Nebular water depletion as the cause of Jupiter's low oxygen abundance

TL;DR

This paper proposes that Jupiter's low oxygen abundance results from formation in an oxygen-depleted, carbon-rich disk, challenging traditional models and aligning with recent spectroscopic data and thermochemical predictions.

Contribution

It introduces a model where Jupiter forms in a C/O~1 disk, explaining its composition and predicting a lower oxygen enrichment than previous models.

Findings

Jupiter's composition is consistent with formation in a carbon-rich, oxygen-depleted disk.

Jupiter's oxygen abundance is predicted to be about twice solar, not seven times.

The model's predictions can be tested by upcoming Juno mission measurements.

Abstract

Motivated by recent spectroscopic observations suggesting that atmospheres of some extrasolar giant-planets are carbon-rich, i.e. carbon/oxygen ratio (C/O) $\ge$ 1, we find that the whole set of compositional data for Jupiter is consistent with the hypothesis that it be a carbon-rich giant planet. We show that the formation of Jupiter in the cold outer part of an oxygen-depleted disk (C/O $\sim$1) reproduces the measured Jovian elemental abundances at least as well as the hitherto canonical model of Jupiter formed in a disk of solar composition (C/O = 0.54). The resulting O abundance in Jupiter's envelope is then moderately enriched by a factor of $\sim$2 $\times$ solar (instead of $\sim$7 $\times$ solar) and is found to be consistent with values predicted by thermochemical models of the atmosphere. That Jupiter formed in a disk with C/O $\sim$1 implies that water ice was heterogeneously distributed over several AU beyond the snow line in the primordial nebula and that the fraction of water contained in icy planetesimals was a strong function of their formation location and time. The Jovian oxygen abundance to be measured by NASA's Juno mission en route to Jupiter will provide a direct and strict test of our predictions.