Space exploration: our future

Thursday 8th April 2010
Submitted by Louise Ridley
Our future in space

Step one: Find a base
Step two: Build a home
Step three: Mine space
Step four: Go long haul
Step five: Meet the (alien) neighbours
Step six: Evolve

 

Step one: Find a base 

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Award-winning science fiction author Stephen Baxter searches the Solar System for the best place to terraform.

 

Do you dream of living away from Earth? It’s an old ambition, but has plenty of modern-day logic behind it. As well as the traditional motives of science, exploration and national prestige-building, increasingly there is a commercial drive behind space development. And private enterprise is playing a bigger role because governments are finding it harder to justify and fund space programs, as President Obama’s decision to cancel NASA’s Constellation Project proved.  Tourist trips to Earth's orbit are on the horizon. And as traditional fuel sources on Earth gradually fail, over the coming decades, resources from space may underpin continuing economic growth, and may be a solution to other difficulties like environmental stress. Space-borne power generating facilities, for instance, would drastically reduce the pressure we place on the planet’s environment in terms of heat production and pollution.

Asteroid mines and orbiting power stations are likely to require miners and engineers living off-planet for extended periods – colonists in space. But how are we to achieve this? The Apollo astronauts carried with them to the Moon every scrap of food, water and air they would need during their journey – and so they were restricted to a stay of just three days. Humans have lived in Earth orbit for a year or more on the space stations, but while the International Space Station practises some recycling, all our stations have basically relied on food and other supplies brought up regularly from Earth. If we are to live and work permanently away from our planet, we must learn, one way or another, to live off the land (see Step 3: Mine space). But first, we need to create a base…

 

Lunar challenges

Terraforming – making a world into a clone of Earth – is usually associated with Mars. The Red Planet may seem the obvious choice, but the first place we may try to settle is the Moon. Our nearest neighbour has as much land area as North America, almost all of it unexplored, and is a relatively easy three days’ travel away. What’s more, the lessons we learn on the Moon will help us when we reach more distant and challenging destinations.  Before the Apollo missions, it was a given for space visionaries that we would live and work there, and that the Moon would become a portal to opening up the Solar System. The key was finding water. We need a lot of ingredients to keep us alive, but water is by far the most fundamental; by comparison, carbon, hydrogen, nitrogen and other essential elements amount to only fractions of the mass of living tissue. It seems a fair bet that wherever we go, if we can find water, we can find a way to live. And as we consider destinations that lie even further out, water will be regarded as a key goal, so we must follow it.  Water not only supports life, it can be ‘cracked’ with electrolysis into hydrogen and oxygen to supply rocket fuel. So, if water was present on the Moon, with power from the Sun, it could be a filling station outside Earth’s deep gravity field. It would be much easier in terms of fuel costs to land on and depart from, and could be used to support a general expansion into the Solar System. Apollo brought a grave disappointment though. The analysis of Moon rocks showed not the slightest trace of water. Suddenly the Moon became much more difficult a target for colonisation. But not impossible – Apollo left most of the Moon unexplored. Now we believe there is water there after all. It may be frozen in the shadows of the lunar poles. NASA’s recent LCROSS mission detected traces of it spread thinly in the lunar surface soil. But colonists may have to strip-mine vast areas of the surface to get at it. You would also have to import from Earth most of the essentials for life, such as other atmospheric gases, and then recycle and hoard them ruthlessly. The Moon’s low gravity would cause any new atmosphere to leak away, admittedly slowly. And the lunar conditions would invalidate much of our terrestrial experience of heavy industry and manufacturing – for instance, most lubricants would be useless in the vacuum. Plus, the Apollo astronauts found that the corrosive lunar dust destroys seals and joints.
Biospheres could be the answer. But, whether on the Moon, Mars or suspended in an orbital station, there are common challenges in maintaining small artificial biospheres for long periods, with closed loops of air, water and other essentials. We don’t know how to do this yet; small biospheres tend to be unstable, as discovered from the Biosphere II experiment in Arizona in the 1990s. Even then, the Moon’s month-long ‘day’ would cause problems; the new lunar atmosphere would freeze out during the long nights – as in HG Wells’s First Men in the Moon. Perhaps some remedy like spaceborne mirrors to stop the freezing could be deployed – or even, ultimately, spinning the Moon. And the lack of any geological activity would mean that, in the very long run, the Moon couldn’t recycle its store of essential volatiles, as Earth does through tectonic cycling, involving the movement of continental plates.

