Ruminating about the fates of these lonely, lost worlds, Stevenson has concluded some of them could actually be cozy, if pitch-black, homes of alien life. It's just an idea. And it's fun. Stevenson reports on his fun idea in today's issue of the journal Nature. Planets coalesce from the disk of dust and gas left over after the birth of a star.
Small clumps clump into larger clumps.
But the gravitational tugging between planets and mini-planets likely swung many of them straight out of the neighborhood, like pebbles flying out of a slingshot. The difference between Stevenson's hypothetical exiled worlds and the frozen wasteland that Earth would be in interstellar space lies in the atmospheres. Moving through clouds of hydrogen gas, Stevenson surmises the wandering planets could accumulate a dense blanket of hydrogen on the way out. In the oceans, life could arise near geothermal vents, similar to creatures found on Earth's ocean floors. Still, the available energy would be about 5,000 times less than that on Earth.