Planet Ceres' ice-friendly craters mapped

NASA's Dawn probe has identified shadowed regions on the dwarf planet Ceres, where ice can accumulate.

Guest investigator Norbert Schorghofer of the University of Hawaii said, "The conditions on Ceres are right for accumulating deposits of water ice. Ceres has just enough mass to hold on to water molecules and the permanently shadowed regions we identified are extremely cold - colder than most that exist on the moon or Mercury."

Permanently shadowed regions do not receive direct sunlight and are typically located on the crater floor or along a section of the crater wall facing toward the pole. The area is a cold trap - a good place for water ice to accumulate and remain stable. Cold traps were predicted for Ceres but had not been identified until now.

In this study, Schorghofer and colleagues studied Ceres' northern hemisphere, which was better illuminated than the south. Images from Dawn's cameras were combined to yield the dwarf planet's shape, showing craters, plains and other features in three dimensions. Using this input, a sophisticated computer model developed at NASA's Goddard Space Flight Center, Greenbelt, Maryland, was used to determine which areas receive direct sunlight, how much solar radiation reaches the surface, and how the conditions change over the course of a year on Ceres.

The researchers found dozens of sizeable permanently shadowed regions across the northern hemisphere. The largest one is inside a 10-mile-wide (16-kilometer) crater located less than 40 miles (65 kilometers) from the north pole.

"While cold traps may provide surface deposits of water ice as have been seen at the moon and Mercury, Ceres may have been formed with a relatively greater reservoir of water," said principal investigator Chris Russell of the University of California, adding "Some observations indicate Ceres may be a volatile-rich world that is not dependent on current-day external sources."

The study appears online in the journal Geophysical Research Letters.