|
|
| Modal Mineralogy of the Martian Phyllosilicate-rich Terrains from the Mex/omega Reflectance Data |
| Presentation Time: Tuesday, 9:10 a.m. - 9:20 a.m. |
Francois Poulet1, J. Bibring1, V. Chevrier2, Y. Langevin1, B. Gondet1
1Institut d'Astrophysique Spatiale, Universite Paris IX, France, 2Arkansas Space Center. |
| Presentation Number: 14.05 |
Using classical methods of spectral identification based on the absorption band depth of minerals, OMEGA has provided an unambiguous identification of phyllosilicates on the surface of Mars (Poulet et al. 2005, Nature, 438). The presence of these minerals on Mars is of great exobiological relevance, because some of phyllosilicates are potential prebiotic catalyst. However, one of the significant challenges for the use of reflectance spectroscopy is the relationships between the band depth absorptions and mineral abundances and grain sizes.
The modal mineralogy (mineral abundances) of the phyllosilicate-rich terrains is derived using a nonlinear unmixing model based on the Shkuratov radiative transfer theory (Shkuratov et al. 1999, Icarus, 137). We focus our study on the two major regions where phyllosilicates were detected on Mars: Mawrth Vallis and Nilo-Syrtis. Significant differences between these two regions in mineral abundances are found. The phyllosilicate-rich outcrops in Mawrth Vallis are best reproduced by ~60% of phyllosilicates (nontronite, montmorillonite) mixed with hydroxides (Ferrihydrite as a likely end-member) and some non-phyllosilicate materials (plagioclase and Martian dust). In the NiloSyrtis region, the total abundance of the phyllosilicate minerals is significantly smaller than in Mawrth Vallis and mafic materials such as pyroxene are always required. This strongly suggests that the degree of alteration was stronger in Mawrth Vallis than anywhere on Mars. In the NiloSyrtis region, we observe significant spot-to-spot differences in modal mineralogy; these differences are remarkably consistent with the geomorphology. For instance, the floor of a crater is well reproduced by a mixture containing a low grade metamorphic water-bearing mineral. This unique mineralogy suggests that the impact may have played a role in the formation of this secondary mineral. Other implications for surface alteration will be addressed. |
| |
|
|
|
|
|
|
The Online Abstract Submission and Invitation System
© 1996 - 2010 Coe-Truman Technologies, Inc. All rights reserved.
|
|
|
|
|
|
