Abiotic molecular oxygen production -- ionic pathway from sulphur dioxide

TL;DR

This study provides experimental and theoretical evidence for an ionic pathway where SO$_2$ dissociative double ionisation leads to abiotic O$_2$ production, impacting planetary atmospheres' oxygen levels.

Contribution

It introduces a novel ionic mechanism for abiotic O$_2$ formation from SO$_2$, supported by combined experimental and theoretical analysis.

Findings

O$_2$ can be produced abiotically via SO$_2$ ionisation.

The process involves dissociative double ionisation of SO$_2$.

This mechanism may significantly influence planetary atmospheric oxygen levels.

Abstract

Molecular oxygen, O$_2$, is vital to life on Earth and possibly on other planets. Although the biogenic processes leading to its accumulation in Earth's atmosphere are well understood, its abiotic origin is still not fully established. Here, we report combined experimental and theoretical evidence for electronic-state-selective production of O$_2$ from SO$_2$, a major chemical constituent of many planetary atmospheres and one which played an important part on Earth in the Great Oxidation event. The O$_2$ production involves dissociative double ionisation of SO$_2$ leading to efficient formation of the O$_2^+$ ion which can be converted to abiotic O$_2$ by electron neutralisation. We suggest that this formation process may contribute significantly to the abundance of O$_2$ and related ions in planetary atmospheres, especially in those where CO$_2$, which can lead to O$_2$ production by different mechanisms, is not the dominant component.