[Baps] CfA Colloquium: Andy Knoll/Mars/Th. Sept 8

[Sarah T. Stewart-Mukhopadhyay]

http://www.cfa.harvard.edu/cfa/calendar/latest.html

Harvard Astronomy Colloquium
4 PM THURSDAY, SEPTEMBER 8
"Opportunity, Meridiani, and the Search for Life on Mars"
Prof. Andrew Knoll
Department of Earth and Planetary Sciences, Harvard.
Preceded by tea at 3:30 pm. Phillips Auditorium. 

Abstract: The MER rover opportunity has carried out the first outcrop-scale
investigation of ancient sedimentary rocks on Mars. The rocks, exposed in
craters and along fissures in Meridiani Planum, are sandstones formed via
the erosion and re-deposition of fine grained siliciclastics and evaporites
derived from the chemical weathering of olivine basalts by acidic waters. A
stratigraphic section more than seven meters thick measured in Endurance
crater is dominated by eolian dune and sand sheet facies; the uppermost half
meter, however, exhibits festoon cross lamination at a length scale that
indicates subaqueous deposition, likely in a playa-like interdune setting.
Silicates and sulfate minerals dominate outcrop geochemistry, but hematite
and Fe3D3 (another ferric iron phase) make up as much as 11% of the rocks by
weight. Jarosite in the outcrop matrix indicates precipitation at low pH.
Cements, hematitic concretions, and crystal molds attest to a complex
history of early diagenesis, mediated by ambient ground waters. The
depositional and early diagenetic paleoenvironment at Meridiani was arid,
acidic, and oxidizing, a characterization that places strong constraints on
astrobiologial inference. 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.mit.edu/pipermail/baps/attachments/20050904/cb5335b4/attachment.htm