"Would CRISM distinguish between clays and hydrated minerals like jarosite? And why so much on the crater floor? Hydrated subsurface layers that deep, or brought down from near the surface by the impact?

(not a geologist)"

Younger hydrated material filling an old crater.

Phil

OK - clearly I couldn't have been more wrong; MI's very different from generic bedrock. D'oh

Edit: the Wray et al paper seems (from a quick skim) only to discuss outcrops / exposures inside Endeavour's rim.

Fine-grained uniform stuff. Orthogonal weathering cleavages from weathering. Couple imbedded lighter objects.
Mudstone?

The horticolor version is reversed 180 degrees. I'm too lazy to figure out which is upside down.
Click to view attachment

Zoom of white object embedded in rough center of MI mosaic:

Click to view attachment

(1/2 scale zoom of two combined 10x-images (= 5x original). Contrast-enhanced.

It could be bright due to the angle of the light. Definitely pitted.

Tesheiner and Centsworth_II, thanks for the enhancements of the latest MI work -- and my God, what an incredible sight it is! It brings to mind so many things I don't even now where to start, so I will just throw out a couple of breathless thoughts.

First -- and I am not sure if it is even permissible to allude to this......




ADMIN ..... so why post it? Please don't intentionally and knowingly add to the administrative workload.

Just to be clear, I posted the work of talented image worker Hortonheardawho.

You should have just said, "it's like being there..."

I think you actually said its better than being there, but I don't think you'd get a lot of agreement on that.

Yesterday, a full set of right-filter images of Marquette came down. I made a right-filter, false color composite to see if this rock mineralogically resembled typical Meridiani sediments. This is the same false color image from right filter ratios that we've seen used in the past to emphasize the hematite concretions in these rocks. These RGB composites use R=R1/R2, G=R1, and B=R5/R7. An example from early in the mission is available here.

I won't speculate as to the mineralogy of Marquette, but it has a very different color and appearance in this image compared to typical Meridiani sediments. Remember, this is made from raw imagery which can only be used qualitatively. You can compare its yellow color to the blue color of the bedrock beneath it. The purplish hues are artifacts of the shadows. This image also shows that most of the cobbles lying around here display the same colors as Marquette, and therefore are probably fragments of the same original body.
Click to view attachment

From today's batch of pancams: http://nasa.exploratorium.edu/mars/opportu...cam/2009-11-16/
Click to view attachment Click to view attachment Click to view attachment

Wilderness, Voight, and Hessel Bays.

The texture and fabric of Marquette in the MI's looks like a micro-vesicular extrusive igneous rock, with some vesicles filled with lighter-colored minerals. That may include a pre-impact origin as a lava flow (basalt), dome (intermediate/andesite), or pre-existing impact melt. Like me in Texas, it ain't from around here...

Fairly quick hand stitched, processed and colourized panorama of NavCams from Sol 2066 (Mon 16th Nov - today) - time flies when you are having fun - that kept me up later than I realized!

Click to view attachment

My first impression, too. Looks like a piece of basaltic "basement" ejecta. Easy to spot with the R721 images. From the looks, this rock has had an interesting history. There should be some more MI handlens images today.

--Bill

A couple more mosaics from a while ago as I continue to catchup:

Nautilus Crater


Falcon Crater

With all the activity and expectations (knock on wood!) on Spirit today, the information about her sister at the other side of the planet was left a little bit behind. Just checked the tracking web to know about the imaging plan and found that the RAT will be used tomorrow, sol 2068.

Did NASA-JPL give an estimate of the size of "Mackinac" meteorite ?

Ready to brush / grind this rock?
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That's a good pre-grind position. Time for some rock-chomping, not done any for a while

Interesting! We kind of debated the value of grinding and gave a No Go. Is JPL still reading us?
OK, they'll may be "only" brush; but I wonder whether they choose to "attack" Marquette because of very big interest or because they consider "interesting enough" to use the tools since it's supposed to work (I know, we had a fault last time) instead of saving it for Endeavour with no garenty to get to there. This is the same debate as whether or not trying to move Marquette considered a few days ago by Deimos with very interesting rationales.

I'd have gone for it because we need down time for the FR wheel - it's presenting itself very well for IDD work given the limitations of the IDD since its trouble - and it's fairly unique, perhaps deep ejecta from a nearby crater.

Does the decision to grind indicate a preliminary low estimate of the hardness of the rock? (So that the amount of wear would likely be small?)

I haven't heard anything to indicate that this is a grind rather than just a brush. We should find out soon though.

I have tried to find estimates of what percentage RAT bit wear would be expected when drilling into different rock types. The only quote that I found was from:

www.dtm.ciw.edu/users/lrn/preprints/schroeder07accepted.pdf

"No attempt was made to grind the rock because laboratory tests using an engineering model of the RAT on an iron meteorite sample suggested abrading Heat Shield Rock would have led to rapid and substantial bit wear."

I remember it being said that this experiment caused 25% RAT bit wear but can not find the quote.

Spirit was able to RAT 16 rocks before its RAT's bit was ground down to nothing. I assume that the surface layers of the rocks RATed by Spirit had the average hardness of a slightly weathered basalt. I also assume that Marquette is a rock with the hardness of a basalt. I therefore think that RATing Marquette will use up 1/16 of the capacity of a brand new RAT.

