Surface reflectance of Mars observed by CRISM/MRO: 2. Estimation of surface photometric properties in Gusev Crater and Meridiani Planum

The present article proposes an approach to analyze the photometric properties of the surface materials from multi-angle observations acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on-board the Mars Reconnaissance Orbiter. We estimate photometric parameters using Hapke model in a Bayesian inversion framework. This work also represents a validation of the atmospheric correction provided by the Multi-angle Approach for Retrieval of Surface Reflectance from CRISM Observations (MARS-ReCO) proposed in the companion article.The latter algorithm retrieves photometric curves of surface materials in reflectance units after removing the aerosol contribution. This validation is done by comparing the estimated photometric parameters to those obtained from in situ measurements by Panoramic Camera instrument at the Mars Exploration Rover (MER)-Spirit and MER-Opportunity landing sites. Consistent photometric parameters with those from in situ measurements are found, demonstrating that MARS-ReCO gives access to accurate surface reflectance. Moreover the assumption of a non-Lambertian surface as included in MARS-ReCO is shown to be significantly more precise to estimate surface photometric properties from space in comparison to methods based on a Lambertian surface assumption. In the future, the presented method will allow us to map from orbit the surface bidirectional reflectance and the related photometric parameters in order to characterize the Martian surface

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

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 π; 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_2 absorption in the H_2O ice bands at wavelengths near 2.0 µm. 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

Orbital Observations of Dust Lofted by Daytime Convective Turbulence

Over the past several decades, orbital observations of lofted dust have revealed the importance of mineral aerosols as a climate forcing mechanism on both Earth and Mars. Increasingly detailed and diverse data sets have provided an ever-improving understanding of dust sources, transport pathways, and sinks on both planets, but the role of dust in modulating atmospheric processes is complex and not always well understood. We present a review of orbital observations of entrained dust on Earth and Mars, particularly that produced by the dust-laden structures produced by daytime convective turbulence called “dust devils”. On Earth, dust devils are thought to contribute only a small fraction of the atmospheric dust budget; accordingly, there are not yet any published accounts of their occurrence from orbit. In contrast, dust devils on Mars are thought to account for several tens of percent of the planet’s atmospheric dust budget; the literature regarding martian dust devils is quite rich. Because terrestrial dust devils may temporarily contribute significantly to local dust loading and lowered air quality, we suggest that martian dust devil studies may inform future studies of convectively-lofted dust on Earth

Caractérisation des propriétés physiques de la surface de Mars à partir de mesures spectro-photométriques orbitales

