[X] My Assistant

[SigurRosFan]

http://www.msss.com/mars_images/moc/2005/10/24/

cPROTO Oppy:

[Guest_Edward Schmitz_*]

The ground truth that we have from the rovers tells us that the dunes are evolving too slowly to see any motion from orbit. At best (with current res), we would have to wait upwards of a century to see anything. Probably longer...

[dvandorn]

The ground truth that we have from the rovers tells us that the dunes are evolving too slowly to see any motion from orbit.  At best (with current res), we would have to wait upwards of a century to see anything.  Probably longer...

I disagree. The ground truth shows that disturbed martian soil at Meridiani (as in disturbed by the MER tracks) starts blowing around after only a day or two. And it shows that the drift surfaces are not cemented.

The only thing that keeps the drifts from changing dramatically from day to day is an equilibrium that has evolved between the grain sizes and the winds' transport capacities. Change that equilibrium (for example, by adding a few tons of dust per square kilometer, say in a dust storm), and I'd bet the drifts will evolve much faster and more noticeably.

Of course, if this dust storm kills Oppy, it'll be sort of hard to show how the greater levels of deposition will affect the drifts...

-the other Doug

[Marcel]

The only thing that keeps the drifts from changing dramatically from day to day is an equilibrium that has evolved between the grain sizes and the winds' transport capacities. 
-the other Doug

Exactly. BUT: why should adding some dust to the surface change this ? The dunes are the dunes and adding more dust cannot alter the original dunes underneath that easy. The dust can accumulate on them, but it will be blown away more easy than the material of the dunes itself. Just like the only transportation of material we actually saw happening was the change in oppy's tracks. But this was in an unnatural (non Mars induced) circumstance: by crunching the topsoil that is "stripped" from its "finest fines" by eons of wind, fines from underneath are liberated and go there way immediately. To my point of view, that's what we saw happening within day's, but that's about it. We did not see ANY movement, not even with MI, considering the untouched surface.

I think these dunes are altered and formed in highly rare happenings of major windspeeds. And i think it took an unbelievable long time to form.

Besides: there's not a single reason why observations from orbit could add new insights about these processes....because not even Oppy sees it moving from a million times closer than any orbiter......