Abiotic molecular oxygen production-Ionic pathway from sulfur dioxide.

Abstract

Molecular oxygen, O₂, is vital to life on Earth and possibly also on exoplanets. 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 O₂ from SO₂, a chemical constituent of many planetary atmospheres and one that played an important part on Earth in the Great Oxidation Event. The O₂ production involves dissociative double ionization of SO₂ leading to efficient formation of the [Formula: see text] ion, which can be converted to abiotic O₂ by electron neutralization or by charge exchange. This formation process may contribute substantially to the abundance of O₂ and related ions in planetary atmospheres, such as the Jovian moons Io, Europa, and Ganymede. We suggest that this sort of ionic pathway for the formation of abiotic O₂ involving multiply charged molecular ion decomposition may also exist for other atmospheric and planetary molecules.