What do experts believe are the minimum requirements for life elsewhere?
For carbon-based life, the minimum requirements are probably liquid water, organic chemicals and some kind of energy source for metabolism. As organic chemicals and energy sources are relatively common, the crucial ingredient for a habitable world is liquid water. But more exotic life forms might inhabit very different environments: an alternative kind of carbon biochemistry might work without water, perhaps using ammonia as a solvent; silicon might form the basis of high-temperature creatures; and even stranger life forms have been imagined existing within interstellar clouds or on the surface of neutron stars. But for now most astrobiologists are concentrating on carbon-and-water life, which we know is possible.
