Astronomy:Troctolite 76535
Troctolite 76535 is a lunar sample discovered and collected on the Apollo 17 mission in 1972 in the Taurus–Littrow valley. It has a mass of about 156 grams (5.5 oz) and is about 5 centimeters (2.0 in) across at its widest point. It was collected by geologist astronaut Harrison Schmitt as part of a "rake sample" of lunar soil at Geology Station 6, near the base of the North Massif.[1] Troctolite 76535 has been called the most interesting sample returned from the Moon.[2]
Description
Troctolite 76535 is a coarse-grained plutonic rock that is believed to have had a slow cooling history. The rock originates from early in the Moon's history. Geologists have described it as a coarse-grained olivine-plagioclase cumulate with a granular polygonal texture.[2] Olivine and plagioclase are of about equal quantities within 76535, while the remaining approximately 4% is made up of primarily orthopyroxene. According to early studies, the sample cooled at a depth of about 10–20 kilometers (6.2–12.4 mi), as well as its reequilibration and annealing.[3] Later work indicated that the rock formed at a depth of 47 kilometers,[4] about the middle to lower crust of the Moon,[5] Investigations have shown that the rock may have formed as a cumulate at depth, thus possibly making the sample an important link in the understanding of the geologic timeline of the Moon.[6]
As Troctolite 76535 is the oldest known unshocked lunar rock, it has been used for thermochronological calculations in order to determine whether the Moon formed a metallic core or generated a core dynamo. The results of these studies have been shown to support the core dynamo hypothesis.[7]
References
- ↑ "Lunar Sample 76535". Lunar and Planetary Institute, Lunar Sample Atlas. http://www.lpi.usra.edu/lunar/samples/atlas/detail/?mission=Apollo%2017&sample=76535. Retrieved 14 November 2014.
- ↑ 2.0 2.1 "76535 Troctolite". National Aeronautics and Space Administration. http://curator.jsc.nasa.gov/lunar/lsc/76535.pdf. Retrieved 26 October 2010.
- ↑ Ahrens, L. H. (1980). Chemistry of the moon. ISBN 978-0-08-020287-7. https://books.google.com/books?id=lLIfAQAAIAAJ&q=Troctolite+76535.
- ↑ Schwartz, J. M.; McCallum, I. S. (1999). "Inferred Depths of Formation of Spinel Cataclasites and Troctolitic Granulite, 76535 Using New Thermodynamic Data for Cr-Spinel". Lunar and Planetary Science Conference: 1308. Bibcode: 1999LPI....30.1308S.
- ↑ Domeneghetti, M.C. (2001). "Complex Cooling Histories of Lunar Troctolite 76535 and Stillwater Orthopyroxenite SC-936". Lunar and Planetary Science XXXII (2001). http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1151.pdf. Retrieved 24 November 2010.
- ↑ Bogard, D. D. (May 1975). "76535: An old lunar rock". Earth and Planetary Science Letters 26 (1): 69–80. doi:10.1016/0012-821X(75)90178-8. Bibcode: 1975E&PSL..26...69B.
- ↑ Garrick-Bethell, Ian (January 2009). "Early Lunar Magnetism". Science 323 (5912): 356–359. doi:10.1126/science.1166804. PMID 19150839. Bibcode: 2009Sci...323..356G.
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