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Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 8, 2013
Rare gas record in the largest apollo 15 rock
Science (New York, N.Y.)
|January 28, 1972
Summary
Cosmic ray exposure data from rock chip 15555,23 reveals a well-shielded location. The calculated krypton-krypton exposure age is 81 million years, with no evidence of plutonium-244 or iodine-129.
Area of Science:
- Geochemistry and Cosmochemistry
- Nuclear Geophysics
Background:
- Understanding rock exposure history is crucial for geological and extraterrestrial studies.
- Cosmic ray interactions provide a method for dating geological samples.
Purpose of the Study:
- To determine the cosmic ray exposure age and shielding history of rock chip 15555,23.
- To search for evidence of specific radioisotopes (plutonium-244, iodine-129) within the sample.
Main Methods:
- Analysis of spallation krypton isotopes within the rock sample.
- Krypton-krypton isochron dating technique.
- Radiochemical analysis for specific fission products.
Main Results:
- Spallation krypton data indicate the rock was well-shielded during most of its cosmic ray exposure.
- A krypton-krypton exposure age of 81(+17)(-7) million years was calculated.
- Gas retention ages were estimated, and no evidence for plutonium-244 or iodine-129 was detected.
Conclusions:
- The rock chip experienced prolonged shielding from cosmic radiation.
- The calculated exposure age provides a significant geochronological marker.
- The absence of specific radioisotopes suggests certain nucleosynthetic or decay pathways were not dominant or present during the rock's history.
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