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Mars Rover Spirit Unearths Surprise Evidence of Wetter Past
ngunn
post May 23 2007, 02:23 PM
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I'd love to know that too; I hope somebody can help us out.

My question about anhydrous or hydrated arose from the two related facts I do know - that anhydrous silica is a powerful dessicant but so is the Martian atmosphere. I just wondered which has the upper hand here.
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slinted
post May 23 2007, 10:13 PM
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This was quite a shocker for me, since I'd been looking at the pictures of Gertrude Weise and thinking it was another exposed sulfate deposit. If it looks like sulfates, and gets disturbed like sulfates it must be... 90% silica!?
This does lend credence to the theory that the localized deposits are based on the composition of the underlying bedrock. Also, this would put the action of liquid water later in the relative timeline than any of the geologic evidence. After the underlying bedrock was formed it was exposed to liquid water, which concentrated the soluble elements close to the surface where the water would evaporate.

Expanding (and duplicating) on the images from the press release, here are some of the exposed bright patches Spirit has seen recently:

Sol 1187


Sol 1194


Sol 1198, which shows two distinct units being exposed, the brighter/whiter on the left, and the blue/grey on the right
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tglotch
post May 24 2007, 12:40 AM
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QUOTE (CosmicRocker @ May 23 2007, 05:08 AM) *
As much as I am drooling over the thought of MSL on Mars, I sure would feel better if there were two of them. I think there is some merit in the multi-MER concept. They are dynamite little explorers that have proven themselves and their EDL concept, but I think you run into a problem budgeting the large crew needed to keep many of them operating and exploring efficiently.

Getting back on topic...

That's an interesting question. If this silica is truly amorphous or non-crystalline, there can't be any water of crystallization. Besides, I am not aware of any crystalline form of silica that holds water. But opal is an amorphous form of silica that does contain variable amounts of water.

I don't know how they know that this silica is non-crystalline. Which instrument tells them that, or how do they infer it? I would suspect that if this material was not anhydrous, that fact would be widely advertised as further proof of water once on Mars. I think the mini-TES can see water wherever it may be.



The Mini-TES is the instrument that determined that the silica is amorphous. The spectral character of amorphous or opaline silica looks quite different from quartz or one of the other crystalline polymorphs of SiO2.

As for water, the Mini-TES can qualitatively assess hydration state of soils by looking for a spectral feature near 6 microns. As far as I know (and I'm not positive), this white, silica-rich soil does not have a strong 6 micron feature, implying low or no water content in the silica.
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Stephen
post May 24 2007, 03:20 AM
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QUOTE (djellison @ May 23 2007, 08:03 AM) *
If MSL works - you've got many orders of magnitude more Mars that can be accessed, and then it does make some sense to think about reusing MSL or indeed just its decent stage to deliver payloads.

True. But wouldn't an MSL also be a lot more expensive than an MER? With NASA already paring science and unmanned missions back to the bone in pursuit of the VSE it may not have the money to choose the Rolls-Royce of rovers over the Ford econovan version. Especially if scientists wanted to send more than one at the same time.

(In that context I notice that MEPAG in this document:

http://mepag.jpl.nasa.gov/reports/3715_Mar...l_Strat_GPO.pdf

tentatively advocates (for the 2016 opportunity) either "two MER-derived rovers" it terms "mid rovers" but only a single MSL-derived Astrobiology Field Rover.)

I also seem to remember the US currently have a plutonium shortage. Until that is addressed there will doubtless be a limit on how many MSL-style rovers can be despatched unless they were solar powered; and wouldn't a solar-powered MSL suffer from some of the same restrictions the solar-powered MERs have to put up with?

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Stephen
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CosmicRocker
post May 24 2007, 04:16 AM
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QUOTE (tglotch @ May 23 2007, 07:40 PM) *
The Mini-TES is the instrument that determined that the silica is amorphous. ...
Thanks, Tim. In retrospect, I suppose I should have realized that. The mini-TES is quite a useful tool that often is neglected by enthusiasts. It has no nearly-real time equivalent to the raw jpeg images we get from the visual cameras, and its work is seldom illustrated in the news releases.

slinted: You're right. I think the initial, bright appearance fooled some of us into thinking it was the same old bright stuff. Now that we know better, check out the texture of that material. The large grain size is visible in the pancams, and that is quite different from the fine powder we've seen from the sulfates.


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...Tom
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David
post May 24 2007, 06:52 AM
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QUOTE (AlexBlackwell @ May 21 2007, 08:19 PM) *
Mars Rover Spirit Unearths Surprise Evidence of Wetter Past
NASA/JPL
May 21, 2007


Surely Spirit rather "Unmarses" this evidence? biggrin.gif

("Digs up" would do just fine too.)
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dilo
post Jun 3 2007, 07:29 AM
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New Sol1213 exposed bright patches (L257):
Attached Image


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I always think before posting! - Marco -
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Guest_Oersted_*
post Jun 6 2007, 02:48 PM
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Guests






Spirit wants to sniff that more badly than a coke addict! cool.gif
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