In addition to the planetary geology research described above, I am striking out in some new directions as well. For example, along with my colleague Jim Bayman in the Department of Anthropology at the University of Hawaii, I have begun a pilot study investigating the utility of visible to thermal IR spectroscopy as an archaeometric tool for characterizing and sourcing archaeological artifacts made of geomaterials. Another study that I'll be working on with colleague Patty Fryer, also at the University of Hawaii, will examine how we can use infrared spectroscopy to rapidly characterize the composition and orientation of minerals in seafloor rock samples from convergent plate margins (subduction zones). We want to understand the relationship between these characteristics and observed seismic anisotropy.

My curriculum vitae in PDF format.

Martian TES and THEMIS data analysis projects

• Mineralogy of rocks at the Gusev crater landing site: Five years after landing on the surface of Mars, the Mars Exploration Rover Spirit has collected thousands of thermal infrared spectra of rocks and soils. These spectra reveal a diversity of mineralogies, and detailed analysis of these materials can give us insight into the primary and secondary geologic processes that have occurred on Mars. This research is a collaborative effort with Dr. Steve Ruff at Arizona State University.

• Visible, near infrared, and thermal infrared spectroscopy of cherts and amorphous silica: Cherts and amorphous silica can be formed by both biogenic and abiogenic processes, and they exhibit a wide variety of structural characteristics and hydration states that can be indicative of their geologic history. Silica has been identified on Mars in remote and in situ spectroscopic data across the VNIR and TIR wavelength regions, and it is therefore important to understand the full range of spectral characteristics exhibited by these materials as a function of chemical, structural, and physical properties, as well as their environments of formation. In particular, little work has been done to acquire emission spectra, which are essential for interpreting remote sensing (including in situ) data. This research is led by my former graduate student, Dr. Meryl McDowell.

• Thermophysical and topographic characteristics of putative chloride deposits: The recent THEMIS/TES discovery of putative chloride deposits on the Martian surface raises many questions about the origin and history of these spectrally unusual materials. Global characterization of their thermophysical and topographic properties may shed more light on these intriguing deposits and what they may be able to tell us about the past presence of water on Mars.

• Characterizing the diversity of olivine compositions across Mars: Linear least squares modeling and spectral index mapping show that much of the Martian surface is composed of olivine-bearing materials. The compositions of the olivines vary from magnesium-rich (forsteritic) to relatively iron-rich (fayalitic), indicating differences in the source magmas from which they were crystallized. The results of this study were published by Koppen and Hamilton in the May 2008 issue of the Journal of Geophysical Research.

• Searching for the source regions of Martian meteorites (SNCs): Systematic analysis of thermal infrared spectra of the Martian surface, using laboratory spectra of the meteorites, has identified Martian meteorite- like materials (olivine- and orthopyroxene-bearing) on the surface of Mars. Understanding the geologic environments of these materials may help us determine if they are potential source regions for the meteorites. Identifying the physical origin of these Martian samples would allow scientists to place these rocks into a geologic context that we currently lack. And could ultimately allow us to assign better absolute ages to portions of the Martian surface. See the results of our global search.

• Spectroscopic analysis of compositional variations within Syrtis Major and environs, Mars: Syrtis Major is a large, dark region on Mars with some of the best exposed, relatively unweathered material on the planet. Recent studies [Bandfield et al., 2000; Hamilton et al., 2003] suggest that this region displays compositional variation in TES data that merit more detailed investigation.

• Examinations of Martian fine materials: Based on the laboratory studies of crushed and powdered rocks mentioned above, I have been able to begin to place additional constraints on the compositions and mean apparent particle size of the dusty surfaces that cover much of Mars. The nature of these materials is still only poorly understood, so it is my hope that these studies will help fill in the gaps in our knowledge.

