interpersonal conflict, anxiety, insomnia and even psychosis. Astronauts are living a life of risk. One rogue meteor or solar flare and it’s all over. But the considerable preparations made by astronauts aim to help them fight any negativity caused by months of living in fear and isolation. They train together for years as a team and as a family, so they already have camaraderie, a mutual understanding and trust, and to some extent intimacy with each other. Since outer space is considered an extreme environment, most training simulations and camps are also located in remote and harsh environments. The NEEMO mission sends aquanauts to the underwater Aquarius research station off the Florida Keys and several other analogue missions have been conducted on the Earth to simulate living in space or indeed on Mars. Most of these are research-based and were described in Chapter 5, but one – Hi-SEAS – is focused on the daily lives of people living off-world. Hi-SEAS (Hawaii Space Exploration Analog and Simulation) is a self-contained habitat found at an elevation of around 2,590m (8,500ft) on the slopes of Mauna Loa volcano on the Big Island of Hawaii. Terranauts live in a geodesic dome simulating life in a close-knit colony on Mars, including communication delays, isolation, cramped living quarters and, most importantly, food preparation. It’s no secret that pre-packaged, dehydrated space food is bland and the extent of seasoning involves pepper suspended in olive oil to stop it flying up and scattering around the station. Eating the same foods day in, day out can cause a syndrome known as menu fatigue, a common affliction at the ISS. The gastronomically bored astronauts end up consuming fewer calories, and ultimately lose weight and can become malnourished. NASA continually examines the daily lives of the crew on the ISS to see how they’re coping in a harsh and isolated environment, and to improve the agency’s plans for future long-term missions in space. Despite all the risks, there is no shortage of applicants for astronaut positions and virtually everyone who has had the chance to live in space is keen to return.
Fly Me to the Moon
We mentioned before the bodies in the Solar System where humans might one day make footfall, or at least how they might accomplish it should technology allow, but skipped over our nearest and dearest celestial relative, the Moon. Designs for and ideas about how humans might live on the Moon have existed since long before the dawn of the Space Age, but what is actually feasible today? And why the Moon?
The Moon is an ideal staging post where we can accumulate materials, equipment and personnel outside the confines of Earth’s gravitational pull, and it could be used as a test bed for the technologies needed to place humans on other worlds. From the Moon, we can send missions onwards to Mars or into deep space, set up astronomical observatories to view the cosmos without the interference of an atmosphere or Earth’s radio chatter, utilise lunar resources (mining deposits such as titanium and helium-3) and even support a bustling space tourism industry – who wouldn’t want to take a weekend break on the Moon? Humanity already has the means to get there and there are technologies that have proven advanced enough to sustain human and plant life in space. We just need the commitment and finance to proceed with it.
To build a habitat on the Moon is no easy feat. It requires consideration of how building materials will respond to the Moon’s vacuum; the extreme temperature variations between day (120°C/248°F) and night (down to –153°C/–243°F); impacts by micrometeorites (travelling at up to 10km/s or 6.2 miles per second); outward forces resulting from the habitats being pressurised for human survival; radiation damage; lunar dust contamination; and the gravity that is one-sixth of that of the Earth. These lunar habitats will be a lifeline for future colonists and as such will have to provide oxygen for them to breathe, water to drink, an environment in which to grow food, protection from the harsh radiation of the Sun, as well as light, warmth and power during the 14-day nights. They will also need to keep people comfortable in all temperatures. There are two types of water on the moon: first, from water-bearing comets striking the surface; and second, originating on the Moon itself. These could provide a potential source of drinking water, fuel, breathable air and protection for inhabitants: it just needs digging up. In 2009, India’s probe Chandrayaan-1 discovered more than 40 permanently darkened craters near the Moon’s north pole containing an estimated 600 million tonnes of water ice. Despite this huge potential store of water, over 90 per cent of that used in a future lunar habitat would be recycled. Recycled water would produce carbon dioxide (CO2), which could be pumped into a greenhouse for use by plants that would in turn produce oxygen as a waste gas, which could then be pumped back into the habitat. Power requirements of a habitat would require a stable and continuous supply of energy that could easily be generated by lunar solar farms. On Earth, solar power generation is limited at night, but on the Moon there would be the option of 24/7 continuous clean energy generation (which could in theory be channelled back to the Earth, as well as being used on the Moon).
