215 research outputs found
Data for: Raman and reflectance spectroscopy of serpentinites and related hydrated silicates: Effects of physical properties and observational parameters, and implications for detection and characterization on Mars
No full textRaman and reflectance spectra of samples included in this pape
Space Weathering of Airless Bodies
No full textIn preparation for missions to primitive asteroids and to better interpret recent remote sensing datasets from Mercury, the Moon, and other objects, we need a better understanding of how the space environment alters the surfaces of airless bodies from a remote sensing perspective, how analysis of returned samples provides ground truth for interpreting the spectral data, and how laboratory experiments provide quantitative constraints on the processes involved.Organizer Universities Space Research Association ; Conveners Lindsay Keller, NASA Johnson Space Center, Ed Cloutis, University of Winnipeg, Paul Lucey, University of Hawaii, Tim Glotch, Stony Brook University ; Scientific Organizing Committee Lindsay Keller, NASA Johnson Space Center [and 9 others]PARTIAL CONTENTS: The Many Forms of Space Weathering -- Latitudinal Variation in Spectral Properties of the Lunar Maria and Implications for Space Weathering -- Latitude-Dependence of Median Grain Size in the Lunar Regolith -- Space Weathering Effects in the Thermal Infrared: Lessons from LRO Diviner -- Effects of Space Weathering on Thermal Infrared Emissivity Spectra of Bulk Lunar Soils Measured Under Simulated Lunar Conditions -- The Maturely, Immature Orientale Impact Basin -- Estimating the Degree of Space Weathering at the Chang'E-3 Landing Site: Radiative-Transfer Modeling of Nanophase Iron Abundance -- The Microstructure of a Micrometeorite Impact into Lunar Olivine--Simulation of Micrometeorite Impacts Through In Situ Dynamic Heating of Lunar Soil--Problems at the Leading Edge of Space Weathering as Revealed by TEM Combined with Surface Science Techniques--Rates of Space Weathering in Lunar Soils--Space Weathering: From Itokawa to Mercury via the Moon--Space Weathering on Itokawa Surface Deduced from Shape and Surface Features of Hayabusa Regolith Particles--Surface Exposure Ages of Space-Weathered Grains from Asteroid 25143 Itokawa
Geochemical, mineralogical and morphological analysis by spectroscopy of gossan from Axel Heiberg Island, Nunavut, Canada, as Martian analogues
No full textLes chapeaux de fer de l’Arctique sont de bons analogues aux anciens systèmes hydrothermaux sur Mars puisque leur formation est initiée par des processus hydrologiques similaires. La présence de chapeau de fer sur Mars a été suggérée et s’il y en avait, ils représenteraient des cibles prometteuses pour la recherche de traces de vie passée. Ce projet visait à documenter la géochimie, la minéralogie, la morphologie et à faire la détection de carbone organique dans les chapeaux de fer arctiques à l’aide d’une variété d’instruments de spectroscopie pouvant être installés sur des astromobiles. Les analyses géochimiques ont révélé la prédominance du silicium, du calcium et du fer. La minéralogie des échantillons est dominée par le gypse ou le quartz, avec des quantités variables de silicates, de plagioclases, de sulfates, de pyrite et de goethite. Il existe une relation entre la minéralogie et la stratigraphie, les oxydes de fer se trouvant en surface et les sulfures de fer en profondeur. Du carbone organique a été détecté dans la plupart des échantillons. Une origine biologique est supposée, bien qu’aucune autre analyse n’ait été effectuée. La diffraction des rayons X a permis d’identifier plusieurs phases et était la seule technique capable de détecter les sulfures de fer, bien qu’elle ait été moins efficace pour détecter les oxyhydroxydes de fer. La combinaison de la réflectance visible proche-infrarouge, de la réflectance infrarouge moyen-thermique et de la spectroscopie de Raman nous a permis de déduire une minéralogie similaire à ce qui a été détecté par la diffraction des rayons X. Tous les sites étudiés ont été classés comme des chapeaux de fer réactifs, soit en interaction avec le pergélisol. Nous avons observé des profils de chapeau de fer classiques sur tous les sites, où la zone d’altération recouvre la zone de sulfure primaire, mais avec une variété de schémas de stratification. Les variations de composition et de morphologie intra et inter chapeaux de fer soulignent que des mécanismes locaux régulent la distribution spatiale des minéraux et des biosignatures associées. Des recherches supplémentaires visant à mieux comprendre ces variations locales permettraient de guider la recherche de biosignatures dans les chapeaux de fer sur Mars.Abstract : Arctic gossans are good analogs for ancient hydrothermal systems on Mars because their
formation is initiated by similar hydrological processes. They have been hypothesized to be
present on Mars and if they were, they would be of astrobiological interest. The aim of this
project was to document the geochemistry, mineralogy, morphology of Arctic gossans, and
to detect organic carbon in them using a variety of rover-mountable spectroscopic
instruments. Geochemical analyses revealed the predominance of silicon, calcium and iron.
