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Posted by Robert Clark on September 6, 2006, 7:15 pm
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Just saw this on Unmannedspaceflight.com:
Mineralogy of the light-toned outcrop at Meridiani Planum as seen by
the Miniature Thermal Emission Spectrometer and implications for its
formation.
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, E12S03,
doi:10.1029/2005JE002672, 2006
"Abstract
Analysis of Miniature Thermal Emission Spectrometer (Mini-TES) data has
led to the recovery of a pure end-member spectral shape related to the
light-toned outcrop observed at Meridiani Planum. Data from the MER
M=F6ssbauer spectrometer, APXS, and previous Mini-TES measurements were
used to constrain a spectral library used to determine the mineralogy
of the outcrop from this spectral shape. Linear deconvolution of the
outcrop spectral shape suggests that it is composed primarily of
Al-rich opaline silica, Mg-, Ca-, and Fe-bearing sulfates, plagioclase
feldspar, nontronite, and hematite. Conversion of modeled mineralogy to
chemistry shows good agreement with the chemical composition of the
outcrops determined by APXS. Details of the analysis procedure and
implications for the formation of the outcrop are discussed along with
terrestrial analogs of the ancient environment at Meridiani."
http://www.gps.caltech.edu/~tglotch/2005JE002672.pdf
According to the authors the spectra of the Meridiani bedrock is best
matched by a composition that includes 10% nontronite clay.
Bob Clark
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Posted by jonathan on September 6, 2006, 10:37 pm
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Just saw this on Unmannedspaceflight.com:
Mineralogy of the light-toned outcrop at Meridiani Planum as seen by
the Miniature Thermal Emission Spectrometer and implications for its
formation.
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, E12S03,
doi:10.1029/2005JE002672, 2006
"Abstract
Analysis of Miniature Thermal Emission Spectrometer (Mini-TES) data has
led to the recovery of a pure end-member spectral shape related to the
light-toned outcrop observed at Meridiani Planum. Data from the MER
Mössbauer spectrometer, APXS, and previous Mini-TES measurements were
used to constrain a spectral library used to determine the mineralogy
of the outcrop from this spectral shape. Linear deconvolution of the
outcrop spectral shape suggests that it is composed primarily of
Al-rich opaline silica, Mg-, Ca-, and Fe-bearing sulfates, plagioclase
feldspar, nontronite, and hematite. Conversion of modeled mineralogy to
chemistry shows good agreement with the chemical composition of the
outcrops determined by APXS. Details of the analysis procedure and
implications for the formation of the outcrop are discussed along with
terrestrial analogs of the ancient environment at Meridiani."
http://www.gps.caltech.edu/~tglotch/2005JE002672.pdf
According to the authors the spectra of the Meridiani bedrock is best
matched by a composition that includes 10% nontronite clay.
Bob Clark
So that would mean a less acidic environment that is more friendly
to life I believe. All those layered rocks and outcrops were formed
by evaporation of shallow seas and weathered by water.
Doesn't this paint a picture of Mars that has substantial underground
water that flows to or near the surface periodically? Alternating wet
and dry periods. Perhaps as ice ages wax and wane?
The article also claims that water is about 5% by weight of the outcrops.
It's starting to look like water, not volcanism, is the more active
weathering process.
The idea that Mars has been dry for geologic time just doesn't
sound anything at all like the truth. Does anyone know how
long Mars ice ages last? I'd suspect they'd be rather
chaotic with the complicated orbit.
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Posted by marsfossils on September 7, 2006, 4:58 pm
Please log in for more thread options Interesting. Thanks. For those of us who didn't know what nontronite
clay is....
> According to the authors the spectra of the Meridiani bedrock is best
> matched by a composition that includes 10% nontronite clay.
We note from Wikipedia: http://en.wikipedia.org/wiki/Nontronite
>>Nontronite forms from the weathering of biotite and basalts, precipitation of
iron and silicon rich hydrothermal fluids and in deep sea hydrothermal vents
(Bischoff, 1972, Clays and Clay Minerals, 20:217-223; Eggleton 1975 American
Mineralogist, 60:1063-1068). Some evidence suggests that microorganisms may play
an important role in their formation (Kohler et al., 1994 Clays and Clay
Minerals, 42:680-701).<<
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Posted by jonathan on September 7, 2006, 8:21 pm
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> Interesting. Thanks. For those of us who didn't know what nontronite
> clay is....
