Yeeha! What a ride. And other good new: Exploratoruim seems to be unclogged and posting images.

--Bill

Yes, looks like Exploratorium is unclogged, thankfully. I like this MMB "top view" from Sol 580:

That was quite a nice ride Bill, especially after standing in line with a purchased ticket all weekend long. When the images showed up earlier today, I couldn't wait to get home from work to post the "X marks the spot" comment, but Burmese clearly beat me to it.

This highway is a really interesting place. I'm hoping this is just an introduction to the etched terrain. Looking at it in 3D, it really doesn't resemble the Autobahn, but rather a rough road. I hope we find even more vertical relief as Opportunity heads onward.

We really should thank that Exploratorium webmeister for keeping the traffic flowing on the other highway.

I'm going to try to rephrase my question on this point of interest to me: take the small dune that is just to the upper left of the rover in the MMB composite that is in the post I'm replying to. Has that dune been in the same place, little changed, for decades or centuries? Or do these dunes creep across the bedrock over a shorter time scale, sometimes hiding and sometimes exposing them?

I think the best reply to that is "we don't know." We've seen that rover tracks get partially filled in over the course of only a few months, so this cannot be a static scene. But we don't know, with enough certainty, the entire range of particle sizes of the particles that make up the drifts, and we don't know what the average and "special" rates of airborne particulate volume are. Finally, we don't seem to have really good models for how sand and dust particles move and flow over and around aerodynamic obstacles in the Martian atmosphere, and in the roughly 1/3G gravity of Mars.

My best guess is that these drifts evolve and change over fairly short time scales (tens of years), but that the whole system is near to a sort of static balance. It's not a closed system, since material is constantly being both removed and added from the local scene (the evaporite is slowly eroding and windborne dust is slowly being deposited). But I'd bet that these drifts are constantly being formed, deflated and re-formed in roughly the same sizes and orientations as time goes on.

So, specifically, any given drift you see on the ground right now may not have been there 10 or 20 years ago, but the overall scene looked very, very much the same as it does right now. And has for perhaps a billion years or more.

-the other Doug

other Doug:

*Have* we? Or have we simply seen loosly adhering structures gently fail after being freshly exposed?

Are the mechanics of MER tracks comparable to pre-existing dune surfaces?

If we see dune material moving, then that's one thing - seeing disturbed tracks collapsing is quite another! I'm still not convinced that the dunes, in general, move in anything like a human timescale (though one picture could change my mind).

Bob Shaw

Best would be two+ pictures taken a known time apart.

Best of all, we already have them.

We have some photos of the Erebus highway from orbit (taken when? Weeks, months ago?) and can tie it in with the situation on the ground today. I think the match has been pretty good, so far, given the difference in resolutions. No "movements of metres" that I can see, I think?

I'd agree with you, Bob - in the absence of anything like an active hydrological cycle, the aerolian shifts are slow, perhaps cataclysmic in nature (requiring a global dust storm or similar) and result in very, v-e-r-y slow rates of change.

Andy

My understanding is that Oppy's tracks outside of Endurance had been almost completely obscured and filled in during the six months that Oppy spent inside the crater. It wasn't a matter of side dirt infalling -- the entire set of tracks simply disappeared at points, and were obviously degraded and filled in where they were still visible.

Of course, I didn't go walking around Endurance checking this out -- I got this from comments made on this board and by MER team members in the media. But from the images I saw, it appeared to be a valid observation.

-the other Doug

other Doug:

Tracks don't count, as they no longer represent pristine surfaces! The material which has been exposed may well collapse after being compacted by the wheels, but that's not really evidence for what the normal surface gets up to.

I'm open-minded, but not willing to compare chalk with cheese!

Bob Shaw

True, Bob -- but we're not comparing the pristine surface to a concrete roadway planted on top of it. If tracks are getting filled in, it's more than likely that the remaining landscape is being affected by the same forces, too. And if the tracks are being completely obscured in a matter of months, I'd say it's well-nigh impossible that the scene we see around us is static and unchanging over thousands of years, much less millions.

-the other Doug

I'm pretty much convinced that the scenery we see is constantly changing dramatically over decades and thus is an active dune(ripple)field. The rapid filling of the tracks almost prooves this. This is coming from elsewhere, not just collapsing track"walls" and so it also settles down outside the tracks. Just as it's removed from there as well. There's no reason whatsoever to state that the deposition inside the tracks is completely different from locations elsewehere.
There might be a slight difference because the tracks are depressed and catch dust more easily than the untouched plain. But it can't be THAT different.

Wonderful vertical projection, Michael.

The Erebus Highway doe not look like an Autobahn, but more resembles and ancient Roman road, hence my earlier appellation "Via Meridiani". In the MBB vertical, the fabric of the Burns (evaporite) Formation is clearly visible and it looks like classic stress-strain jointing. This is tectonics in action, but where does the compressive force come from? I don't see shock from cratering causing this.

Come to think of it, the first thing we learn about cratering on Earth is to look for shatter cones and shocked minerals (quartz). Have we seen anything resembling sashtter cones here? I think not.

Like oDoug, I think that changes in the drifts are on the decade timescales. Not yearly as on Earth and not over millenia as on the Moon; we haven't looked long enough to see things. Yet. I alos think that the wind is more of a player than we suspect; although thin, it can pack a lot of punch at 200-300 mph.

I'n getting giddy here, too. Homeplate is bad enough...

--Bill

Hope that with the HiRISE (High Resolution Imaging Science Experiment) of MRO will testify it. Wait until after November 2006

Rodolfo

Talking of pristine highways... this one definitely needs regrading. The attached cross-eyed stereo view shows just how lumpy this rock field is...