Computer Science
Scientific paper
Feb 1982
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982natur.295..643k&link_type=abstract
Nature, vol. 295, Feb. 25, 1982, p. 643, 644.
Computer Science
7
Abundance, Cosmochemistry, Isotopic Enrichment, Lunar Composition, Meteoritic Composition, Nitrogen 15, Chemical Composition, Chemical Fractionation, Gamma Rays, Interstellar Chemistry, Protostars, Selenology, Solar Radiation, Solar System
Scientific paper
Models for mechanisms which cause the widely varying N-15/N-14 stable isotope ratios observed in meteoritic and lunar samples are discussed. Interstellar ionization has been observed to be insufficient to account for the fractionations seen in the samples, which vary by as much as 5% from what is judged to be remnants of protosolar nebular material. An upper limit of less than -21% is suggested for the protosolar ratio, which implies a production of N-15 in surface regions of the sun, although gamma ray flux measurements of the sun indicate that the levels of nuclear activity are too low to form satisfactory quantities of N-15. The addition of N-15 by alien matter is not supportable due to the paucity of N-15 in the interstellar medium. Spacecraft measurements have also cast doubt on an influx due to solar wind ejection, and it is noted that the Galileo mission to Jupiter may resolve the estimates of the protosolar N-15/N-14 ratio because no net fractionation would have occurred during accretion by Jupiter, thereby leaving all Jovian nitrogen bound up in NH3.
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