0000000000223925
AUTHOR
R. Gellert
Mineralogy of volcanic rocks in Gusev Crater, Mars: Reconciling Mössbauer, Alpha Particle X-ray Spectrometer, and Miniature Thermal Emission Spectrometer spectra
Complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in Gusev Crater have been determined by modeling Mössbauer subspectral areas as mineral weight percentages, and combining those percentages with the proportions of iron-free minerals not detected by Mössbauer (normative plagioclase, apatite, and chromite, as calculated from Alpha Particle X-Ray Spectrometer (APXS) chemical analyses). Comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured Miniature Thermal Emission Spectrometer (Mini-TES) spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic pla…
Depth selective Mössbauer spectroscopy: Analysis and simulation of 6.4 keV and 14.4 keV spectra obtained from rocks at Gusev Crater, Mars, and layered laboratory samples
[1] The miniaturized Mossbauer spectrometer (MIMOS) II Mossbauer spectrometers on the Mars Exploration Rovers (MER) simultaneously obtained 6.4 keV and 14.4 keV Mossbauer spectra from rock and soil targets. Because photons with lower energy have a shallower penetration depth, 6.4 keV spectra contain more mineralogical information about the near-surface region of a sample than do 14.4 keV spectra. The influence of surface layers of varying composition and thickness on Mossbauer spectra was investigated by Monte Carlo simulation and by measurement using a copy of the MER MIMOS II instrument and samples with one or two layers of known thicknesses. Thin sections of minerals or metallic Fe foil …
Overview of the Opportunity Mars Exploration Rover Mission to Meridiani Planum: Eagle Crater to Purgatory Ripple
The Mars Exploration Rover Opportunity touched down at Meridiani Planum in January 2004 and since then has been conducting observations with the Athena science payload. The rover has traversed more than 5 km, carrying out the first outcrop-scale investigation of sedimentary rocks on Mars. The rocks of Meridiani Planum are sandstones formed by eolian and aqueous reworking of sand grains that are composed of mixed fine-grained siliciclastics and sulfates. The siliciclastic fraction was produced by chemical alteration of a precursor basalt. The sulfates are dominantly Mg-sulfates and also include Ca-sulfates and jarosite. The stratigraphic section observed to date is dominated by eolian bedfor…
Geochemical and mineralogical indicators for aqueous processes in the Columbia Hills of Gusev crater, Mars
[1] Water played a major role in the formation and alteration of rocks and soils in the Columbia Hills. The extent of alteration ranges from moderate to extensive. Five distinct rock compositional classes were identified; the order for degree of alteration is Watchtower ≅ Clovis > Wishstone ≅ Peace > Backstay. The rover's wheels uncovered one unusual soil (Paso Robles) that is the most S-rich material encountered. Clovis class rocks have compositions similar to Gusev plains soil but with higher Mg, Cl, and Br and lower Ca and Zn; Watchtower and Wishstone classes have high Al, Ti, and P and low Cr and Ni; Peace has high Mg and S and low Al, Na, and K; Backstay basalts have high Na and K comp…
Nickel on Mars: Constraints on meteoritic material at the surface
[1] Impact craters and the discovery of meteorites on Mars indicate clearly that there is meteoritic material at the Martian surface. The Alpha Particle X-ray Spectrometers (APXS) on board the Mars Exploration Rovers measure the elemental chemistry of Martian samples, enabling an assessment of the magnitude of the meteoritic contribution. Nickel, an element that is greatly enhanced in meteoritic material relative to samples of the Martian crust, is directly detected by the APXS and is observed to be geochemically mobile at the Martian surface. Correlations between nickel and other measured elements are used to constrain the quantity of meteoritic material present in Martian soil and sedimen…
Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills
The Moessbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe-bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater. Eight Fe-bearing phases were identified: olivine, pyroxene, ilmenite, magnetite, nanophase ferric oxide (npOx), hematite, goethite, and a Fe(3+)-sulfate. Adirondack basaltic rocks on the plains are nearly unaltered (Fe(3+)/Fe(sub T) Px), and minor npOx and magnetite. Columbia Hills basaltic rocks are nearly unaltered (Peace and Backstay), moderately altered (WoolyPatch, Wishstone, and Keystone), and pervasively altered (e.g., Clovis, Uchben, Watchtower, …
Mineralogy and chemistry of cobbles at Meridiani Planum, Mars, investigated by the Mars Exploration Rover Opportunity
Numerous loose rocks with dimensions of a few centimeters to tens of centimeters and with no obvious physical relationship to outcrop rocks have been observed along the traverse of the Mars Exploration Rover Opportunity. To date, about a dozen of these rocks have been analyzed with Opportunity’s contact instruments, providing information about elemental chemistry (Alpha Particle X‐ray Spectrometer), iron mineralogy and oxidation states (Mossbauer Spectrometer) and texture (Microscopic Imager). These "cobbles" appear to be impact related, and three distinct groups can be identified on the basis of chemistry and mineralogy. The first group comprises bright fragments of the sulfate‐rich bedroc…
Spirit Mars Rover Mission to the Columbia Hills, Gusev Crater: Mission overview and selected results from the Cumberland Ridge to Home Plate
This paper summarizes the Spirit rover operations in the Columbia Hills of Gusev Crater from sols 513 to 1476 and provides an overview of selected findings that focus on synergistic use of the Athena Payload and comparisons to orbital data. Results include discovery of outcrops (Voltaire) on Husband Hill that are interpreted to be altered impact melt deposits that incorporated local materials during emplacement. Evidence for extensive volcanic activity and aqueous alteration in the Inner Basin is also detailed, including discovery and characterization of accretionary lapilli and formation of sulfate, silica, and hematite-rich deposits. Use of Spirit's data to understand the range of spectra…
Exploration of Victoria Crater by the Mars Rover Opportunity
“Lake” Victoria? After having explored the Eagle and Endurance craters, which are separated by only 800 meters, the Mars Exploration Rover Opportunity spent 2 years at Victoria, a much larger impact crater located 6 kilometers south across Meridiani Planum. Sedimentary rocks previously analyzed at Eagle and Endurance point to local environmental conditions that included abundant liquid water in the ancient past. Now, an analysis of rocks in the walls of Victoria by Squyres et al. (p. 1058 ) reveals that the aqueous alteration processes that operated at Eagle and Endurance also acted at Victoria. In addition, sedimentary layering in the crater walls preserves evidence of ancient windblown du…
Spirit Mars Rover Mission: Overview and selected results from the northern Home Plate Winter Haven to the side of Scamander crater
Spirit Mars Rover Mission : Overview and selected results from the northern Home Plate Winter Haven to the side of Scamander crater
Alpha Particle X-Ray Spectrometer (APXS): Results from Gusev crater and calibration report
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 Col…