Goodbye Purgatory Dune!, Oppy on the move Options

[Tesheiner]

On the road again...

http://nasa.exploratorium.edu/mars/opportu...WEP1211L0M1.JPG

[Bill Harris]

Panorama wheeltracks at the rear of Opportunity at Purgatory Dune.

And we're already starting to get downwind tails from the recent wheeltracks. These are potentially active dunes!

--Bill

[Marcel]

And we're already starting to get downwind tails from the recent wheeltracks.  These are potentially active dunes!

--Bill

Only if the "pavement" is broken I'd say. Then the fines underneath are exposed and free to go. My feeling says that the winds on Mars don't carry enough energy to break apart the upper layer. I wonder for how long this situation has been that way. And (even more intersting to know): What process is responsible for this tough upper layer ? Liberation of chemically bond water by intense and long UV-exposure, on it's turn cementing together the minerals ?

[Bob Shaw]

Only if the "pavement" is broken I'd say. Then the fines underneath are exposed and free to go. My feeling says that the winds on Mars don't carry enough energy to break apart the upper layer.

Marcel:

Got to agree. I reckon these are really *old* dunes!

Which doesn't deny the possibility of salty sludge moving about here and there - we've seen surface frosts, and micro-climates may allow water flow in locations with appropriate solar heating etc (like, perhaps, some crater sides).

Bob Shaw

[sranderson]

It appears to me that Purgatory, and the tops of most dunes in general, have a pavement of somewhat smaller grains, spaced further apart, than the pavement between the dunes.