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| Titel |
Curiosity Rover’s CheMin Instrument Investigates Mineralogy of Gale Crater and Implications for Diagenesis |
| VerfasserIn |
Kim Fendrich, Elizabeth Rampe, David Vaniman, David Bish, David Blake, Allan Treiman, Doug Ming, Richard Morris, Tom Bristow, Patrick Cavanagh, Robert Downs, Shaunna Morrison, Steve Chipera, Cherie Achilles, Jack Farmer, Philippe Sarrazin, Joy Crisp, John Michael Morookian, Albert Yen, Ralf Gellert |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108001
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| Publikation (Nr.) |
 EGU/EGU2015-7730.pdf |
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| Zusammenfassung |
| The Mars Science Laboratory rover Curiosity employs a suite of instruments to investigate
past or present habitability of Mars, as observed at Gale crater and particularly in the lower
strata of the crater’s central mound, informally named Mount Sharp. The X-ray
diffractometer on board, CheMin, is used to assess the quantitative mineralogy of scooped
soil samples and drilled rock powders. Methods of modeling diffraction peak positions and
intensities to evaluate the abundances of minerals include Rietveld refinement and FULLPAT
(full-pattern fitting). Each of the samples analyzed by CheMin contains X-ray amorphous
material. The amorphous component chemistry is resolved by subtracting the chemistry of
the crystalline composition, as determined by X-ray diffraction data, from the bulk
sample chemistry, as determined by the Alpha Particle X-ray Spectrometer (APXS).
Diffraction results have been obtained on five samples thus far to include Rocknest,
John Klein, Cumberland, Windjana and Confidence Hills. Soil samples collected at
Rocknest, an aeolian bedform in Gale crater, were the first to be analyzed in situ by
CheMin. The Rocknest mineral assemblage is basaltic (plagioclase, Fe-forsterite,
augite, pigeonite) and contains amorphous material that is compositionally similar to
palagonitic volcanic soils found on Earth, with the addition of sulfur and chlorine. The
four drill analyses are characteristic of deposition in a variety of fluvio-lacustrine
environments and exhibit evidence of low-temperature diagenesis. Both John Klein and
Cumberland are part of the Sheepbed mudstone at Yellowknife Bay, where the first drilled
samples were acquired as well as the first evidence of a habitable environment on
Mars. Drilled three meters apart from each other, the two samples reveal basaltic
minerals similar to those at Rocknest, as well as phyllosilicates, Fe-oxides/hydroxides,
Ca-sulfates, Fe-sulfides, and amorphous materials. The nature and hydration of interlayer
cations within the phyllosilicates differs between the two samples, which implies
localized diagenesis. The Windjana sandstone at the Kimberley location differs
from the Sheepbed mudstone in that it contains more pyroxene and magnetite and
abundant K-feldspar, as well as phyllosilicates and amorphous material. These
phases may represent potassium-rich basaltic provenance or aqueous alteration by
potassium-bearing fluids. While the Confidence Hills sample is still in the preliminary stages
of evaluation, major crystalline phases observed in this fine-grained sedimentary rock
include plagioclase, pyroxene, K-feldspar and phyllosilicates; hematite, rare in all
previous samples, is notably abundant and jarosite is present. The findings suggest
localized mobilization of iron-bearing fluids and acidic conditions. The more oxidized
assemblage of Confidence Hills marks the transition into the lower strata of Mount Sharp. |
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