Spectral characterization of weathering products of elemental iron in a Martian atmosphere: Implications for Mars hyperspectral studies

Research areas:
Year:
2006
Authors:
Journal:
PLANETARY AND SPACE SCIENCE
Volume:
54
Number:
11, SI
Pages:
1034-1045
Month:
September
ISSN:
0032-0633
BibTex:
Note:
General Assembly of the European-Union-of-Geosciences, Vienna, AUSTRIA, APR 24-29, 2005
Abstract:
Visible and near-infrared spectroscopic properties have been measured on
elemental iron experimentally weathered in simulated Martian atmosphere
and correlated to mineralogical compositions determined by X-ray
diffraction. Two main features are observed in the reflectance spectra,
corresponding to two deep bands located at 0.9 and 3.1 mu m,
respectively the iron band and the hydration band. In early weathering
stages both Fe(2+) and Fe(3+) bands are identified. In addition, whereas
the water band posit-on does not change with time, the Fe(2+) band
disappears, and the Fe(3+) band shifts towards longer wavelength (from
0.88 to 0.92 mu m) because of transition from Fe(2+) phases (siderite)
to Fe(3+) phases (ferrihydrite and goethite). Apart from these spectral
signatures, other bands more specific of each phase are not clearly
evidenced, especially for siderite. This is due to relatively low
abundance of siderite (< 20 wt\%), but also to the very small grain size
of secondary phase as well as surface coatings of iron (oxy)hydroxides.
Therefore, our results suggest that carbonates, even if not detected,
could be present in the form of very small grains in the surface of
Mars. (c) 2006 Elsevier Ltd. All rights reserved.