With such a low gravity compared to that of the Earth, building a habitat for living and working would become quite a feat. On the positive side, engineers would be able to build structures less hampered by gravity and moving large objects would be far easier; they would just need to make sure they kept hold of these objects. Conversely, the low-g environment would pose difficulties for construction workers and their ability to move around easily. The lack of an atmosphere, however, would prove most damaging. Ignoring the obvious issue of a lack of air for inhabitants to breathe, without the buffering of air around drilling tools huge amounts of heat would be generated, causing drill bits and rock to fuse. Should demolition tasks be needed, explosions in a vacuum would create countless high-velocity missiles that would tear through anything in their path (including habitats and astronauts) and there would be no atmosphere to slow them down. Likewise, additional protection of habitats and inhabitants from meteorite impacts would need to be considered with no atmosphere to burn up incoming space debris. Also, ejected dust would obscure everything and settle statically, contaminating machinery, not to mention the huge health risk if the dust were somehow breathed in. The launch costs from Earth to bring building supplies would be astronomical, so local materials could and should be used wherever possible. Lunar regolith (fine grains of pulverised Moon rock), for example, could be used to cover parts of habitats to protect settlers from cancer-causing cosmic rays and to provide insulation. It is estimated that a regolith thickness of least 2.5m (8ft) would be required to shield the human body and reduce radiation exposure to a safe background level. High energy efficiency would also be required, so the designs would need to incorporate very effective insulating materials to ensure minimum loss of heat.
One design put forwards so far is a stereotypical inflatable dome, which would be lightweight and relatively easy to erect on the Moon’s surface. However, this would need good protection against incoming space debris, micrometeorite attacks, solar radiation and the vacuum of space. Lunarcrete or mooncrete could be made from lunar regolith, water and cement with the cement manufactured from lunar rock with a high calcium content. Water would either be supplied from sources off the Moon or by combining oxygen with hydrogen produced from lunar soil. Another option could be to manufacture habitats via 3D printing. In September 2014, a 3D printer was sent to the ISS to help astronauts print tools, parts and other much needed supplies. For the Moon, ESA has a plan. Prior to a human mission, they propose to send in a shuttle with an inflatable dome that would be erected on the surface as the founding unit of a future base. A robot and 3D printer would also be sent to create an exoskeleton that would line the outside of the dome and provide protection. Using dust available from the surroundings, ESA estimates it would take three months to get the base constructed and secure for up to four astronauts to inhabit.
Habitats could also be erected within ancient lava tubes. These form when the upper layer of a basaltic lava flow cools and hardens, and molten rock continues to flow beneath it. Once this drains, it can leave behind a hollow tube-shaped cavity. These natural cave systems provide a structure within which habitats could be built and easily sealed, the rock itself providing protection from the harsh surface environment and impacts. Such lava tubes are commonly interconnected, which would provide scope for the habitat to grow. A tube 1km (just over half a mile) in size or bigger would be ideal. The presence of lunar tunnels has yet to be confirmed unequivocally but spacecraft have revealed cave entrances known as skylights that may open into hidden lava tubes. Because of the Moon’s lower gravity, these are expected to be larger than those already discovered on our planet.
When prospecting for the ideal site for a lunar outpost, it should provide good conditions for transport operations, a range of useable natural resources and a number of targets of scientific interest. Yet, the success of a lunar settlement will heavily depend on the efficiency of its transport structure. It seems likely that transportation around the Moon will rely on wheeled methods, following from terrestrial vehicles and tried and tested Moon buggies from the Apollo missions in the 1960s and ’70s. To avoid mission-ending dust issues, it would be necessary to construct roads or potentially even a lunar cable car. One lunar colony could utilise the Shackleton crater at the Moon’s south pole, using the crater walls to enclose a domed city with a 1,520-m (5,000-ft) ceiling and a diameter of 40km (25 miles). A colony settled in that location would have access to large deposits of water ice and be situated on the boundary between lunar sunlight and darkness. Its proponents estimate that a Shackleton dome colony could support 10,000 settlers after just 15 years of assembly by autonomous robots.
