Chemical composition of Martian fines

Abstract

Of the 21 samples acquired for the Viking X ray fluorescence spectrometer, 17 were analyzed to high precision. Compared to typical terrestrial continental soils and lunar mare fines, the Martian fines are lower in AI, higher in Fe, and much higher in S and CI concentrations. Protected fines at the two lander sites are almost indistinguishable, but concentration of the element S is somewhat higher at Utopia. Duficrust fragments, successfully acquired only at the Chryse site, invariably contained about 50% higher S than fines. No elements correlate positively with S, except CI and possibly Mg. A sympathetic variation is found among the triad Si, AI, Ca; positive correlation occurs between Ti and Fe. Sample vafiabilities are as great within a few meters as between lander locations (4500 km apart), implying the existence of a universal Martian regolith component of constant average composition. The nature of the source materials for the regolith fines must be mafic to ultramafic. INTRODUCTIONFor the first in situ analysis of the inorganic chemical composition of surface material on the planet Mars, miniature energy-dispersive X ray florescence spectrometers were designed to fit within an available space on the Viking lander. Spacecraft constraints upon configuration, deployment, mass, and heat sterilizability of the experiment package limited the instrument design. It was hoped that three to five Martian samples could be analyzed for about a dozen elements. Altogether 21 samples were delivered to the two instruments, and 15 elements were analyzed for in most samples. Descriptions of the instrument design have been published previously Toulmin et al., 1973;Clark et al., 1977]. Preliminary reports on analytical results at both landing sites were published soon after the initial data were received Baird et al., 1976]. In this paper, we present our findings for the major and minor element concentrations in all samples taken at the two landing sites. These are based upon extensive data correction procedures and upon laboratory simulations using a flight-qualified instrument identical to those on Mars, operated under Martian conditions of temperature, pressure, and atmospheric composition.

Chemical, multispectral, and textural constraints on the composition and origin of rocks at the Mars Pathfinder landing site

“…Like the rocks, the Pathfinder soils [Rieder et al, 1997a] are normalized to 98% total oxides. For comparison purposes, XRF analyses of Viking soils [Clark et al, 1982] have been normalized to 95.4% total oxides (98% minus the average Pattffmder soil value of Na20 + K20 = 2.6%, oxides which were below detection limits in the Viking data set). Table 4 Figures 13a and 14b).…”

Multispectral imaging from Mars Pathfinder

“…Analysis of the Bright Red Drift material by the APXS showed that it was chemically similar to the reddish drifts measured at the Viking landing sites (e.g., Clark et al, 1982), and it has since been shown to be chemically similar to the reddish drifts examined by the MER rovers (e.g., Rieder et al, 2004). IMP data indicated that this material lacked a well defined absorption in the 900 nm region.…”

Evidence for Martian electrostatic charging and abrasive wheel wear from the Wheel Abrasion Experiment on the Pathfinder Sojourner rover

“…Elemental analyses by means of an X-ray fluorescence spectrometer indicate a content of iron given as about 18% by weight of Fe203 in the Martian soil [Clark et al, 1982].…”