Correspondence and least squares analyses of soil and rock compositions for the Viking Lander 1 and pathfinder landing sites

Correspondence analysis is a dual Q and R mode factor analysis that allows simultaneous visualization of relationships between normalized variables an d samples. The usefulness of the technique is first illustrated with an ana lysis of a simulated feldspar compositional data set and then applied to an alysis of patterns among variables and samples for compositions obtained fo r Viking Lander 1 soils and Pathfinder rocks and soils. For the Martian dat a the first two factors capture 90% of the variance. Data projected onto th e plane defined by these two factors fall within a mixing triangle defined by three geologically plausible end-members: basaltic shergottite, andesite , and a halide-kieserite evaporite. However, examination of data projected onto the second and third factors shows that the compositions are systemati cally displaced from the mixing triangle plane in the same general directio n as the Fe vector. Inclusion of a Fe oxide (e.g., hematite or maghemite) a s a reasonable fourth end-member forms a mixing tetrahedron that encapsulat es the data. Least squares mixing analysis of the data with these four end- members and the elemental suite measured at both landing sites (Si, Al, Ti, Fe, Mg, Ca, S, Cl) implies that aeolian dust on rocks is a physical mixtur e of basalt and andesite-derived materials in approximately equal proportio ns, soil components at the two landing sites are similar to each other and less basalt-like than the aeolian dust, and Viking 1 soils are more andesit e-rich than the Pathfinder soils.