Theres an interesting picture here 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.

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

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

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).