Science report: "Orbital Identification of Carbonate-Bearing Rocks on Mars."

[RGClark]

Just heard this announced on my local TV news channel:

Orbital Identification of Carbonate-Bearing Rocks on Mars.
Bethany L. Ehlmann, John F. Mustard, Scott L. Murchie, Francois Poulet, Janice L. Bishop, Adrian J. Brown, Wendy M. Calvin, Roger N. Clark, David J. Des Marais, Ralph E. Milliken, Leah H. Roach, Ted L. Roush, Gregg A. Swayze, James J. Wray
Science 19 December 2008: Vol. 322. no. 5909, pp. 1828 - 1832.
http://www.sciencemag.org/cgi/conten...;322/5909/1828

Here's the NASA news release:

December 18, 2008
Scientists Find 'Missing' Mineral and Clues to Mars Mysteries.
http://marsprogram.jpl.nasa.gov/mro/...20081218a.html

This is the journal published report of some results announced at some recent conferences. I discussed before though that there were some discrepancies from a pure carbonate signature in the spectra:

http://www.bautforum.com/space-explo...fied-mars.html

I don't have access to the full paper in Science so I don't know if further analysis allowed them to pin down more strongly the carbonate signature.


Bob Clark

[JonClarke]

This is s a very exciting paper. I don't have it front of me so this is from memory.

The signature is composed of 80% magnesite and 10% olivine and nontronite. The olivine is probably from overlying sands.

Four possibilities are discusssed - sedimentary magnesite, groundwater alteration, weathering, and hydrothermal alteration. Hyforthermal alteration is thought unlikley because of the absence of high temperature minerals like serpentines.

If alteration (whether groundwater, weathering, or hydrothermal) the parent rock was probably an ultramafic. Regardless of mechanism, the rock is almost completely replaced.

The area is Hesperian, so this is quite late in the martian history (as currently understood) for such intense aqueous alternation.