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Author(s): Kevin M. Cannon (corresponding author) [1, 2]; Stephen W. Parman [1]; John F. Mustard [1] On Mars, clay minerals are widespread in terrains that date back to the Noachian [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2010.06.001 Byline: James J. Wray (a), Steven W. Squyres (a), Leah H. Roach (b), Janice L. Bishop (c), John F. Mustard (d), Eldar Z. Noe Dobrea (e) Keywords: Mars, Surface; Mineralogy; Spectroscopy Abstract: The region surrounding the Mawrth Vallis outflow channel on Mars hosts thick layered deposits containing diverse phyllosilicate minerals. Here we report detection of the Ca-sulfate bassanite on the outflow channel floor, requiring a more complex aqueous chemistry than previously inferred for this region. The sulfate-bearing materials underlie phyllosilicate-bearing strata, and provide an opportunity for testing proposed models of martian geochemical evolution with a future landed mission. Author Affiliation: (a) Department of Astronomy, Cornell University, Ithaca, NY 14853, USA (b) Frontier Technology, Inc., 100 Cummings Center, Suite 450G, Beverly, MA 01915, USA (c) Carl Sagan Center, SETI Institute, Mountain View, CA 94043, USA (d) Department of Geological Sciences, Brown University, Providence, RI 02912, USA (e) Planetary Science Institute, 1700 E. Fort Lowell Rd., Suite 106, Tucson, AZ 85719, USA Article History: Received 27 February 2010; Revised 29 May 2010; Accepted 1 June 2010

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.11.029 Byline: Leah H. Roach (a), John F. Mustard (a), Melissa D. Lane (b), Janice L. Bishop (c), Scott L. Murchie (d) Keywords: Mars, Surface; Spectroscopy; Mineralogy Abstract: Previous orbital mapping of crystalline gray haematite, ferric oxides, and sulfates has shown an association of this mineralogy with light-toned, layered deposits on the floor of Valles Marineris, in chaos terrains in the canyon's outflow channels, and in Meridiani Planum. The exact nature of the relationship between ferric oxides and sulfates within Valles Marineris is uncertain. The Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite (OMEGA) spectrometer initially identified sulfate and ferric oxides in the layered deposits of Valles Marineris. The Thermal Emission Spectrometer (TES) has also mapped coarse (gray) haematite in or at the base of these deposits. We use Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectra and Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) imagery from the Mars Reconnaissance Orbiter (MRO) to explore the mineralogy and morphology of the large layered deposit in central Capri Chasma, part of the Valles Marineris canyon system that has large, clear exposures of sulfate and haematite. We find kieserite (MgSO.sub.4*H.sub.2O) and ferric oxide (often crystalline red haematite) in the lower bedrock exposures and a polyhydrated sulfate without ferric oxides in the upper bedrock. This stratigraphy is duplicated in many other basinal chasmata, suggesting a common genesis. We propose the haematite and monohydrated sulfate formed by diagenetic alteration of a sulfate-rich sedimentary deposit, where the upper polyhydrated sulfate-rich, haematite-poor layers either were not buried sufficiently to convert to a monohydrated sulfate or were part of a later depositional phase. Based on the similarities between the Valles Marineris assemblages and the sulfate and haematite-rich deposits of Meridiani Planum, we hypothesize a common evaporite and diagenetic formation process for the Meridiani Planum sediments and the sulfate-bearing basinal Interior Layered Deposits. Author Affiliation: (a) Dept. Geological Sciences, Brown University, 324 Brook St., Providence, RI 02912, USA (b) Planetary Science Institute, 1700 E. Fort Lowell Rd., Suite 106, Tucson, AZ 85719, USA (c) The SETI Institute & NASA-Ames Research Center, Carl Sagan Center, 515 N. Whisman Rd., Mountain View, CA 94043, USA (d) Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA Article History: Received 8 May 2009; Revised 26 October 2009; Accepted 20 November 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.09.003 Byline: Leah H. Roach (a), John F. Mustard (a), Gregg Swayze (b), Ralph E. Milliken (c), Janice L. Bishop (d), Scott L. Murchie (e), Kim Lichtenberg (f) Keywords: Mars, Surface; Spectroscopy Abstract: New high-resolution spectral and morphologic imaging of deposits on walls and floor of Ius Chasma extend previous geomorphic mapping, and permit a new interpretation of aqueous processes that occurred during the development of Valles Marineris. We identify hydrated mineralogy based on visible-near infrared (VNIR) absorptions. We map the extents of these units with CRISM spectral data as well as morphologies in CTX and HiRISE imagery. Three cross-sections