Measuring the level of interstellar inheritance in the solar protoplanetary disk

1Conel M. O’D. Alexander,1Larry R. Nittler,1Jemma Davidson,2Fred J. Ciesla
Meteoritcs & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12891]
1Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC, USA
2Department of Geophysical Sciences, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois, USA
Published by arrangement with John Wiley & Sons

The timing and extent to which the initial interstellar material was thermally processed provide fundamental constraints for models of the formation and early evolution of the solar protoplanetary disk. We argue that the nonsolar (solar Δ17O ≈ −29‰) and near-terrestrial (Δ17O ≈ 0‰) O-isotopic compositions of the Earth and most extraterrestrial materials (Moon, Mars, asteroids, and comet dust) were established very early by heating of regions of the disk that were modestly enriched (dust/gas ≥ 5–10 times solar) in primordial silicates (Δ17O ≈ −29‰) and water-dominated ice (Δ17O ≈ 24‰) relative to the gas. Such modest enrichments could be achieved by grain growth and settling of dust to the midplane in regions where the levels of turbulence were modest. The episodic heating of the disk associated with FU Orionis outbursts were the likely causes of this early thermal processing of dust. We also estimate that at the time of accretion the CI chondrite and interplanetary dust particle parent bodies were composed of ~5–10% of pristine interstellar material. The matrices of all chondrites included roughly similar interstellar fractions. Whether this interstellar material avoided the thermal processing experienced by most dust during FU Orionis outbursts or was accreted by the disk after the outbursts ceased to be important remains to be established.

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