Something to consider packing when moving to the Moon would be a good batch of microorganisms. Microbes are currently used in mining to help recover metals such as gold, copper and uranium as they can catalyse extraction of minerals faster than chemicals. In fact, more than one-quarter of the world’s copper supply is currently harvested from ores using microorganisms, in a process called bio-mining. Microbes could also be an important food source on the Moon. They grow faster than plants and generate more breathable oxygen than the same volume of vegetation, and they have a simpler growing process and are cheaper to transport as they take up less space. A peanut butter and microbe sandwich, anyone?! On Earth, Anabaena cylindrica is a nitrogen-fixing cyanobacterium and an extremophile to boot. When tested on rocks on Earth that are similar to lunar regolith, this microbe was able to extract calcium, iron, potassium, magnesium, nickel, sodium, zinc and copper from the material. It could also survive for 28 days under the extremely low temperatures and pressures found on the Moon, as long as it was shielded from UV radiation. This useful organism could also tolerate a decrease in water availability, so could happily be freeze-dried for transport.
Humans may not have set foot on the Moon since Apollo 17 over 40 years ago, but that doesn’t mean other life forms won’t grace the lunar surface again. NASA is teaming up with students and private space companies to grow the first plants on the Moon’s surface. The self-contained Lunar Plant Growth Habitat will resemble a glorified coffee can and will contain enough water, nutrients and air to grow 10 turnip seeds, 10 basil seeds, and 100 arabidopsis seeds on the lunar surface – Arabidopsis thaliana (Thale cress) was the first plant to have its genome sequenced. This experiment will test whether plants can survive the radiation, flourish in partial gravity, and thrive in a small, controlled environment – the same obstacles that will need to be overcome in order to build a greenhouse on the Moon, and ultimately for humans to be self-sufficient on its surface. When the mini-habitat lands on the Moon, it will automatically release enough water to wet a piece of nutrient-laden filter paper. That, along with the natural sunlight on the Moon, should trigger the germination of the plants. Completely sealed, the container will only contain enough air for about one week, but that will be enough to show whether the seeds germinate successfully. Interestingly, as a control, which every experiment needs, NASA are crowd-sourcing by sending schools across the USA their own set of habitats so they can grow the same plants that are being sent to the Moon. If the seeds successfully germinate on the lunar surface, this will be the first terrestrial plant life transported to and grown on another planetary body. The experiment is destined to hitchhike on board the robotic spacecraft of whoever wins the Google Lunar X Prize, saving millions of dollars in travel costs. The current price tag rings up at a mere $2 million – quite modest for an experiment that could help us figure out how to sustain life on other planets.
In the meantime, during his year in orbit on board the ISS, Scott Kelly successfully grew red romaine lettuce and a flower in space – an orange zinnia. Kelly had agreed with NASA to tend the plant as if it were in his garden on Earth, rather than according to a strict scientific regime. The zinnia soon flourished and put out several buds: a thrilling indication that cultivation of crops for food and medicine may be possible beyond our biosphere.
A Mission to Mars
Should colonisation missions head for the Moon first or Mars direct? Although the Moon is closer, easier to access from the Earth and has near-instant communication options, Mars is the world that seems to have captured humanity’s imagination as a future human outpost. Its formation and evolution are so similar to that of the Earth that we can’t help but want to study it, to learn more about our own history and future. Robotic explorers have studied Mars for more than 40 years – it is the only planet inhabited solely by mechanised beings – but a human presence is still a long way off. Mars today, despite its sub-zero temperatures, thin, non-breathable carbon dioxide-rich atmosphere, high UV radiation and savage global dust storms, actually has, as we have already explained, the most clement and almost welcoming environment in the Solar System after the Earth. It also contains habitable environments that could support microbial life, both in the past and even today in isolated areas.
At their closest point, a mere 54.7 million km (34 million miles) separates Mars from the Earth. One of the greatest barriers to humans making this trip, however, is the ability to carry the fuel needed. To travel these distances requires more fuel than just making a quick stop on the Moon, which means there is more weight to carry, and the greater the weight of a spacecraft the more fuel is needed to transport the weight. The total journey time from Earth to Mars could take between 150–300 days, depending on the distance between the planets at the time of launch and the rockets being used, so first on the to-do list would be to find a way to protect crews from radiation exposure on the trip. In May 2013, NASA scientists reported that a possible manned mission to Mars might involve a great radiation risk, based on the level of energetic particle radiation detected by the Radiation Assessment Detector on Mars Science Laboratory on its journey to Mars in 2011–2012. The Curiosity Mars’ rover received around 0.66 sieverts during its 253-day cruise to Mars – the equivalent of receiving a whole body CT scan every five or six days. In addition to this, large solar flares and cosmic radiation, although they can be prepared for, may still deliver a lethal radiation dose to a crew. Nonetheless, as mentioned in Chapter 7, a human crew to the Red Planet would be likely to receive only just above the limit of radiation currently deemed acceptable over an astronaut’s lifetime, and so the risk is judged tolerable in relation to the potential benefit to humanity resulting from their work.