I remember reading that Opportunity had used 75% of its RAT's capacity when it left Victoria Crater, but again I can not find the quote. If my figure is correct then I think that RATing Marquette will use up 1/4 of Opportunity's remaining RAT capacity. I am assuming that the hole will be of average depth.

Today's imaging plan is basically dedicated to take pancam shots of the rocks around Marquette. Like always, they are being named and among them we have:

02069::p2587::23::13::13::0::0::2::28::pancam_echo_island_quarter_L234567Rall
02069::p2588::23::13::13::0::0::2::28::pancam_birch_island_quarter_L234567Rall
02069::p2589::23::13::13::0::0::2::28::pancam_rover_island_quarter_L234567Rall
02069::p2590::23::13::13::0::0::2::28::pancam_gravelly_island_quarter_L234567Ral
l

"Gravelly island"?!?!? That's it, I *demand* a "Craggy island"!!!!

Odd ripples in the bedrock in the rover island quarter
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Here's an extract of the latest status report:

'Marquette' Study Begins
...
The rock abrasion tool (RAT) on the arm will lightly brush the rock to reveal the surface beneath the layer of dust. After receiving the results of the RAT brush, the science team will decide whether to look even deeper into the rock by grinding a couple of millimeters (about a tenth of an inch) down into it and performing additional science observations.
...

BTW, a bunch of MIs of the brushed area are available here: http://qt.exploratorium.edu/mars/opportuni...ger/2009-11-20/

Here's a quick mosaic of the MIs.
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Metallic looking. Another meteor?

That brush is really useful, isn't it? Not what I was expecting to see at all.

All the basalt rocks Spirit brushed looked shiny like this - it's not a sign of a meteorite specifically.

Phil

Yeah. It may be a misplaced weathered piece of basalt, just like 'Bounce' rock

Phenocrysts? A healed fracture? Peridotite (or gabbro)?

I checked today "Mars Forum", mainly due to Horton's work. Horton has posted today a beautiful MI mosaic of brushed area on Marquette Island.
http://www.flickr.com/photos/hortonheardaw...655198/sizes/l/
Horton's works are excellent as usual.

Something about the look of the brushed rock says "Olivine" to me. No real factual basis...

Marquette Island might be a meteorite afer all.

http://marsrovers.jpl.nasa.gov/gallery/pre.../20091125a.html

I'll be damned.

Makes me wonder if we've seen any rocks @ Meridiani that aren't meteoritic aside from the clearly native 'paving stones'.

Tell ya... Meridiani = meteorite hunter's paradise

I reckon it's a bit of Phobos. (Just a fun guess)

I wonder if it could be a meteorite that actually originated on Mars (ejected, later reentered).

See post 589. No answer yet about what is a meteorite.

You asked for it, my own expert opinion.

Any rock that has orbited any object in the solar system, including the sun, is a meteoroid. If it falls to the surface of any body in the solar system, it is a meteorite.

A rock on Mars could have been at one point a meteoroid that originated from Mars, but as it would be near impossible to distinguish it from other ejecta that fell back to Mars, the question of whether it is a Mars meteorite on Mars is moot. Unless...

Some way might be found to show a Mars rock had spent a long period of time in interplanetary space, I don't know.

If it is a Mars rock that spent some time in space wouldn't we know that from its composition? Ejecta would have still gone through the eons of Mars' surface climate?

Only thing I can think of is to check for iridium & other rare-earth enrichment, but dunno if the APXS is still capable of that (and, actually, don't know what the normal Martian baseline values are for rare earths...)

If that's possible, might at least eliminate it as surface ejecta (whenever/wherever that would have happened). I can't think of any tests that Oppy could do to tell if it was a Martian rock that spent time in space before re-entering.

If it is not Martian, then could it be still a piece of the impactor that caused Fresh crater or is there no chance that single pieces can survive the impact? Shouldn't a single stony meteorite still show a bit of the hardened crust from the entry? At least, it should then have another look from the "weathering".

Bounce has the composition of a typical Mars meteorite. However on Mars Bounce is not a meteorite because it is still on the planet that it originated from.

It may be my impression but...didn't Oppy just put Marquette to the floor with a might uppercut?...
http://qt.exploratorium.edu/mars/opportuni...R5P1110L0M1.JPG

EDITED: Yes, just my impression...where did I put those glasses?

We can see many smaller fragments of similar looking rock scattered around, so presumably MI isn't the entire original impactor. If we're lucky and it hasn't eroded away maybe pieces of the original entry surface are still on some of the fragments around though.

As I understand, Bounce is not a meteorite because it presumably has never been in orbit. But suppose it had. Bounce is suspiciously similar to some Mars meteorites on Earth. It's possible that the same impact that sent Bounce to land in Meridiani also sent some fragments into solar orbit which eventually landed on Earth. Perhaps it's also possible that some fragments that were in solar orbit also fell back to Mars, not that Bounce is one of those.

The official scientific definition of "meteorite" could include the provision that a rock , even after millions of years of solar orbit, that falls on the planet of it's origin is not a meteorite. But I don't know that it does. The question is probably moot. But if it could be determined that a rock from mars spent millions of years in solar orbit before falling back to Mars, why would you not call it a meteorite? It certainly has a history which is much different from the typical Mars rock.

Or, a piece of deep ejecta: