> Just remember being in a "habitable zone" is but one, small necessary (and by itself absolutely insufficient) condition for actually being "habitable" or sust

> Just remember being in a "habitable zone" is but one, small necessary (and by itself absolutely insufficient) condition for actually being "habitable" or sustaining life. It's not even a necessary condition. The 'habitable zone' is based on the possible presence of water on the surface of the planet, which it is argued makes it more likely life could have evolved. But, it isn't a requirement, at least as we understand it. For example, Europa, a moon of Jupiter, is well outside the habitable zone but is believed to have a sub surface water ocean that could be capable of spawning life.