An ocean may once have covered much of Ceres, the largest body in the asteroid belt. And much of that ocean may still be there. It doesn’t pool on the surface, though. Instead, some of its water may have mixed with rock and minerals to make up Ceres’ crust. And some may lie below the surface — perhaps in liquid form, or mixed with other materials.
Ceres is about 600 miles in diameter — roughly a quarter the size of the Moon. It’s been studied in detail by Dawn, a spacecraft that’s been orbiting Ceres for the last three years. Dawn has revealed a surface that’s covered by craters. Bright white features highlight the floors of some of the craters — possible salts from an underground ocean.
Dawn’s observations have shown that the rims of some of the craters, as well as the only tall mountain on Ceres, have “slumped” over the eons — they’re not as tall and sharp as they once were. Yet the little world’s crust should be quite rigid. It’s made of frozen water — possible remnants of an ancient ocean — mixed with other ices, salts, and solid rock — a composition that should allow surface features to hold their shape.
That suggests that there’s a “squishy” layer below the crust. It could be partially liquid — water from the ancient ocean mixed with rock and ice. That would have enough “give” to allow the surface features to slump — reshaping a surface that might once have held an ocean.
We’ll talk about water on another world tomorrow.
Script by Damond Benningfield