K J Mathew
Articles written in Journal of Earth System Science
Volume 102 Issue 3 September 1993 pp 415-437
Production rates of15N by both solar cosmic rays (SCR) and galactic cosmic rays (GCR) have been calculated for moon, as well as meteorites of various sizes. Our production rates of15N which considered both the reaction channels16O(p, pn)15O and16O(p, 2p)15N separately are about 30% higher than those by Reedy (1981) who considered only the channel16O(p, pn)15O and used an empirical scaling factor to estimate the contribution from16O(
Volume 107 Issue 4 December 1998 pp 425-431
We discuss observed xenon isotopic signatures in solar system reservoirs and possible relationships. The predominant trapped xenon component in ordinary chondrites (OC) is OC-Xe and its isotopic signature differs from Xe in ureilites, in carbonaceous chondrites, in the atmospheres of Earth and Mars, and in the solar wind. Additional minor Xe components were identified in type 3 chondrites and in the metal phase of chondrites. The OC-Xe and ureilite signatures are both consistent with varying mixtures of HL-Xe and slightly mass fractionated solar-type Xe. Xenon in the Martian atmosphere is found to be strongly mass fractionated by 37.7‰ per amu, relative to solar Xe, favoring the heavy isotopes. Xenon in SNC’s from the Martian mantle show admixture of solar-type Xe, which belongs to an elementally strongly fractionated component. The origin of the isotopic signatures of Ne and Xe in the terrestrial atmosphere are discussed in the light of evidence that the Xe isotopic fractionations in the Martian and terrestrial atmospheres are consistent. However, in the terrestrial atmospheric Xe component excesses are observed for132Xe and also for129,131Xe, relative to fractionated solar Xe. The suggested chemically fractionated fission Xe component (CFF-Xe) seems to closely match the above excesses. We discuss models of origin for planetary volatiles and possible processes driving their evolution to present day compositions.