Which Planet Should We Terraform Next?

Which Planet Should We Terraform First?

Humankind has long dreamt of setting up a second home, with our gaze usually set on Mars. But, is the Red Planet really where we should be heading?

This is Unveiled, and today we’re answering the extraordinary question; Which planet should we terraform first?

To “terraform” means to shape and modify another world into something suitable for human life. It’s different and more complicated than simply building state-of-the-art space bases, though, because it’s about permanently changing the environment - creating Earth-like conditions. In fact, some argue that we should start with the Earth itself - focussing on our own planet’s most inhospitable environments to both better our own lives and ‘test run’ for future projects further afield in the solar system.

After that, it’s all systems go for Mars. Apparently. Thanks to various landers, rovers and probes, we’ve been busily mapping Mars for decades - but it’s by no means a simple task to make it liveable. NASA, SpaceX and everyone else are attracted to Mars because it does boast the four key elements needed to support life – carbon, hydrogen, oxygen and nitrogen – as well as water, and it once had an atmosphere. There are a few sizeable downsides, though, because Martian air is extremely thin and primarily carbon dioxide, it’s extremely cold and Mars doesn’t have a magnetosphere. To terraform it, we’d need to artificially induce massive global warming, to re-build an atmosphere that works, and we’d need to somehow build a magnetosphere to maintain that now-optimized atmosphere. There have been various, theoretical suggestions made for the cold and atmosphere issues; from melting Mars’ polar ice caps by pointing giant mirrors at them, to Elon Musk’s proposal to strategically drop nuclear bombs on our planetary neighbour. As for the magnetosphere problem, that’s still a work in progress.

So, given the difficulties, why aren’t we looking at the planet that’s closest to us, instead? Perhaps we prefer to forget about Venus because in many ways it amounts to a genuine vision of hell. With boiling hot air and a chokingly thick, acidic atmosphere, it’s often nicknamed “Earth’s evil twin”. But, remarkably, thirty miles above Venus’ brutal surface, there is an environment that’s already similar to Earth. And NASA already has plans on how to live suspended in the sky, in the Venusian clouds. Called the High-Altitude Venus Operational Concept (or, HAVOC), it involves sending aeroshells to release enormous airships, to float in the dense atmosphere. In a bid to lessen the unbearable surface temperatures, there are also ideas to build a huge shield between Venus and the sun to cool it down, making its skies even safer. Considering that a trip to Venus could also take four months less than a journey to Mars, thanks to its closer proximity, the planet’s credentials mount up.

But we’re still straying further away from home than maybe we should. We’ve already been to the moon, so why not go back - but this time, to stay? It takes mere days to travel to, and it’s already in our solar system’s “Goldilocks” habitable zone. But there are also the moon’s extreme temperature fluctuations to deal with, from -170 degrees Celsius at night to +120 degrees during the day. It’s also still just a big ol’ rock incapable of creating and sustaining its own atmosphere. One ultra-ambitious plan to terraform the moon involves steering comets towards it and blowing them up just before they hit, so that their ice creates vast bodies of water. From there, we could cultivate algae, and begin to build an atmosphere. But, first of all, we have to invent the technology needed to achieve any of that. A simpler, more feasible idea is to build an enclosed, domed city at one of the moon’s poles, where the temperature shifts are less extreme. But we wouldn’t really be ‘terraforming’ anything at all this way, more just mounting a long-term logistical mission to ferry supplies between Earth and a moon base.

Of course, most of what we could even possibly achieve is determined by exactly how far we can travel. And, if we could find a way to fly further in a practical length of time, our options widen more and more. Jupiter really doesn’t seem like somewhere anyone would want to live. It’s an enormous gas giant very far from the sun, but scientists speculate that it might have a rocky core… And, that this still-incredibly massive core could contain similar element’s to Earth’s – like iron. If we somehow removed all the hydrogen and helium making up the “gas” part of the “giant”, we’d have a blank canvas to work on - planetarily speaking. It’s a pretty big “if”, though.

And, again, there could be a simpler solution; the gas giants’ moons. Jupiter’s Europa and Saturn’s Titan are widely held as two of the best locations for future human colonies, with more potential than even our own moon. With Europa, astronomers have observed regular water eruptions through the moon’s ice-covered surface, proving long-held theories that it has a subsurface ocean. These water geysers are enormous, reaching as high as 125 miles into space, and releasing massive amounts of hydrogen and oxygen. It’s why there’s increasing belief that Europa is the most likely place in the entire solar system to support alien life. With or without extra-terrestrials, though, it could well support us - if we can find a way to raise temperatures. From there, Jupiter’s other moons - including Ganymede and Io - would be next on our list of worlds to relocate to.

But perhaps we’d get to Titan first. For many, Saturn’s largest moon is actually our best bet for human colonisation anywhere in the solar system - despite the colossal distance between us and it. It’s big, it already has an atmosphere of its own, and it orbits Saturn outside of the planet’s famous rings - so we needn’t navigate those to get there. Like Europa Titan has a subsurface ocean, and it’s rich in valuable resources. We’d still need to significantly warm it up, maybe with those massive orbital mirrors currently theorised for Mars, but otherwise Titan could be a perfect match. By heating the surface ice we’d release hydrogen and oxygen, there’s already nitrogen on Titan, and the ice could hold plenty of ammonia, as well. Even better, because Titan has its own atmosphere, it’s not constantly under siege from deadly solar radiation - a problem for most other solar system places.

So, which world wins? We know most about Mars, but the Red Planet isn’t ideal for human settlement. Instead, there’s Venus - or at least its skies - which are closer than most other places, but we’d never be able to set foot on the surface. Then, there’s Titan - a far-off moon that’s currently impossible to fly to, but if we did ever get there (and if we could warm it up) then it has more potential than anywhere else. So, assuming we eventually work out how to reach it, that’s where we should terraform first.