[X] My Assistant

[akuo]

Oppy looks like to be stuck in a dune once more!

The front wheels (rover was moving backwards into the dune) look to be closer to solid surface than during the purgatory incident, so hopefully they can back out pretty quickly.

I know this is already being discussed in the other thread, but I think this way the incident is clearer to a casual reader of the forum. Threads of nearly 1000 posts clog the discussion anyway.

http://qt.exploratorium.edu/mars/opportuni...GBP1151R0M1.JPG

http://qt.exploratorium.edu/mars/opportuni...GBP1311R0M1.JPG

inline images changed to links. 2048 x 1024 of images clogs discussions as well - Doug

[WindyT]

While I well buy into the hypothesis that older, filled in small craters might lend themselves to being filled with less compacted "soil", I'd like to propose a thought that there were dune building stages, and that at least one of the later stages deposited material that hasn't compacted well... or well enough, in the case of Opportunity. I read the abstract that was recently linked to off of this forum suggesting the current winds are less than half of what created most of the dunes -- I'm not a dune morphology expert, but could a different set of winds, represented by those transverse dunes we're now seeing more of, move some of the material in such a fashion that it hasn't had the time(?)/conditions to compact to the same level as the more compacted dune material? Perhaps move more of a particular source contributing material, one with a higher percentage of material that doesn't compact quite so much?

Or is it just a coincidence that this latest "sandtrap" occurred on the lee side of one of the transverse dunes? Obviously the transverse dunes weren't apparent in the earlier "sandtrap" events for Opportunity, but that doesn't negate the possibility that lenses of the lesser compacted material may have been shaped by wind "regimes" taking place over time.

If so, I would also propose a final "scattering winds" event that covers the surface difference between various dune making events, hiding the transitions from the cameras on Opportunity.

An alternative theory would be for lenses of evaporite ejecta (not so much "vaporized" as "pulverized by the time it lands") covered by a light coating of dune material, where that pulverized stuff never would compact properly for whatever reason. This I would think would be more easily proven or disproven, and I don't lend credence to this "pulverized evaporite that never got a chance to compact" line of thinking, but realize it's also an idea that might be thought through.

And all of this pre-supposes that there are measurable differences between the compaction rates of dune material, and not merely just Opportunity breaking through when turning.