In short, the inhabitants of the Moon would have to manage its maintenance on a global scale far into the future. So the question is, why would we actually want to put a colony there? 

There would have to be strong commercial reasons for colonising the Moon. The good news is that there are. Aside from the Moon’s history – all those Apollo landing sites waiting to become tourist attractions – the satellite is also rich in common and useful elements. Hydrogen and helium may be present, implanted in the lunar soil by billions of years of solar wind. Silicon, aluminium, calcium, iron, titanium and magnesium have also all been found in the Apollo rock samples by scientists and engineers at NASA’s Lunar and Planetary Institute in Houston. 

And, while Moon rocks contain no water, they are 40 per cent oxygen by weight. NASA engineers at Houston, working with fake Moon rock, or ‘simulant’ as they call it, have trialled technologies for baking out the oxygen, by blowing hydrogen across crushed rock. From lunar rock you can make ceramics, concrete and glass. The engineers found that the absence of water is actually an advantage for the manufacture of glass, which can be made much tougher than on Earth. In the lunar cities of the future, it could serve as steel or concrete does in Earth cities. And structures of lunar glass could be ‘exported’, lifted easily out of the Moon’s low gravity, to construct habitats in Earth orbit and beyond. 

The first lunar colonies may be tourist resorts, owned by and perhaps only accessible to the elite rich. But the real drive for living in space would be the ‘gold rush’ for resources (see Step three: Mining the moon). In time, the colonisation footprint would grow, and the technologies would mature – and become cheaper. With hard work you could build a home there (see Step two: Build a home) and make a living. And from Earth, the face of the colonised Moon would be transformed, with glittering solar-panel farms, the vast rectilinear scars of the strip-mines, and gleaming jewels of glass cities. 
 

Paraterraforming

surface of MarsThere are intermediate steps between dome-city colonisation and full terraforming. ‘Paraterraforming’ means the construction of enclosed environments spanning large portions, or even all, of a planet’s surface: a roof covering the Sea of Tranquillity, or even all of the Moon. These would offer many of the advantages of full terraforming in terms of room to grow, without the large energy costs involved. But a paraterraformed world would be vulnerable, for instance to meteorites.

Again, the Moon would be a test bed of common problems to be addressed when considering the terraforming of other bodies. All the likely candidates from Mars outwards are smaller than the Earth, so low gravity and a lack of tectonic recycling would always be an issue. Many of them, just like the Moon, lack key volatiles, which might have to be transported across the Solar System. As well as ecological problems, small closed communities would raise unique ethical and political issues. How do you ensure freedom in a domed city where the very air you breathe has to be provided by machinery? Early civilisations in some arid regions of Earth became ‘water empires’, such as the Sumerians from the third millennium BC, where control of the water supply was essential for survival – and effectively gave total power to a central elite. In a confined space, different groups, perhaps divided ethnically or on religious grounds, would have to learn to get along better than we’ve managed so far down here on Earth. Especially as there would be nowhere else for them to escape to. The essential machinery of life would have to be made robust, not just mechanically, but in case of deliberate acts of sabotage and terrorism.

You may have chosen to live on the Moon, with all its constraints and disadvantages. Maybe your kids won’t thank you for raising them in what is effectively a cage. Historically, most colonies have grown towards independence from their parents. The lunar colonies may be more dependent on supplies from Earth than, say, the American colonies were dependent on imports from Britain. What happens when cultures diverge, and a call for independence grows? A threat by Earth to cut off the top-up water supplies would be a serious one.

 

Colonisation conscience

Even if we could terraform the Moon – or Mars, or other worlds – should we? Proponents of terraforming would say that a living world is always better than a dead world: that to give life is the greatest gift humans could bestow. But right now we don’t know if Mars, for example, has its own life or not; perhaps we should investigate that fully before wiping out any traces of it forever. Even if a world is lifeless, is it wise for us to rebuild it? There is the question of good husbandry. The primeval worlds, once gone, are gone for all time; who knows if what we do now is making the best use of them.  And there are more ways to treat a landscape than to pave it over. Science fiction writer Brian Aldiss has argued that we should think of Mars, for example, as an Ayers Rock in the sky. Mars, like the Moon, is very unlike the Earth, but it has a grandeur and appeal of its own. Mars and the other worlds have more to offer us than crude physical resources; they are resources for the spirit as well.  So you dream of living in space? A space colony may start as a tourist trap. But the first true space colonies will most likely be mining towns that evolve into living human communities (see Step three: Mining space) in a setting unimaginable to previous generations. What you find out there may make you rich, but it will also transform you and your children, and perhaps the worlds of the Solar System themselves. (Back to menu)