across Ius Chasma illustrate the interpreted mineral stratigraphy. Multiple episodes formed and transported hydrated minerals within Ius Chasma. Polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma. They may have been precipitates in a closed basin or diagenetically altered after deposition. Fluvial or aeolian processes then deposited layered Fe/Mg smectite and hydrated silicate on the chasma floor, postdating the sulfates. The smectite apparently was weathered out of Noachian-age wallrock and transported to the depositional sites. The overlying hydrated silicate is interpreted to be an acid-leached phyllosilicate transformed from the underlying smectite unit, or a smectite/jarosite mixture. The finely layered smectite and massive hydrated silicate units have an erosional unconformity between them, that marks a change in surface water chemistry. Landslides transported large blocks of wallrock, some altered to contain Fe/Mg smectite, to the chasma floor. After the last episode of normal faulting and subsequent landslides, opal was transported short distances into the chasma from a few m-thick light-toned layer near the top of the wallrock, by sapping channels in Louros Valles. Alternatively, the material was transported into the chasma and then altered to opal. The superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential, distinct aqueous environments, characterized by alkaline, then circum-neutral, and finally very acidic surface or groundwater chemistry. Author Affiliation: (a) Dept. Geological Sciences, Brown University, 324 Brook St., Providence, RI 02912, USA (b) US Geological Survey, Branch of Geophysics, Box 25046, MS 964, Denver Federal Center, Denver, CO 80225, USA (c) Jet Propulsion Laboratory, MS 183-30, 4800 Oak Grove Dr., Pasadena, CA 91109, USA (d) The SETI Institute and NASA-Ames Research Center, Carl Sagan Center, 515 N. Whisman Rd., Mountain View, CA 94043, USA (e) Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA (f) Dept. Earth and Planetary Sciences, Washington University in St. Louis, 1 Brookings Dr., Box 1169, St. Louis, MO 63130, USA Article History: Received 8 May 2009; Revised 15 August 2009; Accepted 7 September 2009

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 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 C[O.sub.2] absorption in the [H.sub.2]O ice bands at wavelengths near 2.0 [micro]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. This will allow a second level of refinement in the atmospheric and thermal correction of CRISM multispectral data. Index Terms--Atmospheric propagation, infrared spectroscopy, remote sensing, software verification and validation.

To better understand how terrestrial vegetative ecosystems respond to climate and/or anthropogenic effects, the scientific community is increasingly interested in developing methods of employing satellite data to track changes in land surface phenology (e.g., timing and rate of green-up, amplitude and duration of growing season, and timing and rate of senescence of plant classes). By increasing the inherent resolution of signal extraction procedures while minimizing the effects of cloud cover and prolonged data gaps, such tools can significantly improve land cover classification and land cover change monitoring on multiple scales. This report describes an intuitive approach for tracking the intra-annual details and interannual variability of multiyear time series, employing a sequence of annual high-order polynomial splines (up to the 14th order), stabilized by minimizing model roughness and weighted to fit the upper data envelope to minimize cloud cover bias. The algorithm is tested using multiyear time series for three very different classes of vegetation-stable agriculture, high elevation montane shrubland, and semiarid grassland with high interanuual variability. The results accurately track both short--and long-term land surface phenology and illustrate a robust potential for extracting temporal and spatial detail from a variety of satellite-based multiyear vegetation signals. Index Terms--Advanced Very High Resolution Radiometer (AVHRR), Fourier analysis, harmonic series, multiyear, normalized difference vegetation index (NDVI ), phenology, polynomial lit, signal processing, spline, time series.