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Apollo 12 ropy glasses revisitedWe analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and Ar-39-Ar-40 age dating. The ropy glasses have potassium rare earth elements phosphorous (KREEP)-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component. Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma. Measurements of 39-Ar-40-Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact. Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly.
Document ID
19950031753
Document Type
Reprint (Version printed in journal)
Authors
Wentworth, S. J. (Lockheed Engineering and Science Co., Houston, TX United States)
Mckay, D. S. (NASA Johnson Space Center Houston, TX, United States)
Lindstrom, D. J. (NASA Johnson Space Center Houston, TX, United States)
Basu, A. (Indiana Univ. Bloomington, IN, United States)
Martinez, R. R. (Lockheed Engineering and Science Co., Houston, TX United States)
Bogard, D. D. (NASA Johnson Space Center Houston, TX, United States)
Garrison, D. H. (Lockheed Engineering and Science Co., Houston, TX United States)
Date Acquired
August 16, 2013
Publication Date
May 1, 1994
Publication Information
Publication: Meteoritics
Volume: 29
Issue: 3
ISSN: 0026-1114
Subject Category
LUNAR AND PLANETARY EXPLORATION
Distribution Limits
Public
Copyright
Other