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Bound water on Mars
alan
post Oct 19 2007, 06:46 PM
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Physicists at the University of Guelph have detected the first "on-the-spot" evidence of significant amounts of water still existing on Mars.

Rather than existing in pools, the water is trapped in sub-surface soil on the red planet, most likely the remnants of oceans or pools that evaporated, according to lead researcher Iain Campbell.

"Our work is the first in situ evidence for total bound water in the Martian subsurface,” said Campbell,

An X-ray spectrometer called an APXS on the rover's arm captured the data about the trapped water. "Other instruments suggest the possibility — the APXs lets us determine the actual amount," said Campbell,

The water appears to be contained in mineral compounds in sulphur-rich soil just beneath the planet's surface, Campbell said. The distinctive bright white material was churned up by the rover's wheels as it moved across the soft red surface in the Columbia Hills region of the planet

In a paper that is in the final stage of review by the Journal of Geophysical Research: Planets, the team says the bright, sulphur-rich material contains up to 16 per cent water.


http://www.uoguelph.ca/news/2007/10/u_of_g_scientis_1.html
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mike
post Oct 20 2007, 01:20 AM
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Ah, to have been there at the moment it churned up what later became white matter.
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David
post Oct 20 2007, 03:47 AM
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QUOTE (mike @ Oct 20 2007, 01:20 AM) *
Ah, to have been there at the moment it churned up what later became white matter.


I don't recall any basis for the opinion that it wasn't white when "churned up".
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TheChemist
post Oct 20 2007, 07:50 AM
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Your recollection is correct, this is bound water we are talking about, it is part of the crystal structure of the salt it is contained in. Nothin churned up.
To me it is strange to come forward with the story when the paper is still "in the final stages of review". How do they know it will not be rejected ?
In any case a very interesting work, but let's wait for the article.
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djellison
post Oct 20 2007, 07:50 AM
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QUOTE (mike @ Oct 20 2007, 02:20 AM) *
Ah, to have been there at the moment it churned up what later became white matter.


Given that we're talking chemically bound water within minerals - I see no reason why it would wouldn't have looked the same when it was churned up as it does now.

Doug
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alan
post Oct 20 2007, 11:29 AM
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Changes thread title to be more precise.The first article I read about this didn't specify that the water was bound within the minerals.
http://www.theglobeandmail.com/servlet/sto...ry/Science/home
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slinted
post Oct 21 2007, 12:25 AM
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Although I'm not sure this is what Mike was referring to, some of the materials exposed at the Tyrone site did undergo a gradual color change from yellow to white after being exposed to the atmosphere.

from Salty Soils at Gusev Crater as Revealed by Mars Exploration Rover Spirit:

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...the “yellowish” soils appear to become more spectrally similar to the “whiteish” soils since the time of their exposure to Martian surface conditions. This observation supports our model of the layered structure of salty soils at Tyrone. Indeed, we hypothesize that the “yellowish” soils were originally not in equilibrium with surface conditions because they were buried deeper. Over time, the equilibrium has been developing thus the “yellowish” soils are becoming similar to "whiteish” soils, which were more or less in equilibrium with surface conditions because of their originally much shallower burial depth.
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dburt
post Oct 24 2007, 12:47 AM
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QUOTE (slinted @ Oct 20 2007, 05:25 PM) *
Although I'm not sure this is what Mike was referring to, some of the materials exposed at the Tyrone site did undergo a gradual color change from yellow to white after being exposed to the atmosphere.
from Salty Soils at Gusev Crater as Revealed by Mars Exploration Rover Spirit:

Like some others, I'm a little confused about this discovery. That LPSC abstract appears to cover pretty much the same ground as the Guelph news release, with different authors. From personal observation in Arizona, efflorescent yellowish hydrated minerals on mine dumps commonly turn into chalky powder as they dehydrate in summer. A still more familiar example is gypsum crystals in deserts like Death Valley, which can develop a chalky coating of bassanite (better known as "Plaster of Paris") as they partly dehydrate. That the martian surface was rich in sulfates, that presumably were strongly hydrated, and that these sulfates could dehydrate or rehydrate with varying conditions, is a result that at least goes back to Viking discoveries in the 1970's (e.g., numerous papers by Ben Clark), as does the idea that hydrated salts could be "mined" for water by early Mars colonists. The Gamma Ray Spectrometer instrument on Mars Odyssey indicated appreciable water near the Martian equator, where ice would need to be deeply buried, and as I recall this was ascribed most likely to bound water in salts. So the idea, at least, is hardly new, and the result is hardly surprising. Perhaps I read too much. smile.gif

-- HDP Don
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marsbug
post Oct 24 2007, 02:13 PM
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The impression I got from the article was that the 16% figure was a first and worth making a bit of a fuss about. If some of the water is present as fluid inclusions that would be exciting, but I dont know if theres any way that could have been determined.


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dburt
post Oct 24 2007, 06:53 PM
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QUOTE (marsbug @ Oct 24 2007, 07:13 AM) *
The impression I got from the article was that the 16% figure was a first and worth making a bit of a fuss about. If some of the water is present as fluid inclusions that would be exciting, but I dont know if theres any way that could have been determined.

"Up to 16%" in the news release doesn't sound like a measurement (and I'm not sure how such a measurement could be made by instruments available on the MER), but more like a calculation from formulae for various possible hydrated sulfates. Better to wait for publication of the peer-reviewed article in JGR for further comment, though. A significant content of liquid water as fluid inclusions is unlikely and, as you suggest, likewise could not be determined.

-- HDP Don
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slinted
post Oct 24 2007, 11:01 PM
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I'm anxious to see the actual paper as well, since some of the previous work trying to identify the exact sulfates has been contradictory (or at least muddled). Coming up with an fit that is consistent with the measurements of Pancam, miniTES, Mossbauer and APXS seems to be no easy task. ( see Identifying the Phosphate and Ferric Sulfate Minerals in the Paso Robles Soils (Gusev Crater, Mars) Using an Integrated Spectral Approach

HDP Don: Although I completely agree that this finding isn't Mars-shattering in its conclusion, I do find it interesting that we now have ground truth for some of the previously assumed forms of stored (in this case bound) water on Mars. We, through the rovers, may have actually touched the last gasp of surface water. Finding samples this pure helps to make sense of the GRS findings for equatorial water.
Also, although most of the sulfates could have gone through many cycles of dehydration and rehydration, I did find one paper from the 2005 LPSC that states that some of the ferric sulfates in particular may not be able to rehydrate (The Hydration and Dehydration of Hydrous Ferric Iron Sulfates). This may help put constraints on the atmospheric conditions when/if last these deposits were exposed to the surface.

Then again, I may just find this stuff interesting because it makes for such pretty pictures
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