PO Box 344

Lovettsville, VA, United States

PO Box 344

Lovettsville, VA, United States
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Gerber F.,CNRS Paris Institute of Global Physics | Gerber F.,CEA DAM Ile-de-France | Marion R.,CEA DAM Ile-de-France | Olioso A.,French National Institute for Agricultural Research | And 3 more authors.
Remote Sensing of Environment | Year: 2011

Vegetation water content retrieval using passive remote sensing techniques in the 0.4-2.5 μm region (reflection of solar radiation) and the 8-14 μm region (emission of thermal radiation) has given rise to an abundant literature. The wavelength range in between, where the main water absorption bands are located, has surprisingly received very little attention because of the complexity of the radiometric signal that mixes both reflected and emitted fluxes. Nevertheless, it is now covered by the latest generation of passive optical sensors (e.g. SEBASS, AHS). This work aims at modeling leaf spectral reflectance and transmittance in the infrared, particularly between 3 μm and 5 μm, to improve the retrieval of vegetation water content using hyperspectral data. Two unique datasets containing 32 leaf samples each were acquired in 2008 at the USGS National Center, Reston (VA, USA) and the ONERA Research Center, Toulouse (France). Reflectance and transmittance were recorded using laboratory spectrometers in the spectral region from 0.4 μm to 14 μm, and the leaf water and dry matter contents were determined. It turns out that these spectra are strongly linked to water content up to 5.7 μm. This dependence is much weaker further into the infrared, where spectral features seem to be mainly associated with the biochemical composition of the leaf surface. The measurements show that leaves transmit light in this wavelength domain and that the transmittance of dry samples can reach 0.35 of incoming light around 5 μm, and 0.05 around 11 μm. This work extends the PROSPECT leaf optical properties model by taking into account the high absorption levels of leaf constituents (by the insertion of the complex Fresnel coefficients) and surface phenomena (by the addition of a top layer). The new model, PROSPECT-VISIR (VISible to InfraRed), simulates leaf reflectance and transmittance between 0.4 μm and 5.7 μm (at 1. nm spectral resolution) with a root mean square error (RMSE) of 0.017 and 0.018, respectively. Model inversion also allows the prediction of water (RMSE = 0.0011. g/cm2) and dry matter (RMSE = 0.0013. g/cm2) contents. © 2010 Elsevier Inc.

Thomson B.J.,The Johns Hopkins Applied Physics Laboratory | Bridges N.T.,The Johns Hopkins Applied Physics Laboratory | Milliken R.,University of Notre Dame | Baldridge A.,Planetary Science Institute | And 6 more authors.
Icarus | Year: 2011

Gale Crater contains a 5.2. km-high central mound of layered material that is largely sedimentary in origin and has been considered as a potential landing site for both the MER (Mars Exploration Rover) and MSL (Mars Science Laboratory) missions. We have analyzed recent data from Mars Reconnaissance Orbiter to help unravel the complex geologic history evidenced by these layered deposits and other landforms in the crater. Results from imaging data from the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) confirm geomorphic evidence for fluvial activity and may indicate an early lacustrine phase. Analysis of spectral data from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument shows clay-bearing units interstratified with sulfate-bearing strata in the lower member of the layered mound, again indicative of aqueous activity. The formation age of the layered mound, derived from crater counts and superposition relationships, is ∼3.6-3.8. Ga and straddles the Noachian-Hesperian time-stratigraphic boundary. Thus Gale provides a unique opportunity to investigate global environmental change on Mars during a period of transition from an environment that favored phyllosilicate deposition to a later one that was dominated by sulfate formation. © 2011 Elsevier Inc.

