The deep oxygen abundance in Solar System Giant Planets, with a new derivation for Saturn

TL;DR

This paper reviews current methods and constraints on measuring the deep oxygen abundance in Solar System giant planets, highlighting its importance for understanding their internal structure, evolution, and formation.

Contribution

It provides a comprehensive review of observational and thermochemical modeling approaches to determine deep oxygen levels in giant planets, including a new derivation for Saturn.

Findings

Deep oxygen abundance constrains planetary interior models.

Water's role in atmospheric meteorology affects oxygen measurement.

New derivation improves Saturn's oxygen abundance estimate.

Abstract

Deep elemental composition is a challenging measurement to achieve in the giant planets of the solar system. Yet, knowledge of the deep composition offers important insights in the internal structure of these planets, their evolutionary history and their formation scenarios. A key element whose deep abundance is difficult to obtain is oxygen, because of its propensity for being in condensed phases such as rocks and ices. In the atmospheres of the giant planets, oxygen is largely stored in water molecules that condense below the observable levels. At atmospheric levels that can be investigated with remote sensing, water abundance can modify the observed meteorology, and meteorological phenomena can distribute water through the atmosphere in complex ways that are not well understood and that encompass deeper portions of the atmosphere. The deep oxygen abundance provides constraints on the connection between atmosphere and interior and on the processes by which other elements were trapped, making its determination an important element to understand giant planets. In this paper, we review the current constraints on the deep oxygen abundance of the giant planets, as derived from observations and thermochemical models.