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Posted by: Shaka Oct 26 2007, 09:29 PM

What's with the recent Pancams of HP surface rocks scraped by the stuck wheel?

Reflections in some areas are so bright that the image flares dramatically. I've never seen this before from Mars rocks except in tiny spots on Comanche rock. Only man-made metal surfaces on the rovers and heat shields have dazzled like this.
The flares occur in both the left and right cameras and also in some Navcam shots. What are these rocks made of that they would reflect so brightly? Can there be accidental overexposures under unusual light conditions?
Can some "Image Mage" explain this as an artifact?

Posted by: tty Oct 26 2007, 09:40 PM

My immediate reaction was mica, but there are several minerals which can reflect like this. Pyrite for example which is more likely than mica from a chemical point of view.

Posted by: Bill Harris Oct 27 2007, 02:35 AM

I noticed it too, and I've been snagging Pancam images with many more examples of these specular reflections. Tis indeed unusual, and now the observation is in the hands of the Rover drivers. We need to see other perspectives of this phenomenon. They really stand out viewing as stereo pairs.

My first thought is that this is a hydrothermal area and these are sulfide deposits. Not to be overly dramatic, but this may well be the El Dorado of the mission.

--Bill

Posted by: Shaka Oct 27 2007, 03:01 AM

Hee Hee! Thar's GOLD* in them thar hills, podnuh!


*(fools')

Posted by: ElkGroveDan Oct 27 2007, 03:16 AM

A large faceted crystal will catch light that way, especially if you are using a flash in a cavern (I have examples from years gone by, but darn if I haven't gotten the slide scanner yet.). If this was on Earth I'd suspect quartz or halite (I won't even mention CaCO3). But I haven't been following the complex chemistry on this side of the planet.

Posted by: mhoward Oct 27 2007, 03:52 AM

FWIW, here's the context and a view of the same area from a different perspective. In the second image, I have blue arrows indicating where I think the "shiny" rocks are.

http://www.flickr.com/photo_zoom.gne?id=1768900770&size=l http://www.flickr.com/photo_zoom.gne?id=1768049829&size=l

Posted by: Shaka Oct 27 2007, 08:13 PM

It's all good, guys, but can someone put together a "true color" version at this stage? It'd be nice to know whether the glitter is white or yellow or whatever.
It was mentioned before that one of the PIs found volcanic glass in HP rocks. Could higher concentrations of that glass produce a shiny reflection? Seems logical.

Newest Pancams focus on one of the rocks:http://qt.exploratorium.edu/mars/spirit/pancam/2007-10-27/2P246747045ESFAVQWP2536L7M1.JPG

Can one of our codebusters check out the name of the rock? Hopefully this is our next destination.

Posted by: djellison Oct 27 2007, 09:39 PM

Without the calibrated RAD imagery, no.

Your best bet in the meantime is to keep an eye on this page - http://pancam.astro.cornell.edu/pancam_instrument/true_color.html
Doug

Posted by: Shaka Oct 27 2007, 10:24 PM

Thanks, Doug; it's bookmarked. Wow, I was amazed at the lack of contrast in those images - like everyday was in the worst of a duststorm, or a salmon fog.
Is everyone satisfied that they are the closest to what we would see if we were standing there? I mean in a spacesuit with a clear visor.
Anyhow, I hope some of our guys can scoop them with the approximate Exploratorium product. Damn, I'm panting for some MIs of that rock!

Posted by: dvandorn Oct 28 2007, 04:31 AM

See, I've been saying that the features along the boundaries of HP looked to me like the fine laminations you get at the edges of hydrothermal vents since last Martian fall. It's be really nice to find some mineralogical support for it!

BTW, last I heard (again a while back), there was still a pretty committed contingent on the MER science teams who favored a hydrothermal vent theory. I know we have a few people from those teams who post here on occasion -- can any of you comment on the thinking of the science teams as of late?

-the other Doug

Posted by: djellison Oct 28 2007, 08:44 AM

You can argue that one all you like (and you probably will, but not in this thread). No two people see the same scene exactly the same anyway. It's the MER's team best approximation. If you want a different persons take on it - try Dan's calibrated set that you can get via MMB - he has a different tack on it. The perception of colour is, at the end of the day, a rough, artistic science. There's a lot of science and many algorithms behind it - but it's essentially a judgement call at the end of the day. Different eyes, different monitors, different lighting conditions - none of which are calibrated. I have two screens at work - on one of them, Mars always looks crap - without fail. It just can't do justice to those colour ranges. My personal preference ( which is what this has to end up being ) is about half way between Dan's and the PC team.

