Mathematics – Logic
Scientific paper
Sep 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002phdt.........1z&link_type=abstract
PhD Thesis, Rensselaer Polytechnic Institute
Mathematics
Logic
2
Lunar Impact Glasses, Geochemistry, Apollo, Clementine
Scientific paper
NASA defines astrobiology as the study of life in the Universe, its origin, evolution, and distribution, including the role of physical forces, planetary atmospheres, and ecosystem interactions in the evolution of living systems. Such is the scope of the multidisciplinary Origin of Life program at the New York Center for the Studies of the Origin of Life. One of the goals of the center is to determine the impact history of the Earth-Moon system and to evaluate its relevance to the emergence of life on Earth. This thesis focuses on understanding the chemical compositions of lunar impact glasses, which possess the unmodified refractory element ratios of the original fused target materials at the sites of impacts. Working hypotheses are developed that will test the current models for the impact history of the Moon and hence, the Earth, and preliminary evidence provides a key to understanding the pre-Imbrium history of the Moon.
Almost 2400 glasses in regolith samples from the Apollo 14, 16 and 17 landing sites have been analyzed by electron microprobe and are evaluated in this study. These glasses show significant variation and hint at the existence of multiple terrains of differing compositions near each landing site. Clementine color image data have been used to construct iron and titanium maps from which petrologic maps for each Apollo site were created. Comparisons between the Clementine data and the sample data are then made, and the effectiveness of using Clementine image data to place lunar sample information into a regional, and perhaps global, context is demonstrated. Lunar impact glasses and orbital data can thus provide geochemical constraints on the local and regional geology of the Moon.
Analysis of lunar orbital and sample data has lead to the following conclusions:
(1) Anorthositic terrain has been covered by a compositionally-unique KREEP-rich ejecta blanket at each Apollo landing site.
(2) Lunar impact glasses with highland basalt (anorthositic) compositions have been found at each Apollo landing site and may possess a memory of impacts older than 3.9 Ga, contrary to current views.
(3) Compositions of impact glasses, together with an understanding of lunar orbiter data, yield geological information about each landing site and provide constraints on the arrival of components to a surface.
Future work will require determination of ages for the lunar impact glasses found in the regolith using 40Ar/39Ar (argon) radioactive decay dating techniques. These results will better define the bombardment chronology of the Moon (and the Earth) during the first 600 Ma of Solar System history. By knowing the ages of the glasses, the history of bombardment of the early Solar System will be better understood and the timeframe for when life first originated and became sustainable (and continuous) on Earth can be constrained.
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