Ceres Low-Altitude Mapping Orbit (LAMO) |
Ceres Low-Altitude Mapping Orbit (LAMO) |
Dec 22 2015, 04:50 PM
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Senior Member Group: Members Posts: 3008 Joined: 30-October 04 Member No.: 105 |
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Feb 28 2016, 03:20 PM
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Considering the extensive emplacement of impact debris mantling units all over Ceres, I would guess the top 500 to 1,000 meters of the surface is a battered, crushed layer of poorly mixed, brecciated debris. There are quite likely a huge number of salt and salty ice deposits embedded within this debris layer.
When craters are made in this kind of surface, these pockets of high-albedo salt (or salty ice) become exposed; more are exposed as mass wasting deflates large crater walls. Thus, the occasional white spots and streaks seen in crater walls. Now, this is completely separate from directly-emplaced cryovolcanic deposits, like what we appear to see in Occator. Those (and there are quite a fewer number of them than the smaller white spots) seem to be examples of deeper material moving volcanically up to the surface from deeper layers of soft salty ice (or even liquid salty water). That's a different emplacement mechanism from most of the small bright spots we see on crater walls, I think. Think of it this way -- take a surface composed mostly of black sand, and randomly embed a bunch of white pebbles in it. Then hit it with an impact. Your resulting crater will show mostly black sand walls, but every once in a while a white pebble will poke out through the major black sand matrix of the unit. And as crater walls recede due to mass wasting, new white pebbles are exposed. Now, just replace the black sand with the general dark material of Ceres' surface and the white pebbles with concentrations of salt and/or salty ice, and you have a model for what may well be happening on Ceres. -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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