Publications (8)8.94 Total impact
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Article: Mapping Minerals on Mars with CRISM: Atmospheric and Photometric Correction for MRDR Map Tiles, Version 2, and Comparison to OMEGA
LPI Contributions. 03/2013; 1719:1581. -
Article: Extensive MRO CRISM observations of 1.27 µm O2 airglow in Mars polar night and their comparison to MRO MCS temperature profiles and LMD GCM simulations
Journal of Geophysical Research (Planets). 08/2012; 117. -
Article: MRO/CRISM Retrieval of Surface Lambert Albedos for Multispectral Mapping of Mars with DISORT-based Rad. Transfer Modeling: Phase 1 - Using Historical Climatology for Temperatures, Aerosol Opacities, & Atmo. Pressures
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ABSTRACT: We discuss the DISORT-based radiative transfer pipeline ('CRISM_LambertAlb') for atmospheric and thermal correction of MRO/CRISM data acquired in multispectral mapping mode (~200 m/pixel, 72 spectral channels). Currently, in this phase-one version of the system, we use aerosol optical depths, surface temperatures, and lower-atmospheric temperatures, all from climatology derived from Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) data, and surface altimetry derived from MGS Mars Orbiter Laser Altimeter (MOLA). The DISORT-based model takes as input the dust and ice aerosol optical depths (scaled to the CRISM wavelength range), the surface pressures (computed from MOLA altimetry, MGS-TES lower-atmospheric thermometry, and Viking-based pressure climatology), the surface temperatures, the reconstructed instrumental photometric angles, and the measured I/F spectrum, and then outputs a Lambertian albedo spectrum. The Lambertian albedo spectrum is valuable geologically since it allows the mineralogical composition to be estimated. Here, I/F is defined as the ratio of the radiance measured by CRISM to the solar irradiance at Mars divided by $\pi$. After discussing the capabilities and limitations of the pipeline software system, we demonstrate its application on several multispectral data cubes: the outer northern ice cap of Mars, Tyrrhena Terra, and near the landing site for the Phoenix mission. For the icy spectra near the northern polar cap, aerosols need to be included in order to properly correct for the CO_2 absorption in the H_{2}O ice bands at wavelengths near 2.0 $\mu$m. In future phases of software development, we intend to use CRISM data directly in order to retrieve the spatiotemporal maps of aerosol optical depths, surface pressure and surface temperature.04/2009; -
Article: Compact Reconnaissance Imaging Spectrometer for Mars observations of northern Martian latitudes in summer
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ABSTRACT: 1] This paper brings together initial results obtained of the high northern latitudes in Mars years 28 and 29, between October 2006 and October 2008. These measurements confirm many previous models and shed new light on the nature of polar surface materials, particularly in intermediate-albedo units of the polar layered deposits, many of which are found to be ice-rich. We identify hydrated non ice materials present in many low-albedo troughs, as well as in the circumpolar erg that was previously associated with gypsum. We identify icy outlier deposits that may be related to subsurface thermophysical properties and permafrost. New observations of the gypsum-rich dune material constrain models for its formation and distribution. Intrinsic properties of ice content and grain size are found to be independent of the albedo of fine layered units and may provide a novel method for stratigraphic identification and correlation.J. Geophys. Res. 01/2009; 114:0-11. -
Article: The CRISM Investigation and Data Set from the Mars Reconnaissance Orbiter's Primary Science Phase
Journal of Geophysical Research 01/2009; 114(E00D07). · 3.02 Impact Factor -
Article: MRO/CRISM Retrieval of Surface Lambert Albedos for Multispectral Mapping of Mars With DISORT-Based Radiative Transfer Modeling: Phase 1—Using Historical Climatology for Temperatures, Aerosol Optical Depths, and Atmospheric Pressures
[show abstract] [hide abstract]
ABSTRACT: We discuss the DISORT-based radiative transfer pipeline (ldquoCRISM_LambertAlbrdquo) for atmospheric and thermal correction of MRO/CRISM data acquired in multispectral mapping mode (~200 m/pixel, 72 spectral channels). Currently, in this phase-one version of the system, we use aerosol optical depths, surface temperatures, and lower atmospheric temperatures, all from climatology derived from Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) data and from surface altimetry derived from MGS Mars Orbiter Laser Altimeter (MOLA). The DISORT-based model takes the dust and ice aerosol optical depths (scaled to the CRISM wavelength range), the surface pressures (computed from MOLA altimetry, MGS-TES lower atmospheric thermometry, and Viking-based pressure climatology), the surface temperatures, the reconstructed instrumental photometric angles, and the measured I/F spectrum as inputs, and then a Lambertian albedo spectrum is computed as the output. The Lambertian albedo spectrum is valuable geologically because it allows the mineralogical composition to be estimated. Here, I/F is defined as the ratio of the radiance measured by CRISM to the solar irradiance at Mars divided by pi; if there was no martian atmosphere, I/F divided by the cosine of the incidence angle would be equal to the Lambert albedo for a Lambertian surface. After discussing the capabilities and limitations of the pipeline software system, we demonstrate its application on several multispectral data cubes-particularly, the outer reaches of the northern ice cap of Mars, the Tyrrhena Terra area that is northeast of the Hellas basin, and an area near the landing site for the Phoenix mission in the northern plains. For the icy spectra near the northern polar cap, aerosols need to be included in order to properly correct for the CO<sub>2</sub> absorption in the H<sub>2</sub>O ice bands at wavelengths near 2.0 mum. In future phases of software development, we intend to use CRISM data directly in order t- - o retrieve the spatiotemporal maps of aerosol optical depths, surface pressure, and surface temperature. This will allow a second level of refinement in the atmospheric and thermal correction of CRISM multispectral data.IEEE Transactions on Geoscience and Remote Sensing 01/2009; · 2.89 Impact Factor -
Article: Discovery of the Acid-Sulfate Mineral Alunite in Terra Sirenum, Mars, Using MRO CRISM: Possible Evidence for Acid-Saline Lacustrine Deposits?
