Hello MER mission scientists. I was surprised to see in this interview that
the mini-TES instruments might only have days left of active life on the MER
rovers:

Martian dirt choking out ASU rover experiments
Dust comes as no surprise to ASU scientist Phil Christensen.
William Hermann
The Arizona Republic
Jul. 15, 2004 12:00 AM
http://www.azcentral.com/arizonarepublic/news/articles/0715asurovers15.html

If this is so I want to re-emphasize up close examination of rocks and soil
in Gusev that appear similar in composition to the mystery material seen in
Humphrey and Mazatzal rocks and on one side of Bonneville crater while the
mini-TES is still active.
I raised the possibility that this material might be the same as the mystery
material seen from orbit by TES in the northern hemisphere of Mars. The
discovery of this material by TES was listed at the top of the top 25
discoveries of the TES instrument:

Top 25 TES Science Results From Mars Global Surveyor
Tempe - Oct 4, 2001
http://www.spacedaily.com/news/mars-surveyor-01d.html

The material is called "andesite" here, but it could be liquid water altered
basalt, hence the mystery. Resolution of this question could be fundamentally important for the understanding of present and past geology and geochemistry of Mars.
Support of the idea that the mystery materials seen by TES and mini-TES are the same might be obtained by data returned by Pathfinder. Pathfinder also observed rocks that were termed "andesitic". However, since many of these rocks had characteristics of conglomerates, I would suggest that the data for these rocks might also be matched by liquid water altered basalt. This might determined by comparing the imaging spectra from the IMP camaras on Pathfinder with the spectra from the Pancam cameras on the MER rovers.

Bob Clark

_____________________

Robert Clark
Dept. of Mathematics
Widener University
One University Place
Chester, PA 19013 USA
_____________________

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From: Robert Clark (rgregoryclark@yahoo.com)
Subject: About the Bruce Moomaw article on Gusev, Mars.
Newsgroups: sci.astro, alt.sci.planetary, sci.geo.geology, sci.geo.mineralogy
Date: 2004-06-12 01:04:32 PST

Another nice article by Bruce Moomaw on the MER rover missions:

First Stop Gusev
by Bruce Moomaw
Sacramento (SPX) Jun 07, 2004
http://www.spacedaily.com/news/mars-mers-04zzzzw.html

However in it, he presents the view that the near surface of Gusev,
representing geologically recent material, may never have been
subjected to extensive water exposure:

"Not only is Gusev's main plain covered by windblown dry basalt-lava
sand - whose high content of the mineral olivine proves that it can
never have been exposed to liquid water for other than extremely brief
periods - but all the rocks Spirit has analyzed seem to be made of the
same never-wet basalt.
"Some of these basalt rocks have a thin water-weathered crust,
suggesting that they have been repeatedly exposed to thin films of
liquid water over the eons during Mars' endless hundred-thousand-year
"obliquity cycles" of increasing and decreasing axial tilt, which have
dramatic effects on the planet's seasonal weather even today.
"But we are still talking about only very small amounts of liquid
water, not the kind of extensive surface or near-surface liquid water
which scientists hope to find evidence that Mars had during its
earliest days, and which the two rovers were in fact designed to look
for (and which Spirit's twin "Opportunity" has in fact found on the
opposite side of the planet)."

However, I believe there is evidence to support the view there has
been recent, extensive near surface water there.

The reasons I discuss here:

From: Robert Clark (rgregoryclark@yahoo.com)
Subject: Mystery material in the Bonneville crater on Mars.
Newsgroups: sci.astro, alt.sci.planetary, sci.geo.geology,
sci.geo.mineralogy
Date: 2004-03-20 05:50:12 PST
http://groups.google.com/groups?th=4005c8b6bfcc019a

In short the material seen on one of the sides of the Bonneville
crater was similar to a mystery material seen on Humphrey and Mazatzal
rocks. This mystery material is interpreted to be either a high-silica
glass or a basalt weathering product, perhaps even clay.
This would be analogous to mystery material seen widespread from orbit
by MGS in the northern hemisphere of Mars that has been interpreted as
either andesitic rock or liquid water altered basalt. Either of these
interpretations suggest extensive liquid water in the northern
hemisphere of Mars. If the mystery material seen in Bonneville really
is representative of this mystery material seen from orbit that would
suggest extensive liquid water near surface and probably recent in
Gusev.
This is supported by the announcement of large amounts of sulfate,
upwards of 15%, in a trench dug by Spirit:

More Signs of Water Found on Mars.
By AAP 06/08/04 9:55 PM PT "We have found more evidence of salts, more
evidence for the action of water -- much more compelling evidence than
we have found anywhere else at Gusev,' Squyres told a televised press
conference at NASA's Jet Propulsion Laboratory."
http://www.macnewsworld.com/story/34331.html

This sulfate is within centimeters of the surface and is therefore
probably due to recent liquid water, near surface. Steve Squyres
suggests this may be due to small amounts of water percolating from
subsurface, but the large amounts of sulfate, 15%, argues for a large
amount of liquid water.

Note also the presence of olivine does not rule out the possibility of
liquid water near surface as has been proven by Opportunity at the
Meridiani landing site.

A question is why is the mystery material so limited in extent in
Gusev? An image showing this material on the side of Bonneville is
below. It may be the material is usually underground but was thrown up
by impact with the Humphrey and Mazatzal rocks and uncovered in the
Bonneville crater.
Note also that the andesite or altered basalt seen from orbit, called
Surface Type 2 by NASA scientists, is largely confined to the northern
hemisphere. If this is the same as the mystery material in Gusev, than
its limited extent may simply because Gusev in the southern hemisphere
is outside the largest areal extent of this material. There has also
been seen from orbit areas on Mars that have a combination of both
this Surface Type 2 and Surface Type 1, which is interpreted as common
basalt.
It would be interesting to find out if Gusev is one of these
transition regions.

Bob Clark

Spirit, Sol 84, uncalibrated color image by Daniel Crotty.