[X] My Assistant

[fredk]

In this new pancam view you can see some of the bright scraped rocks that Spirit made while driving around sol 1350-ish, at the far end of HP slightly right of centre.

[Shaka]

Wow, Freddo, they're like heliographs! I wonder if there are similar rocks over on this side. I have seen some bright scratches on the local rocks (e.g.Scratched Northside Rocks ), but not the same flaring that is down to the southwest. I wonder if we'll ever learn the cause of their albedo.
Have we forever left the surface of Home Plate?

[alan]

What are stamps and how do I view them?

If you click on table of images from all sols it will list the sequences that have been downloaded, the most recent first. Click the stop on you browser after it reaches the sol your interested in so you don't download the entire list. Click the link for the sequence your interested in, the links start with a p. It will give you a list of the files from that sequence along with 200x200 images, although sometimes you get 'cannot find image'

[Ant103]

http://marsrovers.jpl.nasa.gov/gallery/pre.../20080103a.html

[Cugel]

Then you have a very atypical definition of "erosion" that you are using.
...
I could go on and on about all of the erosion processes on Earth that are real and observable on a timescale of a few months, but you get the idea.

Yeah, I get the idea! And I appreciate the input. (from HDP Don also) For me as a non-geologist erosion is the sum of all processes that turn mountains into plains. Forces that really shape the surface of a planet, so to speak. As for that 3 month period on Earth, I was clearly wrong in how I formulated that statement. On the other hand, catastrophic events like mountainsides sliding in the ocean are so rare... to me that looks more like the macro result of an erosion process than the process itself that probably operates on a micro scale. The example of a car parked in the Mojave dessert and being sprayed by dust is nice because it relates well to Spirit's situation on Mars. And I accept that this is an erosion process that is detectable over a few months.

So my question would be, when wind moves a dust ripple (or dune, or just a few grains) from A to B, would a geologist call this erosion?
My (clearly non-geologist) opinion is that this is a local change (proving that Mars is a pretty active planet in that respect) but not erosion, mainly because it is a reversible event. On a small scale the ripples move around but on a larger scale the Columbia Hills don't change. Except maybe for 0.01 nm per year.

[djellison]

We don't really need to debate the semantics on this one.

I don't believe this is erosion. The tracks are actually still there, just covered up with dust.

That was the point you were making. This wasn't a debate about the erosion of rocks, hills, and mountains. This was about the disappearance of tracks on the ground. You suggested they were still there but being covered over by new dust, and then cited a figure for the erosion of rock - a totally irrelevant figure for this debate as tracks are not made into rock, they are made into the soil

The word 'erosion' is perhaps not geologically dictionary definition correct - perhaps 'remodelling' is a more appropriate word. Dust, soil getting moved around to render the physical imprint of tracks less obvious over time. Not just a dusting over the top, an actual softening and reduction in depth and detail of the tracks themselves. That erosion is perhaps not the right word to use, doesn't mean that deposition is the process occurring.

The in situ evidence we have on this particular subject is this.

MI imagery of year old and new tracks at the same point at Endurance crater showed that the old tracks were being 'eroded' away, not covered up. The old tracks had pushed berries into the fine soil - and the passage of a year had allowed the tracks to be rendered much smoother by the dust being blown away starting the process of returning the soil-berry balance back to what it was.
http://marsrovers.jpl.nasa.gov/gallery/all...unity_m319.html
http://marsrovers.jpl.nasa.gov/gallery/all...unity_p319.html

After an array cleaning event near Larrys Lookout, tracks were not 'covered up' - they were very nearly blown completely away by strong winds.
http://pancam.astro.cornell.edu/pancam_ins...pasorobles.html

HiRISE imagery of Purgatory Ripple shows a large bright streak from the site where brighter soil was dug up by Opportunity. The soil that got dragged up isn't getting covered it, it's getting blown around.

Yes - dust covers things up - it covers up the solar arrays, it covers up the sapphire windows of Pancam and the MI's - but it's not, by a long shot, the only reason that tracks are rendered less visible over time. We have an observed physical remodelling going on, not simply an obscuration by falling fines.

Doug

[climber]

Doug,
When you show us the before/after (storm) for parrachutes, does the full image also cover Home Plate? If yes, are the old tracks visible somewhere?
Thanks

[djellison]

If yes, are the old tracks visible somewhere?

Nope - from that first HiRISE image (which was when Spirit was at Low Ridge Haven) - the tracks are essentially gone from Mitcheltree Ridge and before.

Doug

[Cugel]

That was the point you were making. This wasn't a debate about the erosion of rocks, hills, and mountains. This was about the disappearance of tracks on the ground. You suggested they were still there but being covered over by new dust, and then cited a figure for the erosion of rock - a totally irrelevant figure for this debate as tracks are not made into rock, they are made into the soil

I respectfully disagree. If someone calls something erosion I think quoting an article on erosion rates in a response is not 'totally irrelevant'.
Anyway, the number I quoted is at least interesting because if the erosion rate on mars is as low as given than it is amazing how quickly those rover tracks degrade. Having read that article I knew this incredibly low number and that is what triggered me in posting that rather silly remark about those 3 months etc.