The PhD work focuses on the characterization of geological processes on planetary surfaces. Due to the lack of broad scale in situ information about the surface physical properties of the Martian materials (recording the geological processes), my work centers on the development and validation of an approach for their estimation from orbital spaceborne datasets. In addition, determining the physical properties has an implication for the spectroscopic interpretation notably for the mineral abundances. More specifically, I developed an approach for the determination and the analysis of the Martian surface scattering properties using CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) observations [Murchie et al., 2007] on-board MRO (Mars Reconnaissance Orbiter). CRISM provides multi-angular (varied emission angles) hyperspectral images which allow the characterization of the surface scattering behavior at ∼200m/pixel. The scattering behavior depends on the material composition but also the physical properties such as the grain size, shape, internal structure, and the surface roughness / porosity. The main objective is to observe the spatial variations of the surface scattering properties and the photometric parameters as a function of geological units.The methodology I employ is based on the estimation of the surface photometric parameters in term of surface physical properties. After an atmospheric correction (aerosols) by the Multi-angle Approach for Retrieval of the Surface Reflectance from CRISM Observations (MARS-ReCO) [Ceamanos et al., 2013] developed in collaboration with X. Ceamanos and S. Douté (IPAG, France), I analyze the surface reflectance taken at varied geometries by inverting the Hapke photometric model [Hapke, 1993] depending on six parameters (single scattering albedo, 2-term phase function, macroscopic roughness and 2-term opposition effects parameters) in a Bayesian framework [Fernando et al., 2013]. The algorithm for the correction for the aerosols and the methodology for the estimates of surface photometric parameters have been validated by comparing the results from orbit to the in situ photometric measurements from Mars Exploration Rover (MER) rovers [Fernando et al. 2013].The MER landing sites located at Gusev Crater and Meridiani Planum provide an excellent opportunity to ground truth and validate the interpretation of derived Hapke photometric parameters as both orbital and in situ data are readily available over numerous geological terrains. Orbital results are consistent with the in situ observations. In my work, I mapped the surface scattering properties in and around the rover path, providing extended information over a wider area. Significant variations in the scattering properties are observed inside a CRISM observation (10x10km) suggesting that the surfaces are controlled by local geological and climatic processes [Fernando et al., in revision].The last part of this work focuses on the determination of the surface photometric parameters of different Martian geological terrains under different contexts in order to identify variabilities of the scattering propertiesDepuis leur formation, les surfaces des corps de notre Système Solaire montrent une diversité étonnante. Cette diversité est le reflet des processus géologiques qui ont modelé les surfaces planétaires au cours du temps. Parmi les objets du Système Solaire, Mars constitue un objet particulièrement intéressant car il présente de nombreuses similitudes avec notre planète. La minéralogie de la surface de Mars est bien documentée. Cependant, on dispose de peu d'information sur les paramètres physiques des matériaux qui sont également des traceurs des processus géologiques. Un des objectifs de cette thèse est de développer et de valider un outil permettant leur détermination à partir de techniques d'investigation spatiale depuis l'orbite et d’interpréter les résultats. Pour cela, une approche basée sur la photométrie, qui étudie les propriétés de diffusion des matériaux de surface, a été développée et validée. Ces propriétés de diffusion dépendent de la composition mais aussi des propriétés physiques des matériaux comme la taille, la forme, la structure interne, la rugosité des grains et la rugosité de la surface. Les données hyperspectrales multi-angulaires CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) à bord de la sonde Mars Reconnaissance Orbiter (11 images prises à des angles d'émergence variés) ont été utilisées, permettant de contraindre le comportement de diffusion des matériaux de surface. Tout d'abord, les données sont corrigées de la contribution atmosphérique à l'aide de l'algorithme nommée MARS-ReCO (Multi-angle Approach for Retrieval of Surface Reflectance for CRISM Observations), développé en collaboration avec Xavier Ceamanos et Sylvain Douté (IPAG) au cours de la thèse. Puis, les données de réflectance de surface à différentes géométries sont analysées en inversant à l’aide d’une approche bayésienne le modèle photométrique de Hapke qui décrit le transfert radiatif en milieu granulaire. Ce modèle dépend de six paramètres photométriques de surface (e.g., albédo de diffusion, fonction de phase, rugosité macroscopique de la surface), reliés aux propriétés physiques des matériaux comme la taille, la structure interne, la forme, la rugosité des grains, et la rugosité de la surface.Une première application a été menée au niveau des sites d'atterrissage des rovers de la mission Mars Exploration Rover, où des données orbitales et in situ sont disponibles. Ces dernières sont utilisées comme «vérité terrain» pour valider les interprétations des paramètres photométriques estimés. Dans ce travail, des cartes des paramètres photométriques ont été fournies le long et autour du trajet des rovers permettant d'avoir accès aux informations des propriétés des matériaux sur une étendue plus importante que les données in situ. Une interprétation de chacun des paramètres et un lien aux propriétés physiques et aux processus géologiques ont été fournis. Les résultats montrent des propriétés de diffusion variés au sein d'une observation CRISM (10x10km) suggérant que les surfaces sont contrôlées par des processus géologiques plus locaux (e.g., processus éoliens, fragmentation de la croûte par impact).Une dernière partie se focalise sur la détermination des propriétés de diffusion des matériaux de surface de différents terrains géologiques formés dans des contextes différents. Le but est d'identifier les variabilités des propriétés de diffusion à travers Mar

