12 There is water everywhere

Water was once considered rare in space. But water ice exists all over the Solar System. It’s a common component of comets and asteroids. Water can be found as ice in permanently shadowed craters on Mercury and the Moon, though we don’t know if there’s enough to support prospective human colonies in those places. Mars also has ice at its poles, in frost and likely below the surface dust. Even smaller bodies in the Solar System have ice: Saturn’s moon Enceladus and the dwarf planet Ceres, among others.

Scientists suspect Jupiter’s moon Europa may be the most likely candidate for extraterrestrial life because against all expectations there’s likely liquid water below its cracked and frozen surface. Europa, much smaller than Earth, may host a deep ocean that researchers suggest could contain twice as much water as all of Earth’s oceans combined.

But we know that not all ice is the same. A close-up examination of Comet 67P by the European Space Agency’s Rosetta spacecraft revealed a different kind of water ice than the kind found on Earth.