Solar flare effects in lunar xenon

Abstract

Low energy solar flare protons induce nuclear reactions in barium isotopes in lunar materials and meteorites with the emission of a few nucleons. Such interactions give rise to the possibility that a compositionally distinct component exists in lunar (also in meteorites) xenon. This component is different from the galactic cosmic ray induced component which in general is produced by the emission of several nucleons. In case of radioactive and stable nuclides, it was shown1-3 that the isotope production by solar cosmic rays in the near surface regions of lunar rocks is limited to the top few millimetres while at greater depths the galactic cosmic rays play the major role. The lunar fines, on the other hand, represent an average of both the galactic and solar cosmic ray effects. Indications of solar flare produced isotopic effects in the light rare gases from Apollo 11, 12 fines have been reported by Yaniv et al. in the Apollo 12 Conference at Houston, 1971, and in case of krypton in Apollo 11 fines by Podosek et al. 4. Here we have analysed in detail the Xe data5,6 obtained in the stepwise heating experiments on soil 10,084 and rocks 10,044 and 10,057 from Apollo 11 with a specific aim of understanding the effects of galactic and solar cosmic rays on lunar surface.