Characterization of Martian Surfaces using Mechanical and Spectrophotometric Models

Two recent in situ Mars missions, the Phoenix Mars Lander and the Mars Exploration Rover Opportunity, have explored two quite different locations on the surface of Mars. The Phoenix lander investigated the polygonal terrain and associated soil and icy soil deposits of a high northern latitude site: 68.22° N, 234.25° E). The Opportunity rover, the only currently operational spacecraft on the surface of Mars, is located much closer to the equator: 1.95° S, 354.47° E), and has been exploring the plains and sedimentary rocks in Meridiani Planum. Concurrent with in situ Opportunity and Phoenix observations, the Compact Reconnaissance Imaging Spectrometer for Mars: CRISM) was in orbit around Mars collecting hyperspectral data. In this dissertation, surface and orbital data are used to explore and characterize surface material properties at the Phoenix and Opportunity sites. The Phoenix soil physical properties experiments involved the analysis of forces determined from motor currents from the Robotic Arm: RA)’s trenching activities. Using this information and images of the landing site, soil cohesion and angle of internal friction were determined. Soil dump pile slopes were used to determine the angle of internal friction of loose soil: 38° ± 5°. Additionally, an excavation model that treated walls and edges of the RA’s scoop as retaining walls was used to calculate mean in situ soil cohesion values for several trenches in the Phoenix landing site workspace. These cohesions were found to be consistent with the stability of steep trench slopes. Cohesions varied from 0.20.4−0.2 kPa to 1.21.8−1.2 kPa, with the exception of a subsurface platy horizon unique to a shallow trough for which cohesion will have to be determined using other methods. Soil on a nearby polygon mound had the greatest cohesion: 1.21.8−1.2 kPa). This high cohesion value was most likely due to the presence of adsorbed water or pore ice above the shallow icy soil surface. Further evidence for enhanced soil cohesion above the ice table includes lateral increase in excavation force, by over 30 N, as the RA approached ice. The behavior of soil near the ice table interface is of particular interest considering that many of the high-latitude and mid–latitude regions of Mars are underlain by ice. For the region traversed by Opportunity in the vicinity of Victoria crater, normalized spectral radiances from the Compact Reconnaissance Imaging Spectrometer for Mars: CRISM) were used to retrieve surface scattering properties. Estimates agree with those retrieved in previous photometric studies which used Opportunity–s Panoramic Camera: Pancam) data, and I was able to extend estimates of the Hapke single particle scattering albedo and asymmetry parameter: from the one–term Henyey Greenstein single particle phase function) to a greater spatial and spectral range. Results are useful for determining the boundaries between surface units that otherwise look relatively uniform spectrally. This work also provides photometric functions essential for converting spectra to a single viewing geometry which will yield more accurate spectral comparisons. Results were obtained through simultaneous modeling of surface and atmospheric contributions, iterating through surface scattering parameters until a Levenberg–Marquardt least squares best fit was achieved. Retrieved single scattering albedos range from 0.42 to 0.57: 0.5663 − 2.2715 micrometers), and retrieved asymmetry parameters range from −0.27 to −0.17: moderately backscattering). All surfaces become more backscattering with increasing wavelength. The majority of Victoria crater’s ejecta apron is more backscattering than surrounding regions, indicating a change in physical properties. Images taken when the rover traversed this unit show a cover of basaltic soil with superposed millimeter–scale hematitic spherules, providing agreement with previous analyses of lab experiments showing increased backscattering with the addition of hematitic spherules. Dark wind streaks on the apron appear smooth: low backscatter) because basaltic sands have partly buried spherules, lessening millimeter–scale roughness: in agreement with previous near–surface wind streak analyses). The CRISM–derived scattering parameters also show that bedrock–dominated surfaces are less backscattering than soil–covered surfaces, largely due to lower areal abundance of spherules. The ability to analyze surface unit spherule cover is important because it relates to a wetter period during which spherules formed in Meridiani

Study of martian dust aerosol with mars science laboratory rover engineering cameras.

