We study the mineralogy and chemistry of presolar and early solar system materials preserved in cometary dust particles and contemporary comet and interstellar dust that were collected and returned to Earth by the Stardust mission. We use a coordinated analytical approach utilizing transmission electron microscopy (TEM), the ion microprobe, and spectroscopic measurements to extract the maximum science from these primitive materials. We want to learn more about the primordial dusty matter that was the raw material for the formation of the solar system as well as understanding the nature and origin of comets. and will allow direct comparisons to be made with samples of contemporary comet and interstellar dust that were collected and returned to Earth by the Stardust mission.
Our second major research area involves studies of lunar surface materials and focuses primarily on unraveling the complexities of space weathering effects preserved on rock surfaces (patina) and individual soil grains through nm-scale chemical mapping and microstructural studies using TEM. The objective of the proposed research is to determine the petrographic characteristics of individual mineral and glassy grains and surface coatings (patina) that give rise to the modified optical properties measured by remote-sensing. The study of space weathering effects in lunar soils and rocks is directly relevant to understanding the origin and evolution of the lunar regolith as well as the interpretation of global datasets obtained by remote-sensing.
Nakamura-Messenger, K., S. Messenger, L. P. Keller, S. J. Clemett and M. E. Zolensky (2006) Organic globules in the Tagish Lake meteorite: Remnants of the protosolar disk. Science 314, 1439-1442.
Keller, L. P. et al. (2006) Infrared spectroscopy of Comet 81P/Wild 2 samples returned by Stardust. Science, 314, 1728-1731.
Nakamura-Messenger K., Keller L. P., Clemett S. J., Messenger, S., Jones J. H., Palma R. L., Pepin R. O., Klock W., Zolensky M. E. and Tatzuoka, H. (2010) Brownleeite: A new manganese silicide mineral in an interplanetary dust particle. American Mineralogist, 95, 221-228.
Noble, S. K., L. P. Keller and C. M. Pieters (2010) Evidence of space weathering in regolith breccias II: Asteroidal regolith breccias, Meteoritics and Planetary Science, in press.
Keller, L. P. and Messenger, S. (2010) On the origin of GEMS. Geochimica et Cosmochimica Acta, submitted.
Christoffersen, R. and Keller, L. P. (2010) Space radiation processing of sulfides and silicates in primitive solar systems materials: Insights from in-situ TEM ion irradiation experiments. Meteoritics and Planetary Science, submitted.