The Center for Meteorite Studies is pleased to announce that David Baker, a graduate student at Brown University, has been awarded the 2011 Nininger Meteorite Award.
Matthew Wielicki, a graduate student at the University of California Los Angeles, and Devin Schrader, a graduate student at the University of Arizona, both received an Honorable Mention for the Award.
David’s paper, “The transition from complex craters to multi-ring basins on the Moon: Quantitative geometric properties from Lunar Reconnaissance Orbiter Lunar Orbiter Laser Altimeter (LOLA) data” demonstrates an improved, semi-automated technique to measure the morphometric properties of peak-ring basins (single interior ring of peaks, or “peak ring”) and protobasins (peak ring plus central peak) on the Moon using new topography data from the Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA). Analyses of these morphometric characteristics with crater size revealed new trends that now provide an observational framework for testing models for the formation of peak-ring basins on planetary bodies. Among the trends, David and his coauthors found a discontinuity in depth measurements from complex craters to peak-ring basins and continuous increases in central peak dimensions up to the transition to peak-ring basins. These observations of peak-ring basins on the Moon provide a foundation for understanding the formation of larger multi- ring basins and are already serving as a benchmark for similar morphometric analyses of basins on other planetary bodies such as Mercury. David’s research was conducted under the advisement of Dr. James W. Head.
Devin’s paper, “The Formation and Alteration of the Renazzo-like Carbonaceous Chondrites II: Linking O-isotope Composition and Oxidation State of Chondrule Olivine” discusses the formation conditions of type-I and type-II chondrules in the Renazzo-like carbonaceous (CR) chondrites. Through an in situ major- and minor-element and O-isotope study, Devin and his co-authors infer that type-II chondrule precursors contained enhanced S-bearing dust and ice abundances relative to type-I chondrules, and find a relationship between the O-isotope composition and oxidation state of olivine, which may be related to the amounts of 16O-poor ice and reduced carbon accreted by chondrule precursors before melting. They also find that Type-II chondrules formed under H2O/H2 ratios of ~220–700 times solar, where type-I chondrules formed under more reducing conditions with lower H2O/H2 ratios of ~10–100 times solar. The study finds a relationship between type-II chondrule petrology (relict free vs. relict grain-bearing) and O-isotope composition, which is due to degree of melting and exchange with a 16O-poor gas reservoir. The 16O-poor gas that interacted with both type-I and type-II chondrules is estimated, and found to be different from the O-isotope composition of the water accreted by the CR chondrite parent body. This work suggests that, due to partial melting, type-I chondrules and relict grain-bearing type-II chondrules. Devin’s research was conducted under the advisement of former Nininger Meteorite Award recipient Dr. Dante Lauretta.
Matthew’s paper, “Geochemical Signatures and Magmatic Stability of Terrestrial Impact Produced Zircon” compares terrestrial impactites, ranging in age from ~35 Ma to ~2 Ga, with detrital Hadean zircon from Western Australia. Such comparisons may provide the only terrestrial constraints on the role of impacts during the Hadean and early Archean, a time predicted to have a high bolide flux. Ti-in-zircon thermometry indicates an average of 773°C for impact produced zircon, ~100°C higher than the average for Hadean zircon crystals. The agreement between whole-rock based zircon saturation temperatures for impactites and Ti-in-zircon thermometry implies that Ti-in-zircon thermometry record actual crystallization temperatures for impact melts. Zircon saturation modeling of Archean crustal rock compositions undergoing thermal excursions associated with the Late Heavy Bombardment predict equally high zircon crystallization temperatures. The lack of such thermal signatures in the Hadean zircon record implies that impacts were not a dominant mechanism of producing the preserved Hadean detrital zircon record. Matthew’s research was conducted under the advisement of Dr. Mark Harrison.
Each submission was reviewed by an international panel of experts from a broad array of fields in meteoritical science.