Oxygen Isotope Constraints on the Importance of Photochemical Processing in Protoplanetary Disks

TL;DR

This study uses oxygen isotopic data and modeling to assess the impact of photochemical processing in protoplanetary disks, concluding it is inherited from molecular clouds and has minimal influence on planetary compositions.

Contribution

It provides a quantitative analysis showing photochemical processing in disks does not significantly alter planetary compositions, emphasizing inheritance from molecular clouds.

Findings

Oxygen isotopic evolution is inherited from molecular clouds.

Photochemical processing in disks has minimal impact on planetary compositions.

Modeling indicates the observed isotopic diversity predates disk processing.

Abstract

Observations have revealed evidence of photochemical processing in protoplanetary disks. This processing occurs in the photon dominated layer, the optically thin regions of the disk high above the disk midplane. It remains unclear, however, how much this photochemical processing impacts the compositions of the planets and their building blocks within the disk. Here we use the oxygen isotopic compositions of Solar System solids, which has been attributed to photochemistry in the solar nebula, to quantitatively evaluate whether this processing could have produced the conditions needed to provide the diversity of compositions seen in the Solar System. We do this by modeling the chemical evolution while fine dust grows into the building blocks of the planets. We find that the oxygen isotopic evolution cannot be attributed to processing in the solar nebula and must instead be inherited from the parent molecular cloud. Further, our results indicate that the observed photochemical processing in protoplanetary disks does not significantly impact the compositions of planets that form within.