Here's another shot of Oppy's IDD on Sol 505, this time against her right wheel. Attached because an inline image would be pretty large on the page.

For raw images, you could just post a link rather than attach it... it might be good to save space on Doug's servers.

I've also been concerned about Oppy's progress recently. Squyres' update explains a lot, though. I hope we'll be rolling again soon.

Mega-kudos once again to Steve Squyres for doing these updates.

Anyway, MI images are pretty interesting, especially the lower one, which should be taken in the "untouched zone" (based on the time of Hazcam picture) but show some collapsed BB... (natural or did MI inadvertitely pushed them?):

Found answer:
stitching toghether the four MI images, collapsed region has clear circular shape, so should be due to Oppy pressure (probably done with Mossbauer spectrometer...); maybe also deliberated in order to test how sand is soft! :

I second that - there's the large outer circle, and then there's a smaller, untouched circle in the center.

Comments about the picture, This terrain has a mix of two types of sand, fine and blueberries.

I don't see any other strange things except to fine sand and Blueberries. Almost pure. No other mixing. No vegetation or marine residues from the old times as it is supposed that Meridiani Terrain was a sea.

Rodolfo

Well that what you would expect, here on Earth you can find seashells and wooden twigs on a beach because they are very recent. In less than a hundred years they will be grided down to sand or dust. White beaches often are made of the former, broken shells from sea living organisms.

If either kind of life ever have been found on Mars, the remnants would be long gone, sandblasted over hundred of millions of years. Fossils in bedrock can be preserved even then, but that takes a dedicated geologist human or robotic with tools to cut rock.

Yet the very low amount of organic material on the Martian surface make me wonder if the planet even could have had single cell life.
When I was a child, it was one almost universal belief that the planet had some kind of vegetation due to the changing appearance over the seasons seen from earth bound telescopes.
We know the truth now, but I still think Mars are one fantastically interesting place.

Better, perhaps to show images from the same angle:

Navcam sol 465

Navcam Sol 484

I can't say I see much difference here.

Me neither, what are we supposed to see that's different ?

MahFL you might have another look at the pan cam L2 - sol 496 image.
No comparision needed, in the wheeltracks you can see signs that the wind have been at work, its not dramatic, but its obviously there. I would rather say that is about what to be expected. Remember that this is Mars with an atmosphere of perhaps just 6-8 millibar. On Earth you could of course see a bigger change in a single day if it was a bit windy.

I can see a small difference. The difference is that the edge of older track is more rounded than the new one.


Rodolfo

Ok, I thought it was obvious but...

pan cam l2 - sol 496

Look carefully just below the center of the frame. There are stream lined little islands of dust with a blue berry at head. Wind tails! The wind direction is blowing cross frame and slightly away. The evidence is all over the frame. Take a look at the top track. There are tendrils of dark matterial streching across the track. They also cross multiple treads. And don't appear in the earlier shot. They would appear to be minor ripples that are marching along. Compare the treads between the earlier shot and this one. Or even the top track's treads and the bottom track. They are filling in and eroding away.

This, too me, is evidence that the dunes are currently active. So it is not a matter of how old are the dunes, but how fast are they changing.

Sorry for being too vague in my earlier post.

ed

You have well and truely convinced me. The amount of change is more than I would have expected given the low pressure. This movement of the very fine particle also implies continual sand (dust) blasting and erosion of the surface blueberries and it follows that they must be right through the dunes.

I don't see how the blueberries could have come from anywhere else than where they currently lie and therefore the dunes are composed of material weathered from the underlying rock rather than blown in from elsewhere. What process could then be responsible for the removal of the salt portion of the underlying rock to leave this surface blanket. It can't be wind erosion since none of the bedrock here is exposed to the wind.

Could it be just simple diurnal temperature cycling over millions of years. The range is 100+ deg. How far down would you have to go to get a stable temp, 1/2m? 1m? that is just about the thickness of the dune material?

Sorry RNeuhaus I wasnt referring at any rounding at all in the the pan cam L2 - sol 496 image but the streaks with a pebble at the front end and semi-circles.
So Edward Schmitz are correct and we both happened to look at the same thing, it was the 'darker material' and 'streaks' I was referring to.

Another panorama of an Mossbauer imprint in the wheeltrack of Opportunity at Purgatory Dune.

Taken with the MSI Cam on sol 507.

jvandriel

That's impressive- thanks for pointing out the changes. I'm not sure this is evidence for active dunes, though. The tops of the dunes are armored by a layer of blueberries and/or other coarse debris. Oppy's wheels have disturbed that armor, exposing fine dust which is then easily picked up and moved by the wind. The dunes themselves may not move unless the wind is strong enough to disturb the armor or somehow pick up grains from beneath it.

Mossbauer intrument made some pressure inside the right track (Sol 507) :

Incredible fine sand like a powder. It looks that the sand has somewhat humidity because of the presence of cracks. Who else can tell more about this?

Rodolfo

A fine enough powder acts like this in the complete absence of moisture -- in fact, moisture keeps a fine powder from acting this way. Try pressing some flour down onto a plate and see what it looks like... you'll get cracks like this.

-the other Doug

Thing is though, a dry day on Earth would probably be outright dank and humid for Mars. This is low grav, low air pressure powder here.

Yes, but an average day on Mars would be considered tremendously dank and humid (and air-filled) on the Moon, and you see lunar dust forming cracks like this, too. In the complete absence of air and water.

It has to do with the grain size and morphology -- fine powders become somewhat self-cohesive, especially in a vacuum or under low pressure. That's what causes the cracking action. As I said, it even works in our own atmosphere with most fine powders.

-the other Doug

I agree with you since I have ever observed the powder behavior. The powder has somewhat static attraction property that unites among powders.

Rodolfo