Saturday, October 01, 2016

Dawn Finds Ceres Craters Where Water Ice Accumulates

Dawn Finds Ceres Craters Where Water Ice Accumulates

NASA/Jet Propulsion Laboratory

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NASA’s Dawn mission has revealed permanently shadowed regions on the dwarf planet Ceres, which could be cold enough to trap water ice for a billion years. As suggested by the study published on July 11 in the journal Geophysical Research Letters, this could mean that ice deposits are still present in these regions.

“The conditions on Ceres are right for accumulating deposits of water ice,” adds researcher Norbert Schorghofer, a guest investigator from the University of Hawaii at Manoa. “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.”

No one actually knew whether Ceres has cold traps until now. The team explains that the shadowed regions are located on the crater floor or an area of the crater wall that faces the north pole and do not receive direct sunlight. When the regions get as cold as minus 151 degrees Celsius, they become cold traps that get filled with water ice.

Since only one out of every 1,000 water molecules generated on the surface of Ceres end up in these traps during a year on the planet (1,682 days), it would take the water 100,000 years or more just to become thin ice deposits.

The study involved using images taken by Dawn’s cameras. The data, including craters, the dwarf planet’s shape and plans were turned into a computer model.

The largest shadowed region is estimated to be as wide as 16 kilometers or 10 miles. This is located less than 65 kilometers or 40 miles from the planet’s north pole.

Overall, the dwarf planet’s shadowed regions cover about 1,800 square kilometers or 695 square miles, occupying less than one percent of the northern hemisphere. The researchers believe that the shadowed regions on Ceres are colder and could have been formed from a larger reservoir of water than the ones found on Mercury or .our moon

However, Ceres’ shadowed regions resemble more of the regions found on Mercury than the moon. Like in Ceres, the shadowed regions also occupy nearly one percent of Mercury’s northern hemisphere. Nevertheless, both of the planet’s shadowed regions have similar trapping efficiency.