Living in microgravity on the journey will cause the same physical effects as seen on the ISS, but these astronauts would then have to land on Mars and adjust to its gravity as quickly as possible. There will be no one waiting for them on the ground to help them out of the craft and to support them to start walking. The best way to assist the astronauts would be to remove the problem and produce artificial gravity by spinning the spacecraft as it travelled to Mars, adjusting the gravity slowly to help the astronauts adapt before arrival to life on Mars.
Another worry is the risk of supersonic space dust. In 1967, a stream of micrometeorites ended the three-year-long Mariner 4 mission, while in 2012 a micrometeorite slammed into one of the ISS’s giant windows. Space shuttles have all returned to Earth with mini impact craters on their hulls. The ISS now has a micrometeorite shield on the exterior of the Zvezda Service Module, which any Mars shuttle would also need. Finally, although this is not the end of the list of worries by a long shot, there is the issue of landing. The current success rate for setting down safely and in one piece on Mars is only 30 per cent. With a human at the controls, the rate may be higher – NASA did not lose any of its Apollo landers during touchdown on the Moon. However, unlike the Moon, Mars has an atmosphere and its gravity can make a soft landing much more challenging.
Building an outpost on Mars will require a great deal more planning, even though we would have far better conditions to work with than are present on the Moon. The benefits of moving to Mars are that it has a similar length of day and the planet is tilted on its axis at an angle comparable to that of the Earth, which creates similar seasons; and it has an atmosphere, water ice, and habitable environments. There is a number of geological landforms, such as impact craters and lava tubes, which could be used to house habitats, as proposed for the Moon, and there is a never-ending list of scientific investigations that could be carried out. Larger habitats would be required for long-term living (the only real way to live on Mars), which could be built in stages during a series of launches, taking inspiration from the piece-by-piece construction of the ISS. The parts for a Martian base could be delivered by landing modules in a series of missions, which could then be assembled by a human crew either already on the surface or arriving later, by robots or even by a crew based on a nearby Martian moon. Buzz Aldrin, the second person to walk on the Moon and a great advocate of Mars colonisation, suggested sending three people to spend 18 months on the moon Phobos, using this as a headquarters from which to remotely construct a base for Mars.
The environment on Mars is the main challenge to overcome for any human or habitat as its 95 per cent carbon-dioxide-filled atmosphere is toxic to humans and promotes low atmospheric pressures (0.006atm/0.0006MPa/6mbar). Additionally, it only has 38 per cent of the Earth’s gravity, is always cold (–85°C to –5°C/–120°F to 23°F), and there are no liquid bodies of water on its surface. As for habitats on the Moon, oxygen would need to be generated for humans to breathe and suits would need to be worn whenever the inhabitants left the outposts. Owing to the time taken to travel between Mars and the Earth (not to mention the cost), a habitat on Mars would need to be self-sustaining from day one, growing its own food, extracting its own water and producing its own oxygen. Even though many studies are being conducted into the logistics of how this might be achieved, it is still very likely that a spacecraft would stay in orbit with food and supplies for a journey home, and also for a safe haven in case something went wrong on the surface. With costs of £50,000 to ship 4 litres (7 pints) of water to the Moon, imagine the cost, let alone the logistics, of shipping water and food to Mars on a regular basis. The only logical key to long-term human habitation of Mars is space agriculture or astro-gardening.
