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The uncertainty of science: The principal investigator of Dawn has indicated that the preliminary data they have gotten of Ceres’ white spots strongly suggests that they are not water but salt.
The mystery is far from completely solved, Russell cautioned. The team failed to get the quality of measurements they wanted in examining the spots, and they’ll have to try again at a closer orbit — like the next planned mapping orbit, which will take them from 2,700 miles over the surface to just 900. The photos taken at that height will also have significantly better resolution, which should further help the team determine what the spots are made of.
But based on the spectral data the team did get, Russell said, the spots “really don’t look like mounds of ice. … The bright spots are probably — like you might find in the desert on Earth — a salt plain where maybe water came out at one time and evaporated,” Russell said.
None of this is confirmed, and won’t be until they lower Dawn’s orbit to get higher resolution images. However, this must wait because they have extended Dawn’s mapping orbit for now as they review the issue that caused the safe mode incident on June 30.