[meteorite-list] Mars Express Reveals Link Between Ferric Oxides and Sulfates in Equatorial Region of Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 22 Dec 2008 13:38:58 -0800 (PST)
Message-ID: <200812222138.NAA16171_at_zagami.jpl.nasa.gov>

http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=43946

Mars Express reveals a link between ferric oxides and sulfates in
equatorial regions of Mars

18 Dec 2008

Observations made with the OMEGA imaging spectrometer onboard Mars
Express reveal very strong signatures of sulfates and ferric oxides in
Aram Chaos. Detailed morphological analyses indicate that the
concentration of ferric oxides in this region results from the
alteration of a sulfate rich sedimentary formation resting on the floor
of the crater.

These results are reported by M. Masse and colleagues in the 9 December
2008 issue of the Journal of Geophysical Research.

Aram Chaos is a 280 km crater located northeast of Valles Marineris.
This depression is connected to the Ares Vallis outflow channel by a 15
km wide and 2.5 km deep gorge cutting though the eastern wall of the crater.

In order to decipher the geological history of this area, Masse and
colleagues compared the mineralogical data provided by OMEGA with high
spatial resolution imagery from a number of Mars orbiters.

OMEGA observations are acquired with three detectors: Visible Near
Infrared (VNIR, 0.38 to 1.05 ??m), Short-Wavelength Infrared (SWIR,
0.93-2.73 ??m) and Long-Wavelength Infrared (LWIR, 2.55 to 5.2 ??m).
Images are obtained at a spatial resolution ranging from 300 m to 4 km
per pixel. For the study reported here the team restricted their
analysis to the spectral domain between 0.4 and 2.6 ??m.

In a systematic survey of ferric oxide signatures on Mars, Aram Chaos
exhibited the strongest signature. An in-depth analysis of the spectra
for this region revealed regions with mineralogical compositions
consistent with ferric oxides and with a mix of ferric oxides and
sulfates. Correlation of the spectral signatures with high resolution
images allowed Masse and colleagues to infer a formation scenario for
the Aram Chaos crater in which the depression seems to have been filled
by two sequences of sediments.

The older sediment corresponds to chaotic terrains whose mineralogical
composition cannot be ascertained since the region is covered by dust.

The younger one corresponds to a dome-shaped, 900 m thick, layered
sedimentary formation emplaced later on the chaotic terrains. The bulk
of this formation is composed of one single bright material containing
both sulfates and ferric oxides. After its emplacement, this dome-shaped
formation has been grooved by large eolian corridors. In these
corridors, eolian removal of the bright material has left local
accumulations, in the form of dark sand sheets and dunes of residual
grains enriched in ferric oxides. The processes involved in this
deposition are most probably very similar to the ones observed by the
Opportunity rover in Meridiani Planum suggesting a common geological
development process for both regions, and a possible role of water in
the past.


Reference publication:
Masse, M., et al., 2008, "Mineralogical composition, structure,
morphology and geological history of Aram Chaos crater fill on Mars
derived from OMEGA Mars Express data", Journal of Geophysical Research,
113, E12006, doi:10.1029/2008JE003131
Received on Mon 22 Dec 2008 04:38:58 PM PST