Some of the startlingly bright terrain on Ceres' heavily cratered surface.
NASA's Dawn mission has achieved a number of firsts, including being the first spacecraft to go into orbit around two different bodies. The second of those destinations is Ceres, a dwarf planet that is by far the largest body in the asteroid belt. That visit has now shown us that a lot of our expectations for what we would find at Ceres were wrong: it's not an icy body, but liquid water has helped shape the dwarf planet's most dramatic features.
A couple of papers that analyze Dawn data have appeared in Nature journals this week. In one case, they suggest that the dwarf planet's composition is much rockier than we expected. But the other suggests that the mysterious bright spots found in some of Ceres' craters are the result of salty brines making their way to the surface.
Our thoughts about Ceres prior to Dawn's visit were dominated by the dwarf planet's relatively low density. This suggested to many people that it must be composed largely of water, although the surface was darker than you would expect from water ice that was expected to be a thin veneer over an icy world. Craters were also expected to be relatively scarce, as water ice is semi-viscous at the temperatures (120K and up) expected to be found on Ceres.
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