Doug

Posted by: Bill Harris Oct 28 2007, 11:58 AM

And I've heard speculation that it is a volcanic glass, the idea quoted obsidian. It is likely not obsidian, since that "mineral" is derived from a felsic (rhyolitic/granitic) magma and everything we've seen here is basaltic. I'm not terribly hot on ig/met pet, so I'm not sure what is a basaltic volcanic glass. My initial and gut-ish intuition is a sulfide, since we have iron and sulfur and heat in abundance here. But this bright luster is significant . Not only do we have the major flare-producing rocks, there are aslo many small areas of "sparkle" visible.

One idea I've had is that we have an aluminum wheel that is locked up and being dragged. Could it be that the aluminum is rubbing off onto the hard rocks? That sounds unlikely, but I thought I'd toss it out.

Not subscribing much to conspiracy theories, but in the two L257 trios that have come down, each pair has a "data loss" area on a channel. Not unusual, it happens. But usually, the black data loss area has a fuzzy "jpeg border", and these two occurances have pixel-sharp data loss area borders, which is very unusual.

So much for the X-Files, we now return to the arena of rational discussion.

--Bill

Posted by: slinted Oct 28 2007, 12:13 PM

Thanks for your kind words Doug. I take as high praise being as far from your aesthetic sweet spot as the pancam team.

Unfortunately, there will be no true color to be had from the brightest parts of these images. Sometimes, the bled out spots in the raws are just an artifact of the stretching, and the real detail is there in the originals (Tyrone comes to mind...compare http://marsrovers.jpl.nasa.gov/gallery/all/2/p/788/2P196320388EFFAQAEP2396L7M1.JPG to one made http://www.lyle.org/~markoff/collections/2P196320388RADAQAEP2396L7C1.JPG). But when you see blooming around the object, like we're seeing in the latest pancams of these bright rocks, you can be pretty sure the calibrated files will be bled out too. All we'll get from these images are constraints on the brightness (no less than "x").

Posted by: Del Palmer Oct 28 2007, 03:47 PM

The former is caused by transmission loss, whereas the latter is due to sub-frame masking (deliberate removal of certain image areas before transmission). In this instance it's a way of managing the blooming issues.

Posted by: Bill Harris Oct 29 2007, 02:19 PM

There is a series of partial-frame L456 Pancams online. Most are of the solar cell deck but there are a few of the locked-up wheel and specular-reflection rocks-- evidently they are assessing the health of the Rover before heading off of Homeplate. One of the L456 color trios shows what certainly looks like aluminum from the locked-up wheel being scraped onto the rocks.

This does not bode well. As long as the wheel is intact and being dragged, the Rover should be driveable. But once the wheel wears through to an "open shell", the drag will markedly increase and she'll lose a great deal of mobility. Goddard/vonBraun may not be reachable, and they may be faced with the decision of where to park Spirit to transition from rover to sessile station...


http://nasa.exploratorium.edu/mars/spirit/pancam/2007-10-28/2P246746085EDNAVQWP2291L4M1.JPG

--Bill

Posted by: Phil Stooke Oct 29 2007, 02:24 PM

Bill, I wouldn't worry too much. If aluminum is being scraped off the wheel, it's got to be worse here on the solid rock than it will be in the loose soil, and how much bedrock like this are we going to see again? We probably have a long way to go before things get bad for that reason. Alternatively, let's dance a jig here and wear the whole wheel off!

Phil

Posted by: Tesheiner Oct 29 2007, 03:07 PM

I would say that *both* cases are caused by transmission loss. The pictures referred by Bill (in these two frames: http://nasa.exploratorium.edu/mars/spirit/pancam/2007-10-27/2P246747011ESFAVQWP2536L5M1.JPG, http://nasa.exploratorium.edu/mars/spirit/pancam/2007-10-27/2P246747152ESFAVQWP2537L7M1.JPG, I presume) have a sharp border because they are LOCO (no, no, not crazy, just LOssless COmpression ). The fuzzy border is seen only on those pictures with heavy compression applied, which is the normal situation but not on this case.

Posted by: alan Oct 29 2007, 04:54 PM

Data loss, twice? On both images?
http://qt.exploratorium.edu/mars/spirit/pancam/2007-10-27/2P246747152ESFAVQWP2537L7M1.JPG
http://qt.exploratorium.edu/mars/spirit/pancam/2007-10-29/2P246747152ESFAVQWP2537L7M1.JPG

http://qt.exploratorium.edu/mars/spirit/pancam/2007-10-27/2P246747011ESFAVQWP2536L5M1.JPG
http://qt.exploratorium.edu/mars/spirit/pancam/2007-10-29/2P246747011ESFAVQWP2536L5M1.JPG

Posted by: Bill Harris Oct 29 2007, 07:15 PM

Agreed, Phil, we can run her til the wheel falls off. I was cautiously speculating on something that I wondered about last year when our "three legged dog" resumed her trek. I suppose that it might even drag better on loose material if the "treads" were worn off of the bottom of the wheel.

