Inward Radial Mixing of Interstellar Water Ices in the Solar Protoplanetary Disk
Résumé
The very wide diversity of asteroid compositions in the main belt suggests significant material transport in the solar
protoplanetary disk and hints at the presence of interstellar ices in hydrated bodies. However, only a few
quantitative estimations of the contribution of interstellar ice in the inner solar system have been reported, leading
to considerable uncertainty about the extent of radial inward mixing in the solar protoplanetary disk 4.56 Ga ago.
We show that the pristine CM chondrite Paris contains primary Ca-carbonates whose O-isotopic compositions
require an 8%–35% contribution from interstellar water. The presence of interstellar water in Paris is confirmed by
its bulk D/H isotopic composition that shows significant D enrichment (D/H = (167 ± 0.2) × 10−6) relative to
the mean D/H of CM chondrites ((145 ± 3) × 10−6) and the putative D/H of local CM water
((82 ± 1.5) × 10−6). These results imply that (i) efficient radial mixing of interstellar ices occurred from the
outer zone of the solar protoplanetary disk inward and that (ii) chondrites accreted water ice grains from increasing
heliocentric distances in the solar protoplanetary disk.
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