Alpha Particle X‐Ray Spectrometer (APXS): Results from Gusev crater and calibration report

Abstract

[1] The chemical composition of rocks and soils on Mars analyzed during the Mars Exploration Rover Spirit Mission was determined by X-ray analyses with the Alpha Particle X-Ray Spectrometer (APXS). Details of the data analysis method and the instrument calibration are presented. Measurements performed on Mars to address geometry effects and background contributions are shown. Cross calibration measurements among several instrument sensors and sources are discussed. An unintentional swap of the two flight instruments is evaluated. New concentration data acquired during the first 470 sols of rover Spirit in Gusev Crater are presented. There are two geological regions, the Gusev plains and the Columbia Hills. The plains contain soils that are very similar to previous landing sites on Mars. A meteoritic component in the soil is identified. Rocks in the plains revealed thin weathering rinds. The underlying abraded rock was classified as primitive basalt. One of these rocks contained significant Br that is probably associated with vein-filling material of different composition. One of the trenches showed large subsurface enrichments of Mg, S, and Br. Disturbed soils and rocks in the Columbia Hills revealed different elemental compositions. These rocks are significantly weathered and enriched in mobile elements, such as P, S, Cl, or Br. Even abraded rock surfaces have high Br concentrations. Thus, in contrast to the rocks and soils in the Gusev Plains, the Columbia Hills material shows more significant evidence of ancient aqueous alteration.

Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

“…Humphrey is inferred to contain plagioclase, pyroxene, and Fo52 with up to 10% highsilica glass . The weathering rind on Humphrey (McSween et al, 2004;Gellert et al, 2006) (Fig. 3) is modeled here because abrasion reached unaltered parent , and forward modeling relies upon knowledge of parent material.…”

Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration

“…Observations made over two years by multiple instruments consistently indicate that the east and west sides of Home Plate are (49) 339 (49) 349 (40) 478 (48) 420 (39) 362 (40) 310 (39) 395 (54) Zn 463 (21) 435 (22) 566 (16) 680 (21) 570 (15) 568 (16) 471 (15) 368 (22) Br 179 (20) 183 (20) 147 (16) 115 (16) 81 (15) 42 (15) 28 (15) 181 (23) Results are calibrated according to Gellert et al (2006) and are more fully presented by Ming et al (2008 different. The east side has more pyroxene, magnetite, and higher Al, Si/Mg, Zn, Ni, and K (e.g., Fig.…”

The evolution of a heterogeneous Martian mantle: Clues from K, P, Ti, Cr, and Ni variations in Gusev basalts and shergottite meteorites

“…F) TiO 2 vs. MgO. Data are from Anand et al (2008), Dreibus et al (2000Dreibus et al ( , 2002, Gellert et al (2006), Gillet et al (2005), Ikeda et al (2006), Jambon et al (2002), , Neal et al (2001), Rubin et al (2000), Shirai and Ebihara (2004), Taylor et al (2002), Treiman et al (1986), Warren et al (1996Warren et al ( , 1999. .…”