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ABSTRACT: CRISM spectral data collected over an unnamed 70-km-diameter impact crater in the Noachian-age southern highlands of Terra Sirenum (30°S, 158°W), Mars, indicate the presence of the acid-sulfate mineral alunite [KAl3(SO4)2(OH)6], based on diagnostic absorptions at NIR wavelengths. The USGS Tetracorder spectral shape-matching system was used to create color-coded maps of the distribution of IR-active mineral phases on the Martian surface. These maps indicate that a discontinuous, 1-km-wide, several-km-long, SE-trending band of alunite-rich material grades laterally into materials spectrally dominated by kaolinite or halloysite, and montmorillonite or partially hydrated silica. These minerals are found in layered terrain near the SW crater wall. Lava flows cover portions of the crater floor and partially embay this layered terrain. Montmorillonite or partially hydrated silica is also present in ridged material located several kilometers east of the alunite zone. Meter-scale HiRISE data indicate that the alunite occurs in a high albedo layer that is tens of meters thick and is capped in places by a spectrally neutral material. Kaolinite or halloysite occurs in polygonally cracked materials reminiscent of desiccated sediments. The observed association of minerals is consistent with advanced-argillic alteration associated with relict high-temperature hydrothermal systems, but is also compatible with the mineralogy of low- temperature, acid-saline, evaporative lacustrine deposits. Recent research indicates that alunite's NIR spectral features can be used to determine the approximate temperature at which alunite forms. CRISM alunite spectra closely match spectra of low-temp. terrestrial lacustrine alunites, based on relatively weak vibrationally-coupled absorptions at 1.43, 1.76, 2.21, and 2.32 μm. Given the observed lack of inflow channels, it is likely that the alunite was deposited in a spring-fed lake that once covered the bottom of the crater. Alunite may have formed as an alteration product of basaltic material in contact with H2SO4-rich lake water. Although oxidation of sulfides or hydrothermal H2S requires oxygen to form H2SO4, the disporportionation of SO2 that condenses in water above volcanic vents does not require an external source of oxygen and is a more likely source of aqueous sulfate for the formation of the alunite. Exploration for evidence of past aquatic life should be considered.AGU Fall Meeting Abstracts. 11/2008; -1:04. -
Article: Geomorphologic and Mineralogic Characterization of the Northern Plains of Mars at the Phoenix Mission Candidate Landing Sites
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ABSTRACT: [1] A suite of remote sensing data is used to evaluate both geomorphology and mineralogy of the candidate landing sites for the 2007 Phoenix Mission. Three candidate landing site boxes are situated in the northern plains of Mars on the distal flank of Alba Patera in the region from 67°N to 72°N and from ∼230°E to 260°E. Geomorphology is mapped at subkilometer spatial scales using Thermal Emission Imaging System (THEMIS) visible and Mars Orbiter Laser Altimeter (MOLA) topographic data, supplemented by images from the High-Resolution Imaging Science Experiment (HiRISE) and Context Imager (CTX). Mineralogy and spectral properties are examined using Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) visible and near-infrared multispectral mapping and targeted hyperspectral data at ∼200 and ∼20 m/pixel, respectively. Geomorphic mapping supports the idea that terrains along the boundary between the Amazonian Scandia region and Vastitas Borealis marginal geologic units have undergone extensive modification. Intercrater plains are disrupted to form mesas and interlocking blocks, while irregular depressions and knobby terrain are consistent with erosion/subsidence and local deposition. Despite the varied morphology, the present-day surface is nearly homogeneous with spectral signatures dominated by nanophase iron oxides and basaltic sand and rocks, similar to that of the Gusev crater plains at the Mars Exploration Rover (MER) landing site. The compilation of geomorphic and spectral information for the candidate Phoenix landing sites provides a framework for the mission's in situ observations to be extrapolated to the northern plains as a whole.Journal of Geophysical Research 01/2008; 113(E00A13). · 3.02 Impact Factor
