Study: Ceres Likely Harbors Water Ice in Polar Craters

Blue areas represent zones of permanent shadow
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A paper published in Geophysical Research Letters concludes that in addition to whatever ice reserves the dwarf planet Ceres may harbor under its surface, (and they could be substantial, including even a subsurface ocean) the largest body in the main asteroid belt has also likely accumulated quite a bit of water ice in permanently shadowed areas of craters near its poles.

Abstract:

“Ceres has only a small spin axis tilt (4°), and craters near its rotational poles can experience permanent shadow and trap volatiles, as is the case on Mercury and on Earth’s Moon. Topography derived from stereo imaging by the Dawn spacecraft is used to calculate direct solar irradiance that defines the extent of the permanently shadowed regions (PSRs). In the northern polar region, PSRs cover ∼1800 km² or 0.13% of the hemisphere, and most of the PSRs are cold enough to trap water ice over geological time periods. Based on modeling of the water exosphere, water molecules seasonally reside around the winter pole and ultimately an estimated 0.14% of molecules get trapped. Even for the lowest estimates of the amount of available water, this predicts accumulation rates in excess of loss rates, and hence, there should be fresh ice deposits in the cold traps.”

NASA recently extended the Dawn spacecraft’s mission at Ceres, electing to keep it in place there, studying the fascinating mini-planet, rather than pursue an alternate proposal to have it break orbit and fire up its ion drive to proceed to what would have been its third destination following an initial visit to the asteroid Vesta and then Ceres.