 

 

Step two: Build a home 

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Could we create a viable community on another planet in the near future? Clearly, it’s not going to be easy, but that hasn’t stopped researchers beginning to tackle the problem, in particular, imagining how mankind might live on Mars.

Any settlement on the Red Planet, if it’s to be anything other than the Solar System’s most expensive and inaccessible sleepover science lab, will ultimately need to be self-sustaining. Initially, that will mean sending huge amounts of equipment, much of it on unmanned craft, to get started. Choosing the right mix of kit will be key: lightweight inflatable habitats are comparatively easy to transport and would provide near-instant shelter, but equipment that helps settlers to make building materials such as bricks will likely be more useful in the long term. The illustration below is based on ideas put forward by the Mars Foundation.

Terraform Mars

1. Water tank - While settlers will need to locate and harvest groundwater or ice, H2O will still be a precious resource so all wastewater will be carefully recycled and reused.

2. Living quarters - Private areas may seem like a luxury, but any settlement ultimately needs to be a true home for scientists and settlers who will be away from Earth for months or years on end.

3. Power plant - Martian settlers will need an industrial capability and be able to guarantee sustaining an oxygen-enriched atmosphere in habitats. This means reliable power supplies will be essential, possibly a mix of solar and nuclear. 

4. Pressurised habitats - Settlers will use steel, aluminium, glass and bricks manufactured on Mars to build habitats that can be extended as an initial settlement grows to become a town. Multiple habitats are a guard against a unit failing. Robots may do some of the initial construction, paving the way for crewed missions.

5.Greenhouses  - Growing fresh food on Mars will be essential, but there will likely need to be other areas of greenery too – growing bamboo would both have psychological benefits and provide a handy building material. (Back to menu)

Step 3: Mine space 

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Forget the Hollywood idea of shiny spacesuits and utopian living. Award-winning author Dr Stuart Clark explains why once the elite tourist rush is over, the first true space colonies are going to be ‘gold rush’-style mining towns.

 

Mining spaceThey’ll be industrial bases constantly in search of new resources to exploit: materials to build with, water to drink, rocket fuel to get home with, even air to breathe. Astronauts are going to have to live off the extraterrestrial land, no matter how hostile it may seem. This is the only way that space colonies will be possible – we have the strength of Earth’s gravity to blame for that. We can just about struggle into space, dropping off spent rocket fuel stages as we go, but the harsh reality is that if Earth were just a few per cent bigger, chemical rockets wouldn’t work at all. They’d be incapable of reaching orbit because they 3 3 wouldn’t release enough energy to escape the enhanced pull of gravity.

Cutting costs

As it is, lofting heavy satellites or machinery into space is very expensive, costing roughly $10,000 to launch every pound of weight into orbit. If you want to then land that payload on a different world, the price goes up even further because, to land safely, you need more fuel and rocketry to counteract the pull of the destination. For the Moon, the price goes up to $50,000-$100,000 per pound. For Mars, the price is steeper still. “That makes every pound you launch into space more valuable than solid gold,” says Peter Curreri of NASA’s Marshall Space Flight Center. The key to cutting costs is not to take everything you need, but to make much of it when you get there. This concept goes by the acronym ISRU, or In-Situ Resource Utilization, although some proponents are currently re-branding it Space Resource Utilization (SRU). “Anything you can use once you get there saves you a lot of money,” says Curreri. Rich real estate Curreri deals in fake Moon rock. He’s not a dodgy eBay scammer, but a materials scientist who has been showing how to extract rocket fuel from lunar dust. He manufactures fake Moon rock, or ‘simulant’, because the actual Apollo samples, brought back from the Moon are far too precious to melt. In particular, Curreri is after oxygen, which comprises 40 per cent of the composition of Moon rocks. Once oxygen is mixed with hydrogen it can be used as rocket fuel, transformed into water, or simply employed to supply a lunar base with breathable air.