Laboratory research projects

• Microspectroscopy of meteoritic materials: Meteorites contain a vast array of minerals and other phases that represent a wide variety of geological processes, relevant to the formation and evolution of asteroids and rocky planets. Many of these phases are physically small or are difficult to obtain in significant quantities on Earth, and are best analyzed using microscopic techniques. Acquiring their infrared spectra helps us augment the spectral libraries used to interpret data collected by remote sensing instruments throughout the solar system. This work is joint effort with Dr. Gretchen Benedix of the Natural History Museum in London.

• Spectral characteristics of altered tephras: Palagonite, a weathering product of mafic rocks, has long been proposed as a visible/near infrared spectral analogue of Martian bright regions. The midinfrared properties of this variable material are not well known. Obtaining a spectral library of altered tephras, including palagonite, will help us to determine if this material is also a viable analogue for midinfrared spectra of Martian bright regions as well. This is a joint research effort with Dr. Richard Morris of NASA Johnson Space Center. This work has been published in a 2008 special issue of the Journal of Geophysical Research.

• Visible, near-, and middle infrared spectral investigation of the pyroxene mineral series: Pyroxenes are important minerals in many igneous rocks on Earth and on the Martian surface -- an understanding of their variable spectral characteristics as a function of crystal structure and composition will help us to better determine the chemistries of pyroxenes observed in Martian spectra. Knowledge of these compositions will provide more specific information about the conditions during eruption of pyroxene-bearing rocks on Mars. See an example diopside spectrum.

• Middle infrared spectral characteristics of Martian meteorites (SNCs): Martian meteorites, pieces of Mars on Earth, are an important piece of our understanding of the geology of Mars. Unfortunately, we do not know where on Mars these samples came from. By analyzing their spectral signatures in the laboratory, we can look for similar spectra in the Martian data returned by TES and THEMIS.

• Visible, near-, and middle infrared spectral properties of igneous rocks: Only by studying the spectral characteristics of a wide variety of well- understood terrestrial samples can we truly understand what spectral data from Mars may be telling us.

• Middle infrared spectral studies of particulate rocks: In the world of spectroscopy, the size of the particles being observed can influence the appearance of the spectrum, making it difficult to recognize the mineralogy of the material observed. In some cases, the physics of this process are very difficult to understand, even for pure, single-mineral specimens. However, it is important to know how particle sizes affect the spectral signatures of crushed rocks so that we can recognize these effects in spectra of planetary surfaces (e.g., Mars, asteroids) and use them to our advantage in interpreting the compositions and physical properties of these bodies.

• Spectral characteristics of glasses and phyllosilicates: Some phyllosilicates have spectral characteristics that are broadly similar to those of glasses. The distinction between these phases in remote sensing data has important implications for how remotely acquired spectral data are interpreted. A thorough understanding of how well they can be distinguished is proving critical to the interpretation of data from Mars.

• Quantitative modeling of visible, near-, and middle infrared spectra: Ultimate application of the results of our laboratory studies to the interpretation of remote sensing data requires a quantitative understanding of how well spectral properties can be used to successfully predict mineralogy, chemistry, and other properties of interest. Blind and semi-blind testing of spectral/chemical correlations via numerical models (e.g., linear deconvolution, gaussian modeling) is critical to this effort.

Venusian Tectonics

My interest in Venusian geology started with a NASA internship at the Jet Propulsion Laboratory working with the Magellan science team. Magellan was a synthetic aperture radar (SAR) orbiter that used radar to map the surface of Venus through the thick cloud layer that encircles the planet and prevents visual observations. The images produced by Magellan look a lot like black and white photographs, but they really are images of surface roughness and surface slopes. My main interest is in a class of features called coronae, particularly their occurrence in "chains" along semi-linear tectonically deformed belts. The area I'm primarily interested in is central Hecate Chasma.

There are several sites which provide access to information about the Magellan Mission to Venus and Magellan data, including: the Magellan Data Archives, JPL's Magellan Mission to Venus homepage, and the USGS Astrogeology Branch.

Venus SAR and Topography 442 k