There may be as many as 100 million habitable worlds in the Milky Way. But just what, exactly, are the requirements for life? And what are the environmental extremes that life can handle? A new checklist for the habitability of exoplanets attempts to answer these questions.
In the December issue of New Space, planetary scientist Christopher McKay rallies for a permanent, inhabited NASA research base on the Moon. National Geographic has distilled McKay's argument into a six-point list. Complement with io9's 185-point argument for a NASA lunar base.