167 p.Planetary atmospheres other than that of Earth provide natural laboratories to test our theories and models for climate studies and can help to identify the physical processes involved in the behaviour and evolution of a planet's climate. Mars has always played a predominant role in comparative studies with Earth. Extensive efforts placed in the robotic exploration of Mars have retrieved large amount of data its atmosphere. Dust aerosol is the main driver of Mars' atmospheric variability, and the determination of the particles' properties is of high relevance for estimating its climate forcing. In particular, the angular distribution of sky brightness can be evaluated to retrieve valuable information regarding the physical properties of the aerosol particles. In this study we show that images retrieved by the Mars Science Laboratory (MSL) engineering cameras (Navcam and Hazcam) can be used to constrain the size and shape of dust aerosol particles, and to derive the column dust optical depth. A radiative transfer based iterative retrieval method was implemented in order to determine the aerosol modelling parameters that best reproduce the sky radiance as a function of the scattering angle observed by MSL engineering cameras. Results show an overall good agreement with previous studies and have contributed to extend the available data and to parameterise dust phase functions. The tools and procedures developed during this research can be implemented for the analysis of retrievals from future Mars exploration missions

Study of martian dust aerosol with mars science laboratory rover engineering cameras.

167 p.Planetary atmospheres other than that of Earth provide natural laboratories to test our theories and models for climate studies and can help to identify the physical processes involved in the behaviour and evolution of a planet's climate. Mars has always played a predominant role in comparative studies with Earth. Extensive efforts placed in the robotic exploration of Mars have retrieved large amount of data its atmosphere. Dust aerosol is the main driver of Mars' atmospheric variability, and the determination of the particles' properties is of high relevance for estimating its climate forcing. In particular, the angular distribution of sky brightness can be evaluated to retrieve valuable information regarding the physical properties of the aerosol particles. In this study we show that images retrieved by the Mars Science Laboratory (MSL) engineering cameras (Navcam and Hazcam) can be used to constrain the size and shape of dust aerosol particles, and to derive the column dust optical depth. A radiative transfer based iterative retrieval method was implemented in order to determine the aerosol modelling parameters that best reproduce the sky radiance as a function of the scattering angle observed by MSL engineering cameras. Results show an overall good agreement with previous studies and have contributed to extend the available data and to parameterise dust phase functions. The tools and procedures developed during this research can be implemented for the analysis of retrievals from future Mars exploration missions

Solar System Remote Sensing : September 20-21, 2002, Pittsburgh, Pennsylvania

This international meeting presents the current state of research over a wide range of topics including:; Photometric theory; Spectroscopic modeling; Laboratory exploration of scattering phenomena; Space weathering processes throughout the inner solar system; Photometric and spectroscopic studies of the Moon, Mars, Mercury, and asteroids; Photometric and spectroscopic studies of cold, icy places such as comets and outer planet satellites.This international meeting presents the current state of research over a wide range of topics including:; Photometric theory; Spectroscopic modeling; Laboratory exploration of scattering phenomena; Space weathering processes throughout the inner solar system; Photometric and spectroscopic studies of the Moon, Mars, Mercury, and asteroids; Photometric and spectroscopic studies of cold, icy places such as comets and outer planet satellites.sponsors, University of Pittsburgh ... [and others]conveners, William Cassidy, Deborah Domingue, Robert M. Nelson ; scientific organizing committee William Cassidy ... [and others].PARTIAL CONTENTS: Interpreting Photometry of Planetary Regoliths: Progress and Problems as Seen from Kharkov / Yu.G. Shkuratov--Toward an Improved Single-Particle Model for Large, Irregular Grains / W.M. Grundy, B. Schmitt, S. Doute--A New Method for Estimating the Single Scattering Phase Functions of Regolith Grains / P. Helfenstein--The Opposition Effect: A Very Unusual Case / R.M. Nelson--Coherent Backscattering by Random Particulate Media in the Solar System / K. Muinonen--The Diverse Surface Compositions of the Galilean Satellites / R.W. Carlso