{sup 41}Ca, {sup 26}Al, and {sup 10}Be in lunar basalt 74275 and {sup 10}Be in the double drive tube 74002/74001
- ANSTO, Menai, New South Wales (Australia). Physics Div.
- Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Physics
- Rutgers Univ., New Brunswick, NJ (United States). Dept. of Chemistry
- Los Alamos National Lab., NM (United States)
The authors report depth profiles of the cosmogenic radionuclides {sup 10}Be, {sup 26}Al, and {sup 41}Ca in the titanium-rich lunar basalt 74275. The {sup 10}Be profile is flat: {sup 10}Be activities are confined to a narrow range between 9.6 and 11.2 dpm/kg but are nonetheless consistent with a small contribution of about 1--2 dpm/kg from solar cosmic rays. The {sup 26}Al profile shows the steep decrease with increasing depth that is characteristic of nuclides whose production is dominated by solar cosmic rays. {sup 41}Ca activities decrease from about 22 dpm/kg at the surface to a minimum of {approximately}9 dpm/kg at a depth of 4.7 g/cm{sup 2} and then increase to {approximately}11 dpm/kg at a depth of 15.8 g/cm{sup 2}. The sharp decrease near the surface identifies for the first time production of {sup 41}Ca by solar cosmic rays. The authors also report {sup 10}Be measurements for six samples from lunar core 74002/1. The {sup 10}Be activities range from approximately 8 to 14 dpm/kg. They model the production of {sup 10}Be, {sup 26}Al, and {sup 41}Ca in lunar rock 74275 by including published data that indicate a long exposure to galactic cosmic rays at a depth of 140 g/cm{sup 2} followed by one at the surface lasting 2.8 Ma. Cosmogenic radionuclide production by galactic cosmic rays, and, in the case of {sup 41}Ca, by thermal neutrons is estimated from published measurements and semi-empirical calculations. The model includes a new calculation of production rates due to solar cosmic rays and incorporates recently published cross section measurements.
- Sponsoring Organization:
- National Aeronautics and Space Administration, Washington, DC (United States); USDOE, Washington, DC (United States)
- OSTI ID:
- 655494
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 13 Vol. 62; ISSN GCACAK; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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