[X] My Assistant

[Ant103]

The view toward Beagle is more and more precise.
http://origin.mars5.jpl.nasa.gov/gallery/a...CNP2435R2M1.JPG
The crater place seems to be a bit complex.

[chris]

Looks like lots of chunks lying around. Its going to be very interesting to see how they have interacted with the sand du, er ripples. Which leads me to another thought...

There have been lots of discussions on the tiny craters, etc, and whether they are caused by sapping or are tiny impact craters. I've been puzzling over this for ages (I'm not a geologist, btw). It seems to me that the dunes must be static now, otherwise the wind that we know blows over the plains would fill in the craters by moving the sand. They must have been mobile at some point, otherwise they wouldn't have the wind-sculpted shapes. This means they *must* have been mobile at one point.

I'm finding it hard to understand how slow hardening could result in preservation of the ripple shapes, so it ocurred to me that it might not have been so slow. We know that the apron of Victoria is splash-like, which might imply water. So perhaps the impact released a cloud of water vapour that interacted with the very fine, very dry sand, and essentially fixed it in place.

Am I talking nonsense?

Chris

[Bill Harris]

Doug, I'll agree with you wholeheartedly that these dunes are active and not a frozen-in-time museum piece. As seen, and as you note, by the changes observed in the Rover's tracks, deposition on the Rovers and other features we have observed along the way. Slow by Terran standards, but far from dead.

Even light force will act given enough time. If you hit a piece of glass with a hammer, it will shatter. If you stand a piece of glass against the wall, over centuries it will flow as a supercooled liquid in respose to gravity.

Even though I'm a geologist and accustomed to thinking in aeons, I have great trouble visualizing timeframes of millions of years for some of these minor processes. The little intuitive voice in the back of my head suggests hundreds or thousands of years, give-or-take.

We're on the right track, though.

--Bill

[dvandorn]

Even light force will act given enough time. If you hit a piece of glass with a hammer, it will shatter. If you stand a piece of glass against the wall, over centuries it will flow as a supercooled liquid in respose to gravity.

Getting into this a little late, but... guys, think of the hard basalts and other lavas we've seen at the other landing sites, that have been carved and polished by the winds over the aeons into perfectly smooth surfaces. If y'all have ever seen chunks of this kind of rock, you'll note that in its more natirual state it doesn't feature such nice, gently curved, smooth surfaces.

These ventifacts, which are ubiquitous wherever you find hard rock, are even more compelling mute testimony to the powerful, if slow, erosive force of the Martian winds than are the ripples/dunes.

-the other Doug