The process needed to extract the oxygen is electrolysis, and it will be similar to extracting aluminium from ore on Earth. Electrolysis passes an electrical current through a molten sample, which drives chemical processes that don’t occur in nature, to separate the oxygen from the other components in the Moon rock. The oxygen is then collected for further processing, as are the by-products, which in the case of the Moon are metals such as aluminium, silicon, magnesium and iron that can then be used to cast equipment.

Moon elements

Helium is another element that’s thought to exist on the Moon, but is rare on Earth. British space researcher Bob Parkinson has suggested that particular isotopes of helium, essential for fusion power stations, could be a valuable export. The astronauts will still have to take the bulky equipment to extract the element, but once on the Moon and working, it should soon pay for itself. “The Moon is probably the most valuable real estate in the Solar System. It’s got everything you need,” says Curreri. “It’s close to us, has low gravity, is a good source of metals, and has volatile material in the polar craters.” By ‘volatile material’ Curreri means ‘water’. Water is the greatest resource that could be found on any extraterrestrial body because it’s made of oxygen and hydrogen. You can drink the water, breathe its oxygen and produce rocket fuel to get you home. It turns out that the best place to find water is not where Apollo landed, near the equator, but at the poles. Water is now known to exist in significant quantities there.

The recent NASA mission LCROSS (Lunar CRater Observation and Sensing Satellite) crashed a large impactor into a crater called Cabeus, which has a floor that sunlight never reaches. In that perpetual darkness, water lies frozen in sheets that Curreri thinks could be mined. “The idea is to set up a base near the crater and then use rovers to crawl down into it and extract the water,” he says. The rovers would be miniature refineries, harvesting the precious liquid from the crater floor. Such lunar resources could also be exported across the Solar System. The lunar gravity is just 1/6th that of Earth, which means you only need 1/20th of the energy to launch from the Moon into orbit. Space engineers envisage devices known as mass drivers, which accelerate payloads down a track using a magnetic field. The track would tilt upwards and when the payload shoots off the end of it, it would be travelling fast enough to reach orbit and beyond.

The ultimate places to mine if you want to ship the proceeds around the Solar System are the asteroids. These mountain-sized lumps of rock have no appreciable gravitational fields yet contain many of the same resources as the Moon. Hence, launching materials you mine from them into space is easy, requiring hardly any fuel at all. They’ll prove invaluable when constructing space stations and rockets in orbit.
 

Precious metals

Many asteroids appear to possess extraordinary concentrations of precious metals. In the case of platinum, some are estimated to contain 10-20 times the concentration found in mines on Earth, making them highly valuable. And because of their low gravity, some near-Earth asteroids require far less rocket fuel to get to and land on than the Moon, although they are further away. The next destination for humans in the Solar System is Mars. Here, living off the land takes a marked upturn as the 3 3 Red Planet has even more to offer than the Moon.

On Mars, the first thing to mine is the atmosphere rather than the soil. It is almost completely composed of CO2, although it exists at a pressure of just 4/1000th that of Earth’s atmosphere. Douglas LeVan from Vanderbilt University, has developed equipment based upon a device called an adsorption compressor. This will trap CO2 from the Martian atmosphere and then heat it to boost the pressure. Once pressurised, it will pass through an electrolytic device that causes it to release pure oxygen. The remaining carbon monoxide can be captured and used to make plastic components. “We have demonstrated that this technology works well in the lab,” says LeVan. The overwhelming priority on Mars will be to make rocket fuel. The plan is that robotic refineries will be sent to Mars long before astronauts. These automated stations will work to generate enough oxygen for a return human trip and only when the tanks are full will the manned missions set off from Earth. American engineers Robert Zubrin and David Baker proposed such a mission design in 1990. Since that time, Zubrin has championed the idea to make Mars missions feasible. NASA now agrees with him, has funded a number of research proposals into the necessary technology, and sees it as essential to a successful Mars mission, although, at present, there is no fixed timescale for such a mission.

When it comes to space exploration, there’s no doubt that the first astronauts will have to be as skilled in mining and farming as they are in rocketry and astronautics. It’s the only way mankind will conquer the other planets. (Back to menu)

Step four: Go long haul

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Want to travel beyond the Solar System? NASA rocket scientist Marc G Millis knows how to do it. He tells Daniel Bennett how we could cover cosmic distances. 

