Part of the show Crowd Control, Football Hooligans and Singing Mosquitoes
Mike in Rhode Island asked:
Life on Earth uses energy either directly or indirectly from the sun. However there are deep sea organisms that live off the energy that pour off from hydrothermal vents and don't receive any energy from the sun. Is it possible for a planet to have enough geothermal activity to sustain a robust ecosystem without receiving any energy from a star?
People were quite interested in a couple of moons around other planets, for instance, Titan. This is because it has a very large store of organic molecules. Because it's near Saturn, which has a very strong magnetic field, it has the ability to bend and stretch Titan. The strong compression and expansion creates a lot of heat and people think that this might be sufficient to cause water to exist in liquid form in those liquid worlds and they therefore might be a good spawning ground for life. The thing about the hydrothermal vents on Earth is that the life you find there all evolved originally from bacteria that depended on the sun's energy. They then became specialised, rather than being a brand new form of life that just appeared there, which is ever so subtly different. It's perfectly plausible that it might happen on another planet though.