If you've followed along on this blog -- or if you've followed the NASA Dawn mission -- you'll know that one of the great mysteries of Ceres the Asteroid was what the big bright white spots in Occator Crater, which were visible a huge distance away from the asteroid, were made of.
The white spots in the crater are shown below.
Well, the answer is definitively that they are made of slushy salts. That might not sound so remarkable, except for the fact that they are on a small planetary body that should actually be bone dry -- and this small planetary body apparently has subsurface salty water.
Which is quite remarkable.
So here's the story, straight from NASA:
Mystery Solved: Bright Areas on Ceres Come From Salty Water Below
"On Ceres' surface, salts bearing water quickly dehydrate, within hundreds of years. But Dawn's measurements show they still have water, so the fluids must have reached the surface very recently. This is evidence both for the presence of liquid below the region of Occator Crater and ongoing transfer of material from the deep interior to the surface.
The scientists found two main pathways that allow liquids to reach the surface. "For the large deposit at Cerealia Facula, the bulk of the salts were supplied from a slushy area just beneath the surface that was melted by the heat of the impact that formed the crater about 20 million years ago," said Dawn Principal Investigator Carol Raymond. "The impact heat subsided after a few million years; however, the impact also created large fractures that could reach the deep, long-lived reservoir, allowing brine to continue percolating to the surface."
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