Ralph E. Milliken Assistant Professor
2007 - 2010 Research Scientist, NASA Jet Propulsion Lab/Caltech
2006 - 2007 Postdoctoral Scholar, Caltech/Jet Propulsion Lab
2006 Ph.D. Geological Sciences, Brown University
2003 M.Sc. Geological Sciences, Brown University
2001 B.S. Geological Sciences, Indiana University
Role of Water in the Formation and Evolution of our Solar System
Spectroscopic Techniques for Characterizing Natural Materials
Formation and Stability of Hydrous Minerals
The Stratigraphic Record of Ancient Mars
Our research group is focused on understanding the geologic evolution of bodies in our solar system by using a combination of laboratory, theory, and remote sensing techniques. This work integrates field and laboratory studies of natural surfaces and minerals to improve interpretations and guide the analysis of remotely acquired data of other planets, moons and asteroids. A major focus is the use of visible-near infrared reflectance spectroscopy for geologic mapping and quantitative determination of mineral abundances on planetary surfaces. The resulting mineralogy can then be integrated with digital topography to measure strike and dip of beds and construct true geologic cross-sections at an unprecedented spatial scale. We are currently collaborating with instrument teams on several spacecraft, including NASA's CRISM spectrometer and HiRISE camera on the Mars Reconnaissance Orbiter and the OMEGA spectrometer on the European Space Agency's Mars Express mission. In addition, we are currently analyzing data to help evaluate potential landing sites for NASA's Mars Science Laboratory rover, scheduled to launch in 2011.
Specific research projects include the study of hydrous minerals such as zeolites, clays, and sulfates, all of which have recently been identified in the ancient stratigraphic record of Mars. Unlike Earth, the ~4.5 -billion-year history of Mars' geologic evolution has been preserved in the rocks at the surface, and this provides a unique opportunity to study the long-term stability of these minerals over timescales not accessible in the terrestrial rock record. In addition, we have recently begun studying interbedded sulfate-carbonate rocks in the Seven Rivers Formation in the Guadalupe Mountains of New Mexico and west Texas using airborne hyperspectral AVIRIS data. Our goal is to combine field, lab, and AVIRIS data to evaluate reflectance spectroscopy as a tool for quantitative mapping of evaporite and clay assemblages, and in turn to determine if such data can be used to identify transitions in depositional environments (e.g., back reef to reef to basin environments) using remotely acquired data.
Other projects include laboratory and theoretical studies to determine the uncertainties and define the limitations of using reflectance spectra to derive mineral abundances of particulate mixtures and rocks, with an emphasis on alteration minerals and the effects of porosity, texture, and particle size. We are currently studying howardite, eucrite, and diogenite meteorites in this context to prepare for interpretation of data returned by NASA's DAWN mission, which will travel to the asteroid 4 Vesta, the purported parent body of these meteorites. The DAWN mission will also travel to the dwarf planet 1 Ceres, and we are continuing to refine techniques for creating quantitative maps of the water content of this body as well as the moon and Mars. Together, these studies work toward our goals of understanding the role of water in the formation and evolution of the solar system and the causes of divergent paths in the geologic and climatic evolution of the terrestrial planets.
Rivkin, A. S., J.-Y. Ling, R. E. Milliken, L. F. Lim, A. J. Lovell, B. E. Schmidt, L. A. McFadden, and B. A. Cohen (2010), The surface composition of Ceres, Space Science Reviews, in press.
Milliken, R. E. and D. Bish (2010), Sources and sinks of clay minerals on Mars, Philosophical Magazine, 90(17), 2293-2308.
Hurowitz, J. A., W. W. Fischer, N. Tosca, and R. E. Milliken (2010), Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars, Nature Geoscience, 3(5), 323-326.
Milliken, R. E., K. Edgett, J. Grotzinger, and B. J. Thomson (2010), Paleoclimate of Mars as captured by the stratigraphic record in Gale Crater, Geophysical Research Letters, 37, L04201.
Sunshine, J., T. Farnham, L. Feaga, O. Groussin, F. Merlin, R. E. Milliken, and M. A'Hearn, (2009), Temporal and spatial variability of lunar hydration as observed by the Deep Impact spacecraft, Science, 326, 565-568.
Metz, J., J. Grotzinger, D. Mohrig, R. E. Milliken et al. (2009), Sublacustrine depositional fans in southwest Melas Chasma, JGR, 114, E10002.
Milliken, R. E., W. Fisher, and J. Hurowitz (2009), Missing salts on early Mars, Geophysical Research Letters, 36, L11202.
Schon, S., J. Head III, R. E. Milliken (2009), A recent ice age on Mars: Evidence for climate oscillations from regional layering in mid-latitude mantling deposits, GRL, 36, L15202.
Milliken, R. E. and A. Rivkin (2009), Brucite and carbonate assemblages from altered olivine-rich materials on Ceres, Nature Geoscience, 2, 258-261, doi:10.1038/NGEO478.
Milliken, R. E., G. Swayze, R. Arvidson, J. Bishop, R. Clark, B. Ehlmann, R. Green, J. Grotzinger, R. Morris, S. Murchie, J. Mustard, and C. Weitz (2008), Opaline silica in young deposits on Mars, Geology, 36(11), 847-850, doi: 10.1130/G24967A.1.
Phone: 574-631-7409
Email: Ralph.Milliken.9(at)nd.edu
Spectroscopy & Remote Sensing
Orbital Remote Sensing of our Environment