Publication Date:
2011-10-01
Description:
The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of the radioactive elements potassium (K, 1150 +/- 220 parts per million), thorium (Th, 220 +/- 60 parts per billion), and uranium (U, 90 +/- 20 parts per billion) in Mercury's northern hemisphere. The abundance of the moderately volatile element K, relative to Th and U, is inconsistent with physical models for the formation of Mercury requiring extreme heating of the planet or its precursor materials, and supports formation from volatile-containing material comparable to chondritic meteorites. Abundances of K, Th, and U indicate that internal heat production has declined substantially since Mercury's formation, consistent with widespread volcanism shortly after the end of late heavy bombardment 3.8 billion years ago and limited, isolated volcanic activity since.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Peplowski, Patrick N -- Evans, Larry G -- Hauck, Steven A 2nd -- McCoy, Timothy J -- Boynton, William V -- Gillis-Davis, Jeffery J -- Ebel, Denton S -- Goldsten, John O -- Hamara, David K -- Lawrence, David J -- McNutt, Ralph L Jr -- Nittler, Larry R -- Solomon, Sean C -- Rhodes, Edgar A -- Sprague, Ann L -- Starr, Richard D -- Stockstill-Cahill, Karen R -- New York, N.Y. -- Science. 2011 Sep 30;333(6051):1850-2. doi: 10.1126/science.1211576.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. patrick.peplowski@jhuapl.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21960624" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
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Chemistry and Pharmacology
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Computer Science
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Medicine
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Natural Sciences in General
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Physics
