Radioactive Elements on Mercury's Surface from MESSENGER: Implications for the Planet's Formation and Evolution

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 moder...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2011-09, Vol.333 (6051), p.1850-1852
Main Authors: Peplowski, Patrick N., Evans, Larry G., Hauck, Steven A., 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., Nittler, Larry R., Solomon, Sean C., Rhodes, Edgar A., Sprague, Ann L., Starr, Richard D., Stockstill-Cahill, Karen R.
Format: Article
Language:English
Subjects:
Astronomy
Bombardment
Chemical elements
Earth
Earth, ocean, space
Evolution
Exact sciences and technology
Gamma ray spectrometers
Gamma rays
Materials
Mercury
Mercury surface
Meteorites
Modeling
Planetary composition
Planetary, asteroid, and satellite characteristics and properties
Planetology
Planets, their satellites and rings. Asteroids
Precursors
Radioactivity
Radioisotopes
Silicates
Solar system
Surface features, cratering, and topography
Terrestrial planets
Thermogenesis
Uranium
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Summary: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.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1211576