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|Senior Research Scientist
Planetary Science Institute
I currently have three primary research interests: (1) sedimentary deposits on Mars; (2) soils and small rocks observed at the MER Opportunity rover landing site; and (3) pyroclastic deposits on the Moon. I am a member of the science teams on the MER and MRO (HiRISE) missions. I live in Arlington, VA and work from my home office.
Sedimentary Deposits on Mars
Thick, laterally extensive sedimentary sequences deposited on Mars provide insight into the environmental conditions that prevailed when the sediments were emplaced, while hydrated minerals hold numerous clues to understanding the long history of aqueous activity on the planet. Recent and ongoing studies have placed important constraints on aqueous processes responsible for deposition of sediments in lacustrine systems or that have altered rocks by groundwater or surface flow. By identifying distinct mineral phases and determining how these minerals are associated spatially and temporally, it should be possible to decipher the changing nature of aqueous processes through time. In particular, Valles Marineris contains some of the largest exposures of sedimentary deposits and, consequently, may provide a critical piece of the puzzle to understanding the aqueous and sedimentary history of Mars.
My research uses multiple imagery data sets to map out the 3-dimensional distribution of sedimentary units and look at details that could provide information concerning their origin and relative ages. In particular, I utilize CRISM hyperspectral data and HiRISE high-resolution images of deposits on Mars in order to constrain their mineralogy and morphology, which in term provide insight into how these deposits formed. Right now, I have funding to study these deposits in Valles Marineris and Ladon Basin.
Soils and small rocks at the Opportunity landing site
I have analyzed Microscopic Imager (MI) and Panoramic Camera (Pancam) images from the Opportunity rover at Meridiani Planum on Mars in order to make measurements of grain sizes and spectral properties for soil and small rock particles. The grain-size analyses of the soils at Meridiani Planum have been used to identify rock souces for the grains and provide information about depositional processes under past and current conditions. The Pancam spectral analyses have shown that there are several types of cobbles at the site, including meteorites.
Pyroclastic deposits on the Moon
Pyroclastic glasses on the Moon have been identified remotely from telescopic and orbital data sets, as well as in Apollo samples. They provide important clues concerning the lunar volcanic history of the Moon, especially the history of volatiles within the lunar interior. Important questions remain about their timing in relation to effusive mare basalts, their distribution relative to impact basins, and their importance in terms of potential resources for future manned missions to the Moon. Lunar dark mantle deposits (DMDs) were produced in explosive volcanic eruptions and are identified based upon their relatively low albedos, surface smoothness, mantling relationship to underlying terrain, and spectral absorption bands due to the presence of iron-bearing volcanic glasses. DMDs may be composed of glasses and/or crystallized beads, depending upon the optical density (concentration of gas and clasts for a given volume) of the plume and time within the plume.
I am currently analyzing high spatial and spectral resolution images taken at multiple illuminations to better refine the extent of DMDs, assess whether the medium and smaller size deposits are pyroclastic material or mare ponds, identify and characterize plausible source vents, explore the geologic setting of each deposit, and characterize the eruption that emplaced the deposit. A systematic study across all DMDs has the potential to reveal more about the processes that formed them and the implications of those processes for lunar volcanism and lunar volatiles than the study of one or a few DMDs. The attempt to either group or ungroup DMDs based on new data, and the related task of looking for candidate vents in proximity to the DMDs, could refine the number, type and distribution of DMDs. Additionally, these studies will contribute to lunar resource evaluation, a lunar volatile inventory, and potentially an eventual manned lunar base site selection.