  We present osmium isotopic results obtained by sequential leaching of the
Murchison meteorite, which reveal the existence of very large internal
anomalies of nucleosynthetic origin. The Os isotopic anomalies are correlated,
and can be explained by the variable contributions of components derived from
the s, r and p-processes of nucleosynthesis. Much of the s-process rich osmium
is released by relatively mild leaching, suggesting the existence of an easily
leachable s-process rich presolar phase, or alternatively, of a chemically
resistant r-process rich phase. The s-process composition of Os released by
mild leaching diverges slightly from that released by aggressive digestion
techniques, perhaps suggesting that the presolar phases attacked by these
differing procedures condensed in different stellar environments. The
correlation between 190Os and 188Os can be used to constrain the s-process
190Os/188Os ratio to be 1.275 pm 0.043. Such a ratio can be reproduced in a
nuclear reaction network for a MACS value for 190Os of ~200 pm 22 mbarn at 30
keV. We also present evidence for extensive internal variation of 184Os
abundances in the Murchison meteorite. This suggests that p process rich
presolar grains (e.g., supernova condensates) may be present in meteorites in
sufficient quantities to influence the Os isotopic compositions of the
leachates.