Nasa scientist Marc G Millis

What will replace the rocket?

One possibility is something I call the Bias Drive. To give you a rough idea of how it works, fill a sink with clean water and put something in it that floats. If you touch the area just behind it with a tiny drop of detergent, you’ll see that the boat rapidly moves away. The boat is analogous to a spacecraft. It had no propulsion on it – what you did was change the water. In other words, rather than having a vehicle that has an engine built into it, you locally change the properties of space around it, which then reacts against the vehicle and pushes it forwards.

What would be the best way to power a mission to colonise Mars? And how long would the journey take?

It’s debatable, but three months is a fair average. That would probably be using some form of nuclear propulsion. Despite the vivid negative images associated with it, when it comes to deeper space flight to places like Mars and further afield, nuclear power is so promising because of its energy density. Although it would have to be some sort of mixture between nuclear power, chemical rockets and even electric propulsion, using things like xenon and ion thrusters [an electric propulsion method suited to deep space exploration that harnesses negatively charged particles]. There is no single best way because there’s so many ways to make missions like that possible. If we send automated, unmanned colonisation vehicles first, we won’t care if they take a year or two to get there, so they would have an entirely different propulsion system than if you just sent a human crew.

What would be the fastest way of visiting neighbouring stars?

If you’re talking about what’s the fastest way we can start, then we’re probably looking at solar sails, which harness light for propulsion. But then the main issue is something we call the ‘incessant obsolescence postulate’, which says that no matter what probe is sent now, a more modern probe will pass it in the future and reach the destination sooner.

Does science fiction help your work?

The stories help me focus on what it is I actually want to accomplish. Robert Forward, a famous aerospace engineer and science-fiction author, said his writing helped him work out the technical problems of solar sails. He would use the scenarios he described to identify the most important issues. It
can be a thought-provoking tool and a way of focusing on the problems that need solving.

Star Wars or Star Trek?

I was a huge fan of Star Trek when I was growing up and that inspired most of my science fiction-esque thinking. I loved the way it expanded your mind. I used to think it was educational – not in the sense of information, but in the sense of stretching the mind. 

Do you still enjoy science fiction now?

I did go see the last Star Trek movie, and Avatar, but it’s not the same as when I was a kid. Now I’m more interested in whether the technology looks plausible. There’s been very little science fiction recently that has triggered really deep thoughts in me about how you would do something. There hasn’t really been anything beyond warp drive and hyperspace in the decades that they’ve been in existence. I’d really love to have my brain stretched like that again. 

When ‘Warp Drive’ and ‘Hyper Space’ travel are shown in films, they work by stars converging to a point before the ship darts into them. Is this really what faster-than-light travel might look like?

We know reliably that as you start from zero speed and approach light-speed, you begin to move at a similar speed to the information you’re getting about the Universe around you, which means the information gets distorted. So you would see all the stars and star fields in front of you start to collect and wrap themselves around the front of your view. Beyond light-speed it would probably be black; by then you’re no longer able to interact with light because you’re going faster than it. But that’s purely speculation.

Space drives, zero point energy and wormhole manipulation, and are all freakishly interesting topics you’ve been lucky enough to work on. But do you ever get bored of your job?

There are certainly moments of fascination and excitement, usually when I’m in a group debating things for fun. But there’s the other part of the work when I’m reading reports and thinking through the ideas – going through the gory details – where it’s hard work. Bored? No. Frustrated and exhausted? Definitely. (Back to menu)


Step five: Meet the (alien) neighbours

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If we move to another world beyond our Solar System, what would the creatures on the planet ‘next door’ be like? Our new neighbours would be familiar in some ways, says Lewis Dartnell, but there’d also be a few surprises…

 

SpacemenAs humanity explores the Universe hunting for new places to live and exploit, we will undoubtedly find more and more Earth-like planets. Here, evolution will have had the opportunity to produce a diverse array of complex plant and animal life forms. And that raises an intriguing question. What might our alien neighbours look like?

Well, combining our understanding of planetary science and evolutionary biology we can have a pretty good stab at predicting what we’d expect to find. Those principles show we’d be nipping to borrow some sugar from some pretty strange creatures.

