Although I maintain a continuing interest in the petrogenesis of terrestrial igneous and metamorphic rocks, my research is now focused on planetary science. My research group, which presently includes a postdoctoral researcher and three graduate students, is involved in the following NASA-funded projects:
Petrology and Cosmochemistry of SNC Meteorites
These igneous rocks provide constraints on the mineralogic and geochemical composition and crystallization 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.
Petrology and Geochemistry of HED Meteorites
We are quantifying the mineral abundances and chemical compositions of HED meteorites to understand their effects on visible/near-infrared and gamma-ray/neutron spectra. Our studies focus on how these rocks formed and what they can tell us about differentiated planetesimals. This work utilizes electron and ion probe analyses, as well as trace element analyses by LA-ICP-MS.
Petrology and Cosmochemistry of Chondritic Meteorites
Current and recent studies of chondrites have focused on quantifying the conditions of thermal metamorphism in the parent asteroids of ordinary chondrites, understanding the degree of aqueous alteration in carbonaceous chondrites, and characterizing the physical sorting of chondrite components (chondrules and metal grains) in the early solar nebula. This research involves petrography, electron probe analysis, and collaborative research using x-ray tomography.
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.
Mineralogic and Chemical Constraints on Asteroid Spectroscopy
Quantifying the mineral abundances and mineral chemistries of meteorites provides a database 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 have quantified the mineralogy of eucrites and diogenites, to be able to model visible/near-infrared spectra to be obtained from the Dawn spacecraft mission. Our studies of HED meteorite chemistry are used to calibrate and interpret gamma-ray/neutron spectra from the Dawn GRaND instrument.
Thermal Emission and Gamma-ray Spectroscopy for Mars
I'm a co-investigator for THEMIS and a collaborator for GRS on Mars Odyssey, now in orbit around Mars. These spectrometers provide mineralogic and geochemical information used in mapping the Martian surface. In addition to being involved in instrument calibration using a variety of terrestrial rocks, we have studied spectral deconvolution using different spectral library minerals, the effects of plagioclase zoning on spectra, the spectra and mineralogy of airborne dust, and the petrology of volcanic terrains on Mars.
Operations and Analysis of Data from Mars Rovers
As a co-investigator for the Mars Exploration Rovers. I have been involved in operations, focusing on strategic planning and on integrating and interpreting measurements made by rover instruments of rocks and soils. We have published numerous papers describing the volcanic and sedimentary rocks found in Gusev crater and Meridiani by the Spirit and Opportunity rovers, and as well as the compositions and origin of soils analyzed by the rovers.
Asteroid Exploration by Spacecraft
I am a co-investigator on the Dawn mission, which is studying the two most massive asteroids, Vesta and Ceres. The asteroids are distinct: Vesta is differentiated, and is the parent body for many achondritic meteorites; Ceres is primitive, and likely experienced aqueous alteration processes. We use information from meteorite studies to constrain Dawn remote-sensing data, and coordinate the mineralogical and geochemical analyses performed by the surface composition working group.