Williamson T.E.,New Mexico Museum of Natural History and Science | Weil A.,Oklahoma State University | Standhardt B.,P.O. Box 344
Journal of Vertebrate Paleontology | Year: 2011

Cimolestids are a minor component of early Paleocene (Puercan) faunas of western North America. Here we report on cimolestids from the early Paleocene (middle and late Puercan; Pu2-3) of the Nacimiento Formation, San Juan Basin, New Mexico. New specimens of Puercolestes simpsoni include portions of the deciduous and lower dentition not previously known. We conclude that Genus B of Van Valen is probably conspecific with this taxon. Two new genera and species, Chacopterygus minutus and Betonnia tsosia, are from the Pu2 and Pu2-Pu3, respectively. One additional unnamed taxon is based on isolated teeth from Pu2-3 localities. A phylogenetic analysis indicates that Puercolestes simpsoni is sister to Cimolestes. Chacopterygus minutus, Betonnia tsosia, and the unnamed cimolestid form a polytomy that is sister to Procerberus. This resulting clade is sister to Batodon + Maelestes. The results of this analysis suggest that P. simpsoni is descended from Cretaceous taxa of western North America. The origins of other early Paleocene cimolestids from either Asia or North America is equivocal. The species diversity of Cimolestidae in the Puercan of New Mexico and other Puercan localities of western North America is similar to that of latest Cretaceous (Lancian) faunas of the northern Rocky Mountain Region. © 2011 by the Society of Vertebrate Paleontology.

Brown A.J.,Search for Extraterrestrial Intelligence Institute | Hook S.J.,Jet Propulsion Laboratory | Baldridge A.M.,Jet Propulsion Laboratory | Crowley J.K.,P.O. Box 344 | And 5 more authors.
Earth and Planetary Science Letters | Year: 2010

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has returned observations of the Nili Fossae region indicating the presence of Mg-carbonate in small (<10km sq2), relatively bright rock units that are commonly fractured (Ehlmann et al., 2008b). We have analyzed spectra from CRISM images and used co-located HiRISE images in order to further characterize these carbonate-bearing units. We applied absorption band mapping techniques to investigate a range of possible phyllosilicate and carbonate minerals that could be present in the Nili Fossae region. We also describe a clay-carbonate hydrothermal alteration mineral assemblage in the Archean Warrawoona Group of Western Australia that is a potential Earth analog to the Nili Fossae carbonate-bearing rock units. We discuss the geological and biological implications for hydrothermal processes on Noachian Mars. © 2010 Elsevier B.V.

Marion G.M.,Desert Research Institute | Kargel J.S.,University of Arizona | Crowley J.K.,P.O. Box 344 | Catling D.C.,University of Washington
Icarus | Year: 2013

Mars volcanic SO2 and H2S gas emissions are likely the dominant source of martian sulfate, and the source of sulfuric acid. Until this work, the FREZCHEM model lacked SO2 and H2S gases and associated sulfite and sulfide minerals. The specific objectives of this paper were to add these components and associated sulfite and sulfide minerals and phases into FREZCHEM, and to explore some possible roles of these chemistries on Mars. New solid phases added included the sulfites: Na2SO3·7H2O, K2SO3, (NH4)2SO3·H2O, MgSO3·6H2O, CaSO3·0.5H2O, and FeSO3·1.5H2O, and the sulfide: FeS2. The lowest eutectic of these minerals was K2SO3 (= 6.57m) at 228K. Because sulfurous acid is stronger than carbonic acid, this causes a much larger fraction of S(IV) to exist as sulfite (SO32-) at acidic to mildly alkaline pH, whereas almost none of the C is present as carbonate anion. Model calculations show that small quantities of SO2 in an early CO2-rich martian atmosphere suppressed formation of carbonates because SO2 is much more water soluble than CO2 and a stronger acid, which may be a major reason why sulfates are much more common than carbonates on Mars. Also, perhaps equally important are low temperatures that favor sulfite mineral precipitation, the oxidation of which leads to sulfate minerals. Another potentially important factor that favors sulfite/sulfide mineral formation is low pH values that cannot allow carbonate minerals, but can allow sulfide minerals such as pyrite (FeS2). The presence of pyrite, highly insoluble, would lead to sulfate minerals when oxygen becomes available in acidic environments. Major cations for both sulfites (or sulfates) and carbonates (Ca and Mg) can limit carbonates. Sulfite-sulfide volcanism on a cold, lower pH, Mars are the primary causes of high sulfate minerals (e.g., Ca and Mg sulfates), compared to volcanism on a warm, higher pH, Earth that led to more abundant carbonate minerals (e.g., Ca and Mg carbonates). © 2013 Elsevier Inc.

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