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Dirt and Hematite on Mars

Dirt and Hematite on Mars. Remotely sensed compositional studies of surface materials and their links to the history of water on Mars. Amy Trueba Knudson Associate Research Scientist Planetary Science Institute August 2007 Retreat. Research Focus.

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Dirt and Hematite on Mars

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  1. Dirt and Hematite on Mars • Remotely sensed compositional studies of surface materials and their links to the history of water on Mars Amy Trueba Knudson Associate Research Scientist Planetary Science Institute August 2007 Retreat

  2. Research Focus • Mars Exploration Rover Mission, Miniature Thermal Emission Spectrometer (Mini-TES) • Spirit ‘soil’ composition • Observations from Opportunity • Mirror dust correction • Comprehensive compositional examination of dataset • The role of water in the formation of Valles Marineris interior layered deposits through mineral mapping • Mapped hematite deposits using TES data; characterized mineralogy and geologic context with multiple datasets • Detailed evaluation of the relationship of hematite to hydrated sulfates with high resolution views from HiRISE and coordinated mineralogy from CRISM

  3. “Spirit” rover observations of particulate “soils” 50 km 10 km

  4. Mirror dust and correction • Use a radiative transfer approach to model transmissive loss through dust on pointing mirror as well as emission from dust at temperature of mirror, after Smith et. al. [2002] • Works quite well on ‘Spirit’, have many of dusty targets to use for comparison and calibration • Correction is not quite as simple at Opportunity due to more variable dust change on mirror, but careful fitting to data should allow this approach to be applied successfully Ruff et. al (2006)

  5. Basaltic soils covered with a layer of fine dust • Soils at Gusev crater are predominantly a mixture of dust and fine grained (<~100 µm) sand • Disturbed soil composition is homogenous throughout 1100 sols of traverse, with the following exceptions: • Olivine abundances vary from ~10% to 30% • Bright Ca or Fe3+ sulfate-rich soils in isolated locations • Fine-grained < ~100 µm sand is basaltic in composition with a mineral assemblage including:

  6. Courtesy Ray Arvidson, Wash U. Endurance Crater Landing Site Erebus Victoria Crater 5 km 29

  7. Science questions at Meridiani Planum • Extent of hydration of outcrop rock • CRISM and TES do not detect hydrated minerals but Mini-TES indicates hydration features in fine-grained RAT tailings • Composition of unique targets • Cobbles - basaltic or meteoritic? • Pebble fields - potential source of sand? • Variability of composition of plains surfaces through traverse • Changes in hematite abundance (Mini-TES specialty!) • Variations in the basaltic sand component • Outcrop rock variability • Stratigraphy (?) • Ground truth for comparison to orbital datasets

  8. Apparent disconnect between Mössbauer, Mini-TES, and orbital vis/nir data (OMEGA, CRISM) • MTES and MB indicate moderate amounts of olivine (~10-25%) that varies across the traverse • CRISM and OMEGA detect very little to no olivine

  9. Hematite on Mars • Hematite was first identified at Terra Meridiani and then at Aram Chaos and in small areas of Valles Marineris [Christensen et al., 2000, 2001]. • Hematite formation on Mars may involve liquid water[e.g. Christensen et al., 2000; 2001, Chan et al., 2004, Squyres et al., 2004] but could also be the product of oxidation of iron minerals at high temperatures, such as in volcanic deposits [e.g. Arvidson et al., 2003, Noreen, et al., 2000] • Associated with Ca or Mg sulfates in all hematite localities [Gendrin et al., 2005]along with jarosite at Meridiani Planum, indicative of acid sulfate systems [e.g. Burns, 1987]

  10. Valles Marineris hematite exposures

  11. Hematite concentrations within Valles Marineris • Hematite is associated with low albedo surfaces adjacent to interior layered, light-toned deposits, or in some locations, within the layered materials. • There is little to no elevation trend to the hematite concentrations in Central Valles, more so in Capri Chasma. However, hematite is consistently situated near the base of layered materials overlying canyon floor materials. • Central deposits have characteristics indicative of lag deposits, with gravity driven separation from friable layered deposit materials. Capri deposits have characteristics of in-place layered materials. • Localized hematite abundances within more extensive layered materials in both regions indicates localized formational processes. • Hematite is intermixed with dark basaltic material, but is located adjacent to the light-toned sulfates.

  12. HiRISE in E. Candor Chasma PSP_002142_1730 FRT00003D58

  13. The End

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