I hope I understand HDP Don correctly in that Mars is very good in 'transportation' of this dust because of the lack of humidy, which prevents it from cementing to the ground. So, my view of Mars is that it is covered in this global blanket of dust which it can move around very actively but that the underlying rock layers are eroding at an extremely low rate.

[dburt]

Anyway, the number I quoted is at least interesting because if the erosion rate on mars is as low as given than it is amazing how quickly those rover tracks degrade...
I hope I understand HDP Don correctly in that Mars is very good in 'transportation' of this dust because of the lack of humidy, which prevents it from cementing to the ground. So, my view of Mars is that it is covered in this global blanket of dust which it can move around very actively but that the underlying rock layers are eroding at an extremely low rate.

I think the problem arose because you SEEMED to be equating erosion of solid rock with continuing wind transport of loose dust. The tracks in dust are easily lost because it is continually "in transit" to somewhere else, at least in principle. (May the same soon happen to the dust on Spirit's solar panels!) So yes, you understood me correctly. Dust does seem to get trapped at the poles, BTW, where the humidity (or chemical activity of the stable phase of H2O - ice) is higher.

[Aussie]

I feel compelled to leap to Cugel's defence. His statement So, my view of Mars is that it is covered in this global blanket of dust which it can move around very actively but that the underlying rock layers are eroding at an extremely low rate. seems correct to me. We have seen winnowing and erosion of tracks where the lag deposit has been disrupted by the rovers. Movement of a couple of berries presumabley initially unbedded by the rover, but no effect whatsoever on the untouched lag deposit at Meridiani. We have also seen micro scale ripples moving in what is apparently the highest level of wind kinetic energy nomally experienced on the martian surface but no major movement, so the sandblasting analogy has no place in the martian environment which is in effect a industrial level vacuum. The bottom line is that we have seen transport and deposition of extremely small dust particles, but not erosion! But over a few million years - perhaps a different story.

Secondly if impact surge was the cause of all we see on Mars then I would expect to see similar remnants on Earth attributable to, for example, the Popigai, Sudbury etc events. These do not seem to exist. Doug, could you reserect the impact surge thread for them that wants to discuss that subject and thus leave the Victoria threads for those that want non impact related viewpoints.

[djellison]

Doug, could you reserect the impact surge thread for them that wants to discuss that subject and thus leave the Victoria threads for those that want non impact related viewpoints.

Sorry - that discussion ran its course ( and in doing so, Don wrote enough words for a medium sized novel ).

When that thread was closed, I said

"If people wish to discuss his Meridiani theory further, then please do so elsewhere or via email.

Posts in other threads on this subject will be deleted - as a subject it's been exhausted with this thread."

Line in the sand is here.

----------------------

The above promise will be stuck to hereafter. I have reopened that thread so that stuff can be moved over into it. Without meaning to sound all condescending and overly sarcastic in a British sense of humor way I do feel a "What did I say about surge? What did I say? Get to your room!" coming on.

-------

Surge posts by Don & responding posts moved to the Surge thread : http://www.unmannedspaceflight.com/index.p...0&start=300

If anyone spots any I've missed - give me posts numbers and I'll tidy up.

We've done that subject to death guys - I will leave that thread open if you MUST discuss it - but multi-thousand word missives are simply not acceptable anymore.

Doug

[Guest_PhilCo126_*]

Sometimes I think that the 'False color' panoramas look better than the 'Real color' versions

[Stu]

Sometimes I think that the 'False color' panoramas look better than the 'Real color' versions

Some of my most... energetic arguments with my publishers have been over the use of false colour images. They see a garish, LSD-inspired false colour image of Saturn or Uranus and go crazy for it, thinking it looks "dynamic" and "colourful", which I suppose it is but it's also pretty useless for illustrating a kids space book without a big disclaimer, and there's never enough room in the text for one of those, of course...

Recently I was working on a new book and the dummy spreads came back to me in an email, and looking at the "Mars: The Red Planet" spread I found a false colour image of one of Victoria Crater's outcrops, in which it looked bright blue. I told my editor it was wrong for the spread because it was a false colour image, and it was a bit silly using it when there were perfectly good real colour images available. He wrote back that they wanted to use it because it was "visually stimulating" and "looked amazing". I pointed out that they had called the spread "The Red Planet" and let him know that it would be his job, not mine, to answer all the irate and puzzled emails from space cadet kids who had been baffled by how a red planet had blue rocks...

Bye bye false colour image

[Guest_PhilCo126_*]

Point made Stu, but this is still one of my favorites: labeled Spirit pan http://marsrovers.jpl.nasa.gov/gallery/panoramas/spirit/