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On the isotopic signature of recent solar-wind nitrogenOne of the most intriguing discoveries yielded by the Apollo samples was evidence pointing towards a significant long-term change in the composition of the sun. Such a change, of the size inferred from the lunar sample data, is inconsistent with present theories of solar evolution. Consequently, there is much interest in exploring this phenomenon as closely as possible, to determine exactly what compositional changes have taken place and whether those changes really did take place in the sun, or whether the cause lies elsewhere. The reason why we can use the moon to analyze the elements in the sun is that the sun emits a stream of ions, known as the solar wind, whose composition, on average, is believed to be the same as that in the surface regions of the sun. When the solar-wind ions hit the surface of the moon, many of them penetrate a short distance into the dust grains lying on the lunar surface. Thus, after a grain has sat on the lunar surface for a while, it has a rim of material that is partly lunar and partly solar in composition. For most chemical elements, the difference between lunar and solar composition is so sufficiently small that the solar elements cannot be detected, but for a handful of elements that are missing from the moon, their solar 'signature' can be observed in samples of lunar soil brought back by the astronauts. Among those elements is nitrogen, the most common element in the air we breathe, but very rare indeed on the moon. Our analytical techniques are not sophisticated enough yet to enable us to analyze individual lunar soil grains for nitrogen, much less to zero in on just the nitrogen in the surface of such a grain. Consequently we are forced to analyze samples consisting of many different grains, each of which could have experienced its own individual history. This makes it difficult to identify the nitrogen implanted in grain surfaces, and also to define the age of a sample.
Document ID
19920021987
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Kim, Y.
(California Univ. San Diego, CA, United States)
Kim, J. S.
(California Univ. San Diego, CA, United States)
Marti, K.
(California Univ. San Diego, CA, United States)
Kerridge, J. F.
(California Univ. San Diego, CA, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1992
Publication Information
Publication: Lunar and Planetary Inst., Twenty-Third Lunar and Planetary Science Conference
Subject Category
Solar Physics
Accession Number
92N31231
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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