Remember the very first question that arose after Opportunity landed?
Why does the soil act like it's clay?
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/001/1P128287557EFF0000P2303L2M1.HTML
If Mars has been dry and irradiated for hundreds of millions of years,
there's
no way the soil should be clay-like. It should be sand-like, or powdery.
Yet, there it was. An intermediate form and grain size.
From day one a mystery.
And from day one I strongly suspected Meridiani was a special place.
As the union of opposite extremes are always a sign of a system that
is dynamic and evolving. Neither sand or powder, but both.
The very first thing the rovers made me do was to go to
Wikipedia and read about clay.
And I was hooked on Mars.
I don't care what they say, this rover mission is the best
space mission of all time. Apollo was exciting, but this
mission asks more questions, inspires more thought than
any space mission to date.
And it's a robotic mission. Ya know, sending people would
allow them to do the interpretations, and we would simply listen.
But a robotic mission like this forces....us....to do
the observing.
I now believe robotic missions are far superior than manned
missions. Manned missions place a few there.
A robotic mission places each and every one of....us...there.
To figure it out for ourselves.
Jonathan
s
>
> > According to the authors the spectra of the Meridiani bedrock is best
> > matched by a composition that includes 10% nontronite clay.
>
> We note from Wikipedia: http://en.wikipedia.org/wiki/Nontronite
>
> >>Nontronite forms from the weathering of biotite and basalts,
precipitation of iron and silicon rich hydrothermal fluids and in deep sea
hydrothermal vents (Bischoff, 1972, Clays and Clay Minerals, 20:217-223;
Eggleton 1975 American Mineralogist, 60:1063-1068). Some evidence suggests
that microorganisms may play an important role in their formation (Kohler et
al., 1994 Clays and Clay Minerals, 42:680-701).<<
>
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Posted by Robert Clark on September 13, 2006, 7:15 pm
Please log in for more thread options jonathan wrote:
>
> > Interesting. Thanks. For those of us who didn't know what nontronite
> > clay is....
>
>
> Remember the very first question that arose after Opportunity landed?
> Why does the soil act like it's clay?
>
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/001/1P128287557EFF0000P2303L2M1.HTML
>
> If Mars has been dry and irradiated for hundreds of millions of years,
> there's
> no way the soil should be clay-like. It should be sand-like, or powdery.
> Yet, there it was. An intermediate form and grain size.
>
> From day one a mystery.
>
> ...
A good point. Two separate and independent observational means show
there is seasonally varying water content on the Martian surface: one
by thermal infrared spectra, the other by the Gamma Ray-Neutron
Spectrometer.
TES and Mini-TES spectra showed seasonal variations of carbonate dust
on the surface. It was suggested this was formed from water vapor.
However, on Earth in nature carbonate is formed from *liquid* water.
It is very likely it is formed from liquid water on Mars as well:
From: Robert Clark
Date: Sat, Feb 11 2006 10:32 pm
Groups: sci.astro, alt.sci.planetary, sci.physics, sci.geo.mineralogy
Subject: Could We Make A "Solar Still" On Mars?
http://groups.google.com/group/sci.astro/msg/95e5bae350f8c285?
This report shows clays can be formed in short times under martian
conditions:
MINIMUM TIMES TO FORM CLAY IN MARTIAN SURFACE AND NEAR-SURFACE
ENVIRONMENTS.
L. Browning1, G. J. Taylor2, and D. Pickett1
1Center for Nuclear Waste Regulatory Analyses, Southwest Research
Institute, 6220 Culebra Rd., San Antonio, TX 78228 2 Hawai'i
Institute of Geophysics and Planetology, University of Hawaii,
Honolulu, HI, 96822
Lunar and Planetary Science XXXIV (2003) 1708.pdf
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1708.pdf
I suggest searching the infrared spectra to see if the signature for
clays also varies seasonally as does the carbonate dust signature.
If it does then this will mean the clays are currently forming and
will imply they are also being formed from liquid water as is the
carbonate.
Bob Clark
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