Skip to main content
U.S. flag

An official website of the United States government

Regional and grain size influences on the geochemistry of soil at Gusev Crater

July 1, 2010

Congruous with earlier work, Martian soil along the Spirit Rover's traverse at Gusev crater can be divided into three broad groups by size: fines (<150 μm), sand, and a mix of various grain sizes. The key chemical observation is greater homogeneity in fines relative to the other two, consistent with regional‐ and global‐scale sampling of chemical compositions by finer particle sizes. The mix class is generally more heterogeneous as are samples from the Columbia Hills within each class. Variation in the trace element Ni is consistent with a CI contribution not exceeding 3%, while that of Ti is compatible with Fe‐Ti oxide enrichment not exceeding 3%. Physical mixing models are poorly supported. Among many potential binary and three‐component mixing models, only two show some consistency with the soil data: typical fines with the opaline Si end‐member identified at Home Plate and typical fines with sulfates (bearing a variable mix of Ca, Fe, and Mg cations). We also infer that binary mixing transcends classes, contrasting strongly with terrestrial sediments, and that mixing trends are consistent with significant nonmixing contributions, perhaps including localized chemical alteration. The decoupling between chemistry and grain size classes also suggests that processes linking composition with grain size, such as heavy mineral sorting, may have been minimal or absent entirely. The primary exception to this is the correlation between Cl and Si, Cl‐S, and Al‐Si, which is strongest in the fines class.

Publication Year 2010
Title Regional and grain size influences on the geochemistry of soil at Gusev Crater
DOI 10.1029/2010JE003637
Authors Suniti Karunatillake, Scott M. McLennan, Kenneth E. Herkenhoff
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research E: Planets
Index ID 70201005
Record Source USGS Publications Warehouse
USGS Organization Astrogeology Science Center