Experimentelle und Analytische Planetologie
The meteoritic component on the surface of Mars: Implications for organic and inorganic geochemistry
Introduction: The mixing relationships, in particular the meteoritic contribution in the Martian soil were
determined by means of least squares analysis of chemical data from APXS-Mars-Pathfinder (MPF) [1] and
XRF-Viking [2] measurements. The soil composition may be represented as a mixture of the
MPF-soil free rock (SFR), primitive cosmic material (C1-chondrite), and physical weathering products of
MPF-andesites (PWP). Based on the component analysis, the composition of the Global Dust Unit and
constraints on trace element concentrations as well as the amount of putative organic matter are inferred.
Method and results: In
our least squares (LS) analysis 13 major elements were taken into account. The SFR and C1-chondrite compositions
were taken from [1] and [3], respectively. Prior to LS analysis a CIPW normative calculation was done on the SFR
chemistry. In analogy to Antarctic weathering scenarios, minerals with high susceptibility to physical disintegration
were assigned to a fraction of detritus PWP according to their normative ratios in parent andesites. To account for
the uncertainties inherent in analytical data from Mars, the individual element concentrations were weighted
accordingly. The convergence of the regression lines to a single point indicates the existence and the composition of
a Global Dust Unit (GDU). GDU material appears to be intimately admixed to MPF surface soils (~40
wght% C1) and also to Viking deep soil samples (~25 wght% C1). This is consistent with data in [4] and [5].
Some GDU material also appears to adhere to MPF rock samples. Implications:
Our analysis allows to estimate soil formation rates and trace element as well as organic matter abundances on Mars.
According to the inferred meteoritic contribution, 1.4 wght% C is missing in the Martian soil. Similarly, 0.4 wght%
Ni should be present in surface soils. This is more than APXS data would suggest. The discrepancy in Ni
concentrations might be due to secondary fluorescence effects. Alternative in-situ analytical techniques, such
as Laser-induced Plasma Spectroscopy (LIPS), may help to resolve this problem.
References: [1] Wänke H. et al. (2001) Space Sci. Rev. 96, 317-330. [2] Clark B. C. et al.
(1982) JGR 87, 10,059-10,067. [3] Wasson J. T. and Kallemeyn G. W. (1988) Phil. Trans. Roy. Soc.
A 325, 535-544. [4] Boslough M. B. (1988) LPS XIX, 120-121. [5] Flynn G. J. and McKay
D. S. (1990) JGR 95, 14,497-14,509.
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