Laws of physics

Life developing on worlds throughout the Universe will be subject to exactly the same laws of physics and engineering as here on planet Earth. Certain adaptations, like eyes or wings, are so useful that evolution has hit upon them independently time and time again. They are universals of terrestrial biology and we’d expect similar solutions to develop on other worlds. In fact, in many important respects we’d expect our extraterrestrial brethren to look pretty familiar. But, life evolves to prevail under the environmental conditions it’s exposed to, so the strange environments out there would produce some weird adaptations – or they’d be weird to us at least. 

The first thing we can say is that for multi-cellular life that needs a lot of energy to survive, the planet’s atmosphere must be rich in oxygen. Burning carbon-containing compounds like glucose in oxygen provides more energy than any other feasible biochemistry, so we can be pretty sure that alien animals on any Earth-like world would enjoy a deep lungful or gillful of the stuff as much as us. 

Other aspects of alien anatomy are likely to be instantly recognisable – a through-flow tube-like gut with a mouth and an exit for efficient digestion of food, a network of internal veins and pumps to transport nutrients and oxygen around the body’s cells, and a rigid framework for support, either internally (like our skeleton) or externally (like a crab’s carapace). A variety of sense organs are needed to navigate the world, track down tasty morsels and avoid predators, and a centralised cluster of nerve cells to process all this information would allow quick reaction times and direct the animal’s behaviour.

Eyes and a head

Eyes are an effective method of surveying the environment, and it makes most design sense to have these at the front of the body close to the brain, protected inside a hard case – a head. 

On the other hand, many features of Earthly evolution may not actually be the optimal solution to any survival problem. They might just be accidents of history. For example, humans have
10 fingers because the ancestor of land vertebrates just happened to have a limb with five digits. An intelligent alien could just as easily clasp tools with four fingers and count in sets of eight. Likewise our body-plan based on four limbs is thought to be an evolutionary accident – our fishy ancestor had two pairs of lobed fins rather than three. 

Alien plants and trees would strive to balance the need to collect light with the dangers of drying out and toppling over. The light-harvesting pigments in plants have evolved to best soak up the particular spectrum of light from our Sun. Alien plants growing by the light of other suns, shining more red or more blue, would need to be tuned to a different spectrum and so sprout leaves of a different colour. 

So when our explorers do make footfall on these new worlds, they’ll almost certainly find many design features of our neighbours uncannily familiar. But evolution would also have crafted some surprises. (Back to menu)

Step 6: Evolve

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Stephen Baxter considers the effect a future in space will have on us as a species.

Humans are African animals who have colonised the whole Earth. While we could not have survived without our technology in extreme areas such as the desert and the Arctic, natural selection has worked on us to make us fit for each environment. The inhabitants of cold polar regions tend to be short and round, minimising surface area and so heat loss, while those of the hot equatorial savannah are generally tall and thin. 

As we spread across the Solar System and beyond we will surely continue to evolve to fit each new environment. Some of this may be by conscious design. We may engineer our children genetically to better withstand the long-term health effects of zero gravity such as the loss of bone mass. More drastic engineering is possible; in zero gravity a flipper tail like a mermaid’s may be more useful than legs. On high-gravity worlds, conversely, humans may become squatter and stronger – like Neanderthals. 

We may decide that a wiser strategy than terraforming worlds would be ‘pantropy’. This is where humans are modified, possibly through genetic engineering, to survive and thrive in the existing environment – adjusting ourselves to meet the Universe halfway. Frederik Pohl’s 1976 novel Man Plus depicted a human adapted to survive on the surface of Mars, with solar-sail wings and multifaceted eyes.

But natural selection will continue to work on us regardless of our conscious intentions. The enclosed environments of dome cities, orbital habitats and long-duration spaceships will be like islands on Earth, ecologically – and on islands you typically get ‘dwarfing’, as animals become smaller to make the most of limited resources. Humans in Martian dome cities may be miniature, like the ‘hobbits’ of Indonesia.

In the very long term, there may be no limit to the changes wrought by evolution. Our ancestors’ form has proved plastic in the past. The modern human body form dates back to Homo erectus, and is the result of a drastic rebuilding of a forest-dwelling chimp-like creature for survival on the open, arid savannah, with bare skin for temperature control, and fatty water stores in the buttocks. Will evolution similarly rebuild our distant descendants on Mars or Alpha Centauri III? We may not recognise them as human at all.

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