The first Martians will therefore be two species – plant and human – who are actually perfect travelling companions. Humans consume oxygen and release carbon dioxide. Plants return the favour by consuming this carbon dioxide during photosynthesis and releasing oxygen. Humans can use edible parts of plants for nourishment, while human waste and inedible plant matter can (having been broken down by microbes in tanks called bioreactors) provide nutrients for further plant growth. Plants need water, oxygen, sunlight, nutrients and relatively comfortable temperatures, but none of these are currently found on Mars in quantities that suit the growth of a garden. With a lower gravity than the Earth and ravaged by global dust storms, this is a world that would not support most known plant life. Plants are a canary in a coal mine for human habitation – if they cannot find a way to survive, then we cannot either. Gardening on Mars would provide a long-term food source for future human colonies and could provide over half their required calorie intake through the growth of tomatoes, potatoes and other fruit and vegetables. Plants that thrive in the carbon dioxide rich atmosphere of Mars include seeds of radish, alfalfa and mung bean, while asparagus, potatoes and marigolds have been shown to grow in Mars-like soils. If Mars gardeners are to use Martian soil, then knowledge of how crops respond to its contents, such as sulphates and perchlorates, will be required. Gardens help to recycle nutrients, and provide drinking water and in the longer term could provide building materials such as wood and bamboo. Any garden would need protection in the form of a greenhouse or geodesic dome that could keep the crops sheltered from extreme UV radiation, while still allowing in enough sunlight for growth. This dome would need to be securely anchored into the regolith to provide support and stability against the fearsome Martian dust storms and dust devils. The crops would also have to be kept warm while surrounded by the cold climate of Mars. This heating of the greenhouse would require energy, potentially from solar panels arranged outside the habitat and heating filaments beneath it; although that energy source too would require protection against the Martian environment. Accessing liquid water is a given since it would be needed both for irrigation of the plants and for human consumption.
Terraforming
When humans finally make it to Mars, we will live in a similar manner to how we do in Antarctica. Mini enclosed Earth-like environments will arise on the Martian surface that could include not only gardens and homes, but also parks, forests and lakes, all maintained under an Earth-like air pressure through a process known as paraterraforming. While it would cost a great deal of money to construct, paraterraforming sections of Mars with a sample of Earth’s biosphere inside pressurised domes and underground caverns is something that humanity could achieve within mere years of arrival. Eventually, however, there would be an even more ambitious goal that might take millennia – full-scale terraforming. This is the process of ‘transforming a hostile environment into one suitable for human life’, as defined by NASA, although this is a dated and distinctly Homo sapiens-centric view. I prefer terraforming as the process of making a hostile environment suitable for life – not necessarily human life, which needs very specific conditions that are hard to achieve. Essentially, we are saying that one day we could bring Mars back to life. But why would we want to do this? Is it for the art of doing it, for the science, for the economic necessity or is it to leave a legacy for the planet Earth?
Terraforming Mars would entail three major interlaced changes: building up the atmosphere, keeping the planet warm enough to allow liquid water to remain stable on its surface and, finally, protecting the atmosphere from being lost to outer space. Most of the legwork would be done by life itself. You would not build Mars … you would just warm it up, throw in some seeds and allow life to take over. First, the atmosphere would need to be thickened and enriched with nitrogen and oxygen while the average temperature of the planet would need to be increased substantially. Perfluorocarbons, potent greenhouse gases, could be synthesised from elements in Martian dirt and air and then blown into the atmosphere. Through warming, the planet’s frozen carbon dioxide in the ground would be released, which would amplify the temperature and boost atmospheric pressure to the point at which liquid water could flow. Terraformers might then seed the red rock with a succession of microbial ecosystems to increase the amount of methane in the Martian air, because methane is a much stronger greenhouse gas than carbon dioxide. First, bacteria and lichens (which have survived in Antarctica) would be grown, then later mosses. As dark plants and algae spread across the surface, they would darken the planet so that it absorbed more sunlight, and after a millennia or so, forests would be growing. With the right combination of plants and well-selected microorganisms, planetary engineers could generate the critical oxygen and nitrogen needed for human inhabitants to roam the surface without a space suit. Throughout this process, colonists would continue to inhabit Mars and expand the system of enclosed mini Earth-like habitats.
However, before we start this irreversible process of Martian environmental change, we need to be sure that we are not treading on the toes (if they have any) of any hidden life forms on the red planet. As we push Mars towards being more Earth-like, are there organisms present that might push back? We know that Mars has organic compounds that could be used by life, but a pessimist would say that any life that did exist there has not survived intact today. So if we are to bring Mars back to life, should it not be with native Martians rather than with Earthlings? The ingredients of the biosphere, if at all possible, should have Martian DNA at its core. Perhaps if we could find the relics of past Martian life frozen beneath the surface, in the polar ice caps, or living in some sub-surface refuge as we do on Earth, we could reconstruct it and let it once again control biogeochemical cycles on Mars. We could give Mars back its heartbeat. Sending life from Earth to colonise Mars should be an absolute last resort. Only if Mars has no genome should we consider sharing ours with it.