The mineralogy of the samples is dominated by gypsum or quartz, with variable amounts of
silicates, plagioclase, sulfates, pyrite and goethite. There is a relationship between
mineralogy and stratigraphy, with iron oxides being present on the surface and iron sulfides
at depth. Organic carbon was detected in most samples, hypothesized to be of biological
origin, although no further analysis has been carried out. X-ray diffraction identified several
phases and was the only technique capable of detecting iron sulfides, although it struggled
with iron oxyhydroxides. The combination of visible-near infrared reflectance, mid-thermal
infrared reflectance and Raman spectroscopy enabled us to infer similar mineralogical results
to those with X-ray diffraction. All the sites studied were classified as reactive gossans,
interacting with permafrost. We observed classic gossan profiles at all sites, where the
weathering zone overlies the primary sulfide zone, but with a variety of stratification patterns.
Variations in composition and morphology within and between gossans highlight that local
mechanisms regulate the spatial distribution of minerals and associated biosignatures.
Further research to better understand these local variations would help guide the search for biosignatures in gossans on Mars
Olivine-rich exposures in Bellicia and Arruntia craters on Vesta using Dawn FC
No full textThe Dawn Framing Camera (FC) [1] has imaged the entire visible surface of Vesta from three different orbits at spatial resolutions of ~250 m/pixel, ~60 m/pixel, and ~20 m/pixel. The FC is equipped with one clear and seven color filters, cover-ing the wavelength range between 0.44 and 1.0 µm [1]. Vesta is geologically the most diverse differentiated basaltic asteroid that survived the collisional history of the Solar System [2]. Most of the howardite-eucrite-diogenite meteorites (HEDs) and the Vestoids are be-lieved to be samples from Vesta [3], [4]. Several mod-els, based on the petrogenesis of HEDs [5], [6], favor the evolution of Vesta through a magma ocean. How-ever, the variance of incompatible trace elements among diogenites also supports the serial magmatism model [7], [8]. The recent finding of olivine-rich expo-sures in Bellicia and Arruntia craters in the Northern Hemisphere [9], led to many ambiguities, as well as complexities in understanding the geological evolution of Vesta. Here we present our analyses and observa-tions of two olivine-rich exposures. Spectra of HEDs, olivine-orthopyroxene mixtures, olivines, and high Ca-pyroxenes (HCPs) were acquired from RELAB, HOSERLab and USGS. The olivine diagnostic FC parameters we have developed are: Band Tilt (BT) = (R 0.92µm / R 0.96µm) Mid Ratio (MR) = (R 0.75µm / R 0.83µm) / (R 0.83µm / R 0.92µm) Mid Curvature (MC) = (R 0.75µm + R 0.92µm) / R 0.83µm where R(λ) is the reflectance in the corresponding filter
Distribution of Potential Olivine Sites on the Surface of Vesta by Dawn FC
No full textWe report about the most recent results of our olivine mapping of the vestan surface based on Dawn Framing Camera Data
Surface compositional heterogeneity of (4) Vesta from Dawn FC using a 3-dimensional spectral approach
No full textThe historic journey of the Dawn spacecraft in 2011-2012 was a turning point in understanding asteroid (4) Vesta. The surface composition and lithology were analysed and mapped in earlier studies using Dawn imageries [1], [2]. We introduce here a 3-dimensional spectral approach to analyze and map the surface composition using Dawn Framing Camera (FC) color data. Various laboratory spectra of available HEDs and their mixtures, including new spectra measured in this work, were used. Band parameters were reviewed and modified wherever necessary to make the best use of the data. We particularly focused on carbonaceous-chondrite-bearing and olivine-bearing lithologies. An attempt has been made to distinguish glass/impact-melt lithologies
Vesta's diverse lithologies from Dawn FC
No full textWe present the results of an extensive mapping effort of the Vestan surface by using Dawn Framing Camera (FC) data. The identified lithologies are of HED, carbonaceous chondritic and peridotitic nature and include specific sites as, for example, the Marcia crater
Pyroxene reflectance spectra: Minor absorption bands and effects of elemental substitutions
