Origin of Nucleosynthetic Isotope Heterogeneity in the Solar Protoplanetary Disk
Anne Trinquier,1
Tim Elliott,2
David Ulfbeck,1
Christopher Coath,2
Alexander N. Krot,1,3
Martin Bizzarro1*
Stable-isotope variations exist among inner solar system solids,
planets, and asteroids, but their importance is not understood.
We report correlated, mass-independent variations of titanium-46
and titanium-50 in bulk analyses of these materials. Because
titanium-46 and titanium-50 have different nucleosynthetic origins,
this correlation suggests that the presolar dust inherited from
the protosolar molecular cloud was well mixed when the oldest
solar system solids formed, but requires a subsequent process
imparting isotopic variability at the planetary scale. We infer
that thermal processing of molecular cloud material, probably
associated with volatile-element depletions in the inner solar
system, resulted in selective destruction of thermally unstable,
isotopically anomalous presolar components, producing residual
isotopic heterogeneity. This implies that terrestrial planets
accreted from thermally processed solids with nonsolar isotopic
compositions.
2 Bristol Isotope Group, Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK.
3 Hawai'i Institute of Geophysics and Planetology, University of Hawai'i at Manoa, HI 96822, USA.
* To whom correspondence should be addressed. E-mail: bizzarro{at}snm.ku.dk
