| Although I maintain a continuing interest in the petrogenesis of plutonic and metamorphic rocks of the Appalachian orogen, my research is now focused on planetary science. My research group, which presently includes three postdoctoral researchers and six graduate students, is involved in the following NASA-funded projects: |
Meteorites
(Funded by a grant from the NASA Cosmochemistry Program.) |
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- Petrology and geochemistry of Martian meteorites These igneous rocks provide constraints on the crystallization and oxidation state of Martian magmas, planetary differentiation and the composition of the crust and mantle, the planet's volatile inventory and outgassed water, geochemical cycles, and the possibility of ancient extraterrestrial life. Our present research utilizes petrography, experiments, and analysis by electron and ion microprobes, as well as collaborative studies with other scientists throughout the world.
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- Petrology and geochemistry of chondritic meteorites: Our studies of chondrites focus on quantifying the conditions of thermal metamorphism in the parent asteroids of ordinary chondrites, describing and understanding aqueous alteration in carbonaceous chondrite asteroids, and characterizing the physical sorting of chondrite components (chondrules and metal grains) in the early solar nebula. We are also studying the least melted chondrules in meteorites to assess their precursor minerals. This research involves petrography, electron probe analysis, and collaborative research using x-ray tomography.
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Asteroid Thermal History and Remote Sensing
(Funded by a grant from the NASA Origins of the Solar System Program.) |
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- Models of asteroid thermal evolution: Computer models of the thermal histories of asteroids heated by short-lived radionuclides are constrained by data from meteorites and asteroids. We have modeled the thermal evolution of 4 Vesta (a large, melted and differentiated body), thermally metamorphosed ordinary chondrite asteroids, and carbonaceous chondrite asteroids that experienced melting of ice and subsequent aqueous alteration. Models under construction now incorporate realistic accretion scenarios for the asteroid belt.
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- Mineralogic constraints on asteroid spectroscopy: Quantifying the mineral abundances and mineral chemistries of meteorites provides a data base for use in interpreting the reflection spectra of asteroids. By documenting progressive changes in mineral proportions during chondrite metamorphism, we have provided an explanation for changes in the rotational spectra of chondritic asteroids. We are also quantifying the mineralogy of unbrecciated eucrites, to be able to model visible/near-infrared spectra to be obtained from the Dawn spacecraft mission. We are employing electron microprobe mapping and other methods for this research.
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Spacecraft Missions
(Funded by a grant through subcontractors for Cornell, Arizona State University, and UCLA, and by a grant from the NASA Data Analysis Program.) |
- Thermal emission spectroscopy for Mars: I'm a member of the TES science team on Mars Global Surveyor and a co-investigator for THEMIS on Mars Odyssey, both now in orbits around Mars. These thermal emission spectrometers provide mineralogic information used in mapping the Martian surface. In addition to being involved in instrument calibration using a variety of terrestrial rocks, we are studying spectral deconvolution using different data sets, the effects of plagioclase zoning on spectra, and the mineralogy of airborne dust.
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- Operations and analysis of data from Mars rovers: As a co-investigator for the Mars Exploration Rovers. I am presently involved in operations, focusing on strategic planning and on integrating and interpreting measurements made by rover instruments of rocks and soils. I have also recently published several papers describing the volcanic rocks found in Gusev crater by the Spirit rover.
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- Asteroid exploration by spacecraft: I am a co-investigator on the Dawn mission, which will orbit and study two of the largest asteroids, Vesta and Ceres. The asteroids are distinct: Vesta is differentiated, and is the parent body for many achondritic meteorites; Ceres is primitive, and may experienced aqueous alteration processes. We have recently determined a new method of interpreting element ratios to be measured by the gamma ray/neutron detector on Dawn, by comparison to HED meteorites thought to be derived from Vesta.
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