No full textReflectance spectra of a suite of compositionally diverse pyroxenes exhibit variable spectral properties which are associated with various elemental substitutions. Those associated with transition series elements, such as Cr, Ti, V, and Mn, give rise to a number of minor absorption bands in the visible spectral region and, in some cases (e.g., Mn), at longer wavelengths. Substitutions by other cations, such as Li and Zr, do not result in distinct absorption bands. The spectra of these pyroxenes are dominated by the transition series elements that may be present in the samples. The visible wavelength region of low-calcium pyroxene reflectance spectra exhibit a number of absorption bands which are attributable to Fe2+ spin-forbidden crystal field transitions. Fe2+-Fe3+ intervalence charge transfer absorption bands near 0.77 μm are common in terrestrial pyroxenes which contain both ferrous and ferric iron. Collectively, these results indicate that the presence of various transition series elements can be detected in reflectance spectra and that their oxidation states and site occupancies can also be determined on the basis of unique
spectral characteristics present in their reflectance spectra, thereby greatly increasing the range of compositional information which can be derived from analysis of their reflectance spectra.This study was supported by grants-in-aid of research from the Natural Sciences and Engineering Research Council of Canada (NSERC), Sigma Xi, The Scientific Research Society, the Geological Society of America, a research contract from the Canadian Space Agency, and a start-up grant from the University of Winnipeg.https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2001JE00159
Manganese-rich olivines: Identification from spectral reflectance properties
No full textReflectance spectra of manganese-rich olivines were examined to determine which spectral features allow these minerals to be distinguished from forsteritic-fayalitic olivines. The results indicate that manganese-rich olivines can be distinguished on the following bases: Fe2+ M2 absorption band depths are reduced relative to Fe2+ Ml depths, the wavelength position of the Fe2+M2 absorption band is shifted to longer wavelengths(>1.08 μm) for olivines containing between ~10 and 70 mol % Mn2Si04 , and the presence of an isolated Mn2+ transition band near 0.4 μm . The absence of Fe2+ spin forbidden features in the visible wavelength region is not a reliable method for identifying manganese-rich olivines.This work was supported by grants-in-aid of research from the Geological Society of America and Sigma Xi, The Scientific Research Society.This work was supported by grants-in-aid of research from the Geological Society of America and Sigma Xi,
The Scientific Research Societyhttps://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/97JE0249
Olivine-rich exposures in Bellicia and Arruntia craters on Vesta using Dawn FC
No full textThe Dawn Framing Camera (FC) [1] has imaged the entire visible surface of Vesta from three different orbits at spatial resolutions of ~250 m/pixel, ~60 m/pixel, and ~20 m/pixel. The FC is equipped with one clear and seven color filters, cover-ing the wavelength range between 0.44 and 1.0 µm [1]. Vesta is geologically the most diverse differentiated basaltic asteroid that survived the collisional history of the Solar System [2]. Most of the howardite-eucrite-diogenite meteorites (HEDs) and the Vestoids are be-lieved to be samples from Vesta [3], [4]. Several mod-els, based on the petrogenesis of HEDs [5], [6], favor the evolution of Vesta through a magma ocean. How-ever, the variance of incompatible trace elements among diogenites also supports the serial magmatism model [7], [8]. The recent finding of olivine-rich expo-sures in Bellicia and Arruntia craters in the Northern Hemisphere [9], led to many ambiguities, as well as complexities in understanding the geological evolution of Vesta. Here we present our analyses and observa-tions of two olivine-rich exposures. Spectra of HEDs, olivine-orthopyroxene mixtures, olivines, and high Ca-pyroxenes (HCPs) were acquired from RELAB, HOSERLab and USGS. The olivine diagnostic FC parameters we have developed are: Band Tilt (BT) = (R 0.92µm / R 0.96µm) Mid Ratio (MR) = (R 0.75µm / R 0.83µm) / (R 0.83µm / R 0.92µm) Mid Curvature (MC) = (R 0.75µm + R 0.92µm) / R 0.83µm where R(λ) is the reflectance in the corresponding filter
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