Dawn probe to look for a habitable ocean on Ceres

摘要

Ceres, the largest object in the asteroid belt, isn't an asteroid. It's not a planet, either; since 2006, this ball of rock and ice some 950 kilometers in diameter has been classed as a dwarf planet, like Pluto. But it is a member of an even more exclusive club: the short list of solar system bodies that may have once been habitable.