Living on Rogue Planets

Most planets are gravity-bound to a star. But there are many that are not. Known as rogue planets, or free-floating planets, they inhabit the region's between the stars, bound only to the gravity of the galaxy as a whole. Such worlds are dark and cold, and it would seem at first thought that they would be unsuitable as a destination for colonisation.

But indigenous life could evolve even there, which means that humans could survive there, too.

A rogue, or free-floating, planet with a small moon

Rogue planets could be of any type, from gas giants to small Earth-sized world's of Rock and ice, and it would be those smaller planets that would be of most interest. If a thick enough layer of water ice were present, a subsurface ocean, like those found on some of the moon's of Jupiter and Saturn, would be a strong possibility, kept warm by geothermal vents in the rocky core. The nutrients flushed out could provide a stable environment suitable for simple life to form. And it could provide an environment to sustain and feed a human colony.

A view of a nebula from the surface of a rogue planet

Another type of rogue world, blanketed in a thick hydrogen atmosphere, could also be suitable for colonisation. In such a cold environment such an atmosphere could be sustained on a relatively small rocky planet, and the insulating effect of the gas would keep the surface temperature above the freezing point of water. This would allow lakes and oceans to form. If the planet remained in this state for long enough it is entirely possible for life to evolve, once again fed by the nutrients of volcanic activity from the core.

Of course, such a thick atmosphere would create surface pressures that would be difficult for human colonists to deal with, and the perpetual darkness would present it's own issues. Power generation would need to nuclear, and eventually geothermal. There would be psychological issues, too. Humans evolved in a sun-drenched environment. Such an environment could be simulated, though, and the experience would be no different to that experienced on a generation ship on its centuries-long voyage between stars.

Colonists arrive on a hydrogen 'blanketed' rogue planet

Now that we've established that colonisation is possible on such worlds,  another question arises: why would we want to do it? Such dark, cold and remote planets seem to offer little that is desirable as a place to live. They seem positively undesirable.

But when we consider them with regards to the survival of our species such remoteness becomes highly desirable indeed. And this is why:

• Rogue planets are generally a light-year or more away from the nearest stars, greatly reducing the chances of being hit by lethal solar events.
• Without the debris of rock and ice associated with solar systems, the risk of a catastrophic impact is almost completely removed.
• An advanced and predatory extra-terrestrial civilisation is more likely to overlook, or even not notice, such planets, offering humans a higher chance of surviving should such a civilisation ever become aware of our existence on Earth.

Intelligent extra-terrestrials examining data on their latest discovery: Earth...

Transporting a colony to a rogue planet is the main hurdle to overcome. It would be hard to justify sending a large ship of colonists that would then have to decelerate deep in interstellar space and become trapped in the gravity well of such a planet. But when large generation ships do eventually leave to colonise worlds around other stars, it would be relatively easy to incorporate smaller ships into the design that would be despatched enroute. With just a couple of hundred carefully chosen occupants a viable colony could be established.

Such colonies, as hard as they probably would be to build, may well become the most sustainable and successful, having overcome some of the most extreme challenges possible.

Indeed, such colonies, and the skills that they would learn, may well be the only way to ensure the continuation of our species beyond the general heat death of the universe.