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Posted by: marsbug May 16 2008, 01:34 PM

Theres an interesting picture http://www.universetoday.com/2008/05/16/unusual-crater-in-mars-mamers-valles-gallery/#more-14320 of a crater with a strange dark patch at one end, would anyone care to hazard an explanation? I thought it could be an exposed section of basalt, but I dont see why it wouldn't be covered with dust like the rest of the terrain.

Posted by: Juramike May 16 2008, 03:23 PM

Very cool.

I'd speculate that the crater is actively sinking (especially the deeper section off center to the E (lower section in the image)). Could the dark deposits be mineral salts left behind by sublimating ice?

-Mike

Posted by: dburt May 17 2008, 01:23 AM

Mike - Another possiblility might be dark basaltic wind-blown sand. Spectral data (e.g., from CRISM) should be able to answer the question.

-- HDP Don

Posted by: SickNick Jun 8 2008, 02:30 PM

That blue-black stuff has always turned out to be dust when investigatigated. Usually basaltic, often olivine-rich, but just dry windblown (or windlagged) dust...

If you look in detail at the albedo vs elevation, you'll see "sheltering" effects in the lee of bumps on the crater floor. The "south" (down) of any lump has more dust than the "north" (up).