ApJl, volume 507, L185-188
Phys. Chem. Earth in press
Using the high-resolution mass spectrometer CELIAS/MTOF on board SOHO we have determined the solar wind isotope abundance ratio of N, 14N/15N = 200±60, indicating a depletion of 15N in the terrestrial atmosphere compared to solar matter. This result is compatible with the hypothesis that terrestrial N and also N found in lunar surface material is a mixture of a heavy component identical with solar N and an unspecified light component. The large variations of 14N/15N in solar system matter is caused by special isotope enrichment processes as in the case of Mars as well as by varying mixtures of isotopically different components.