2009 Volume 43 Issue 5 Pages e11-e15
Oxygen isotopic compositions of metal grains in a noble-gas-rich chondrite, NWA 801 CR2, have been determined by secondary ion mass spectrometry. The results show bimodal distribution on Δ17O histogram with peaks of Δ17O = 2.3 and -35.0‰. The 16O-rich peak seems to be due to stellar wind from the protosun. The 16O enrichment is comparable with the most 16O-rich value from chondrite constituents. Difference of oxygen isotopic composition of stellar wind between protosun and the present sun implies how self-pollution by planetary embryos during the planet formation epoch have occurred and whether the present solar photosphere preserves the representative composition of the solar system.