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FAQ - Astrobiology

1. With the discoveries of organisms using sulfur as a source of energy, can forms of life be out there that don’t depend on water?

As in all life forms found so far on Earth, the bacteria that use sulfur compounds in their metabolism still use water as the basic solvent (i.e. the fluid medium in which biochemicals are dissolved and thus allowed to interact). There have been speculations about other possible bio-solvents like ammonia, methane, or ethane. A good discussion can be found in Goldsmith & Owen (1993) "The Search for Life in the Universe", chapter 10: "How Strange Can Life Be?" Titan, the largest satellite of Saturn, has an atmosphere of nitrogen, methane, and ethane, and (presumably) lots of organic materials on the surface. Under these conditions, it has been speculated that ethane-based life might arise. There is an extensive article on Wikipedia:

2. If there could be life on other planets, which planets could or couldnt we live on?

We will leave out the gas giants because there are no surfaces for us to live on. If there is any life, it is likely to be below the surface of Mars or below the surfaces of several Jovian moons where liquid water might exist. In no case could we just go there and live: extremely thin atmosphere (or no atmospheres) and cold. Other than that, we could, with protection, live just about anywhere (probably not Venus). On Earth, we can live underwater, and we have people living on the Space Station where there is no atmosphere. So, we could live on the Moon (best to be underground to be protected from meteoroids and solar flares) and on Mars, but, again, only with protection and a way to supply ourselves for living there (air, food, water, and power).
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