[meteorite-list] Mars Express Zeros In On Erosion Features

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 23 Mar 2009 16:25:08 -0700 (PDT)
Message-ID: <200903232325.QAA21709_at_zagami.jpl.nasa.gov>

http://www.esa.int/esaCP/SEM8MQJTYRF_index_0.html

Mars Express zeros in on erosion features
European Space Agency
19 March 2009

Mars Express has uncovered geological evidence suggesting that some
depositional process, revealed by erosion, has been at work on large scales
in the equatorial regions of the planet. If so, this would provide another
jigsaw piece to be fitted into the emerging picture of Mars' past climate.
 
The evidence comes from the mineralogical composition of the Aram Chaos
region, a crater 280 km in diameter lying almost directly on the martian
equator. Data from Mars Express' OMEGA instrument, the Visible and Infrared
Mineralogical Mapping Spectrometer, has revealed that this region shows a
significant amount of sulphates and ferric oxides. On Earth, ferric oxide is
more commonly known as rust.

Observations from Mars Express show that the bright red dust covering much
of the planet is enriched in ferric oxides. Yet in the dark deposits of Aram
Chaos, there is a four-fold increase in the spectral signature of ferric
oxides, revealing a specific concentration mechanism. Ferric oxides are
generally found with sulphates but, in this case, the lighter sulphates have
been blown away, leaving the ferric oxides exposed.

"They have accumulated in dark deposits at the bottom of sulphate cliffs,"
says Stephane Le Mouelic, Universite de Nantes, a member of the team who
performed the investigation. This suggests that the ferric oxides have been
uncovered by erosion before dropping to the base of the cliffs. The dunes in
this region are also enriched in ferric oxides.

Perhaps significantly, this phenomenon is not unique to the Aram Chaos
region. The NASA Opportunity rover discovered ferric oxide deposits in
Meridiani Planum, about 1000 km away. The scientists called the deposits
'blueberries', because of their spherical shape. Valles Marineris, 3000 km
away, also shows similar deposits. So Mars Express' detection of ferric
oxides in Aram Chaos links together widely separated areas of Mars.

There may even be other regions that have witnessed the same accumulation
process but now lie hidden from Mars Express' view. "OMEGA is sensitive to
the first hundreds of microns of the surface. So, a layer of Martian dust
just one millimetre thick will hide the signature from us," says Marion
Masse, Universite de Nantes, lead author on the paper describing these
results. Fortunately, in many regions of Mars, such as Aram Chaos, wind
erosion has blown the dust cover away, leaving bulk rocks exposed.

Although the true extent and nature of the accumulation process of sulphates
and ferric oxides remain elusive, the team are now investigating possible
hypotheses that could have caused it in the first place. At this stage, they
are ruling nothing out. It could be anything from atmospheric precipitation
such as rain or snow, to volcanic ashes or glacial deposits.

Note for editors:
 
The findings appear in the article 'Mineralogical composition, structure,
morphology, and geological history of Aram Chaos crater fill on Mars derived
from OMEGA Mars Express data,' by M. Masse et al., published in the Journal
of Geophysical Research (VOL. 113, E12006, doi:10.1029/2008JE003131).

For more information:
 
Stephane Le Mouelic
Universite de Nantes, France
Email: stephane.lemouelic _at_ univ-nantes.fr

Marion Masse
Universite de Nantes, France
Email: marion.masse _at_ univ-nantes.fr

Jean-Pierre Bibring, OMEGA Principal Investigator
Institut d'Astrophysique Spatiale - IAS, Orsay, France
Email : jean-pierre.bibring _at_ ias.u-psud.fr

Agustin Chicarro, ESA Mars Express Project Scientist
Email: Agustin.Chicarro _at_ esa.int

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Received on Mon 23 Mar 2009 07:25:08 PM PDT