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.12.028 Byline: Ralph E. Milliken, John F. Mustard Keywords: Spectroscopy Abstract: Visible-near infrared reflectance spectra for five particle size fractions of a Hawaiian palagonite (HWMK101) and a nontronite (ferruginous smectite, Clay Minerals Society source clay SWa-1) were measured under ambient, purged, and heated conditions to characterize the effects of surface and volume scattering on the relationship between absolute H.sub.2O content and the strength of the 3 [mu]m absorption feature. Both materials were ground and dry sieved to particle sizes of Author Affiliation: Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912, USA Article History: Received 21 July 2006; Revised 30 November 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.10.025 Byline: Lisa C. Kanner, John F. Mustard, Aline Gendrin Keywords: Infrared observations; Mars; surface; Mineralogy; Spectroscopy Abstract: We investigate the ability to refine pyroxene composition and modal abundance from laboratory and remotely acquired spectra. Laboratory data including the martian meteorites, Shergotty, Zagami, MIL03346, and ALH84001 as well as additional pyroxene-rich spectra obtained from the OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite) spectrometer for Mars are characterized using the Modified Gaussian Model (MGM), a spectral deconvolution method developed by Sunshine et al. [Sunshine, J.M., Pieters, C.M., Pratt, S., 1990. J. Geophys. Res. 95, 6955-6966]. We develop two sensitivity tests to assess the extent to which the MGM can consistently predict (1) pyroxene composition and (2) modal abundance for a compositionally diverse suite of pyroxene spectra. Results of the sensitivity tests indicate that the MGM can be appropriately applied to remote spectroscopic measurements of extraterrestrial surfaces and can estimate pyroxene composition and relative abundance within a derived uncertainty. Deconvolved band positions for laboratory spectra of the meteorites Shergotty and Zagami are determined within [+ or -]17 nm while remotely acquired OMEGA spectra are defined within [+ or -]50 nm. These results suggest that absolute compositions can be uniquely derived from laboratory pyroxene-rich spectra and non-uniquely derived from the remote measurements of OMEGA at this time. While relative pyroxene chemistries are not assessed from OMEGA measurements at this time, relative pyroxene abundances are estimated using a normalized band strength ratio between the low-calcium (LCP) and high-calcium (HCP) endmember components and are constrained to [+ or -]10%. The fraction of LCP in a two-pyroxene mixture is the derived value from the normalized band strength ratio, LCP/(LCP+HCP). This calculation for relative abundance is robust in the presence of up to 10-15% olivine. Deconvolution results from the OMEGA spectra indicate that the ancient terrain in the Syrtis Major region is uniquely enriched in LCP (59[+ or -]10% LCP) relative to HCP while the volcanics of Syrtis Major are uniquely enriched in HCP (39[+ or -]10% LCP). Author Affiliation: Department of Geological Sciences, Brown University, 324 Brook Street, Box 1846, Providence, RI 02912, USA Article History: Received 24 May 2006; Revised 25 September 2006

A suite of sulfate minerals were characterized spectrally, compositionally, and structurally in order to develop spectral reflectance-compositional-structural relations for this group of minerals. Sulfates exhibit diverse spectral properties, and absorption-band assignments have been developed for the 0.3-26 [micro]m range. Sulfate absorption features can be related to the presence of transition elements, OH, [H.sub.2]O, and S[O.sub.4] groups. The number, wavelength position, and intensity of these bands are a function of both composition and structure. Cation substitutions can affect the wavelength positions of all major absorption bands. Hydroxo-bridged [Fe.sup.3+] results in absorption bands in the 0.43, 0.5, and 0.9 [micro]m regions, while the presence of [Fe.sup.2+] results in absorption features in the 0.9-1.2 [micro]m interval. Fundamental S-O bending and stretching vibration absorption bands occur in the 8-10, 13-18, and 19-24 [micro]m regions (1000-1250, 550-770, and 420-530 [cm.sup.- 1]). The most intense combinations and overtones of these fundamentals are found in the 4-5 [micro]m (2000-2500 [cm.sup.-1]) region. Absorption features seen in the 1.7-1.85 [micro]m interval are attributable to H-OH/O-H bending and translation/rotation combinations, while bands in the 2.1-2.7 [micro]m regions can be attributed to [H.sub.2]O- and OH-combinations as well as overtones of S-O bending fundamentals. OH- and [H.sub.2]O-bearing sulfate spectra are fundamentally different from each other at wavelengths below ~6 [micro]m. Changes in [H.sub.2]O/OH content can shift S-O band positions due to change in bond lengths and structural rearrangement. Differences in absorption band wavelength positions enable discrimination of all the sulfate minerals used in this study in a number of wavelength intervals. Of the major absorption band regions, the 4-5 [micro]m region seems best for identifying and discriminating sulfates in the presence of other major rock-forming minerals. Keywords: Asteroids, composition; Europa; Mars, surface; Meteorites; Mineralogy; Spectroscopy