I didn't mean to seriously mention the "C" word. I'm sure that there is nothing sinister about the odd data loss. Although I'm equally sure that they are having a field day with it at the Gelbe Platz down the street...

--Bill

Posted by: mhoward Oct 31 2007, 03:50 AM

Apparantly. At least, they've been filled in now.

http://www.flickr.com/photo_zoom.gne?id=1806457287&size=l

Posted by: fredk Nov 1 2007, 02:48 AM

A very nice reflective trail across the lower part http://marsrovers.jpl.nasa.gov/gallery/all/2/p/1353/2P246479016EFFAVPBP2408L7M1.JPG I particularly like the barely visible trail of glints from the rolling wheels across the very bottom of the frame.

Speaking of trails, I also really like http://marsrovers.jpl.nasa.gov/gallery/all/2/n/1356/2N246741672EFFAVQWP1605R0M1.JPG of the U-turn Spirit made around sol 1350. She came remarkably close to the steep dropoff at the edge of home plate!

Posted by: ElkGroveDan Nov 1 2007, 04:02 AM

That is cool. Perhaps they will title the image "http://en.wikipedia.org/wiki/Thelma_&_Louise Reconsider"

I'm really surprised by this trail of aluminum. The hardness and abrasive character of those rocks must be substantial. Of course if you've ever hiked across basalt you'll know the damage it can do. I once took an ill-advised off-trail hike through http://www.nps.gov/archive/crmo/home.htm and after only an hour and a half the sole of one boot was flapping up and down hanging on by just a few threads. I don't expect a dragging aluminum wheel would last very long in those environs.

Posted by: fredk Nov 1 2007, 05:08 AM

I'm not convinced this is scraped off aluminum. It could just be smoothed areas giving specular reflections of sky, or just uncovered areas much lighter in albedo than the surface. However, home plate is already quite bright, so this latter possibility sounds not too likely.

Posted by: AndyG Nov 1 2007, 11:09 AM

The rover masses 185kg. Divide by six wheels. Divide by three, for Mars gravity.

Picture dragging a ten kilo, 25cm diameter, aluminium wheel over rocks...I think the cleats would wear quite quickly, but I can't imagine much damage being done to the main "tyre" over short distances.

Andy

Posted by: monitorlizard Nov 1 2007, 12:03 PM

If this were scrapings of pure aluminum, or a pure aluminum alloy, putting the APXS on it would reveal it in an unambiguous fashion. I'm sure the rover team would be interested in finding out if this is happening to one their wheels. They probably already know the answer, they just don't want to tell us.

Posted by: Bill Harris Nov 1 2007, 12:12 PM

Even though I brought up the supposition that the satyrated areas might be wheel scrapings, I think this unlikely. I'm sure that there is some wear on the wheel being dragged over the rocks, but not ehough to leave a "streak".

We'll find out one of these days. Another strange happening in this corner of the universe...

--Bill

Posted by: tasp Nov 1 2007, 02:11 PM

IIRC my metallurgy training (going on 30 years, not a sure bet at this point [laugh] ) it would take pretty sharp tooling of a specific shape and 'angle of attack' to generate chips. Can't help but think dragging an aluminum wheel on hard rocks is going to yield small particles pretty much exclusively.

Posted by: Bill Harris Nov 3 2007, 01:47 PM

New L257 and R721 Pancams of a couple of these saturated areas are down within the past couple of days. Without a quick "handlens" view to confirm, I'm thinkingt that these areas look like a drusy coating on fracture surfaces of the rocks, which makes sense consdiering the hydrothermal/epithermal nature of this area.


--Bill

Posted by: Shaka Nov 6 2007, 08:27 PM

Extending the topic of interesting rocks on the surface of Home Plate, which I would hope are worthy of IDD examination as we make our way toward the 'north winter haven', to whit:

It appears to me that we have here a rock that has been split along a fracture plane by impact with the stuck wheel. This would be a fine opportunity to analyze the interior of the rock without needing a RAT. Just a quick brush and Bob's-your-Uncle! Since we have made the decision to winter on the sunny north slope of HP, we are within a few sols of easy traveling to get there. This leaves us months to explore the fascinating rocks all around us!

On that note have any of you code-friendly types managed to work out the identity of the rocks being referred to in the recent manager updates? E.G. Conundrum Peak, Pikes Peak, Mt. Sneffles, Mt. Eolus, Humboldt Peak, Gray's Peak, Elk, San Juan? JPL hasn't yet released labeled images.

P.S. How many would agree with me that the stuck wheel may just be the best thing that ever happened to Spirit?