|Title:||Existence of an 16O‐rich gaseous reservoir in the solar nebula|
|Authors:||A. N. Krot, K. D. McKeegan, L. A. Leshin, G. J. MacPherson, and E. R. D. Scott|
|Publication:||Science, v. 295, p. 1051‐1054.|
|Publish Date:||Feb 2002|
Carbonaceous chondrite condensate olivine grains from two distinct petrographic settings, calcium‐aluminum‐rich inclusion (CAI) accretionary rims and amoeboid olivine aggregates (AOAs), are oxygen‐16 (16O) enriched at the level previously observed inside CAIs. This requires that the gas in the nebular region where these grains condensed was 16O−rich. This contrasts with an 16O−poor gas present during the formation of chondrules, suggesting that CAIs and AOAs formed in a spatially restricted region of the solar nebula containing 16O−rich gas. The 16O‐rich gas composition may have resulted either from mass‐independent isotopic chemistry or from evaporation of regions with enhanced dust/gas ratios, possibly in an X‐wind environment near the young Sun.