Overview of Mars surface geochemical diversity through Alpha Particle X-Ray Spectrometer data multidimensional analysis: First attempt at modeling rock alteration
Article first published online: 6 NOV 2008
Copyright 2008 by the American Geophysical Union.
Journal of Geophysical Research: Planets (1991–2012)
Volume 113, Issue E12, December 2008
How to Cite
2008), Overview of Mars surface geochemical diversity through Alpha Particle X-Ray Spectrometer data multidimensional analysis: First attempt at modeling rock alteration, J. Geophys. Res., 113, E12S34, doi:10.1029/2007JE003010., , , , , , , and (
- Issue published online: 6 NOV 2008
- Article first published online: 6 NOV 2008
- Manuscript Accepted: 31 JUL 2008
- Manuscript Revised: 4 MAR 2008
- Manuscript Received: 4 OCT 2007
 Principal component analysis and a hierarchical clustering method have been employed to describe and quantify the compositional variability of Martian rocks and soils measured by the Alpha Particle X-Ray Spectrometers onboard the Mars Exploration Rovers. A robust classification of samples emerges which defines distinct rock classes and sheds light on the petrogenetic relationships between rocks. This is particularly useful in the case of rocks from Gusev Crater, where significant chemical diversity is observed. This approach also highlights that compositional variability of rocks at Meridiani is dominated by variations in sulfur content; the relative proportions of other elements remaining approximately constant. For soils, variations in Fe concentration dominate because of the presence of hematite-rich “berry”-bearing samples. On the basis of this observation, a simple geochemical model of acid fog alteration of Martian basalts has been tested, assuming either equivalent alteration of all phases or preferential alteration of certain phases (thus taking into account kinetic considerations). The results show that for certain ranges of SO3/basalt, many of the compositional and mineralogical features measured at both sites may be explained. The secondary mineralogy and bulk rock compositions predicted by the model are broadly consistent with rock and soil compositions from Gusev and Meridiani, especially if the role of brine circulation and evaporation are considered. Although agreement is not perfect, comparison of observations and models argues in favor of variable interaction of the Martian surface with sour gas, explaining the high local abundance of sulfates, for example.