Venus' Mass Spectra Show Signs of Disequilibria in the Middle Clouds

TL;DR

This study re-analyzes Venus' middle cloud spectra, revealing chemical disequilibria and potential signs of biological or chemical processes, including phosphine and nitrogen cycle components, suggesting complex chemistry and possible habitability.

Contribution

It provides new interpretations of spectral data indicating disequilibria and potential biosignatures in Venus' clouds, expanding understanding of extraterrestrial atmospheric chemistry.

Findings

Detection of phosphine and other trace gases suggest redox disequilibria.

Presence of nitrogen cycle components like nitrate, nitrite, and ammonia.

Implications for complex chemistry and possible habitability in Venus' clouds.

Abstract

We present a re-examination of mass spectral data obtained from the Pioneer Venus Large Probe Neutral Mass Spectrometer. Our interpretations of differing trace chemical species are suggestive of redox disequilibria in Venus' middle clouds. Assignments to the data (at 51.3 km) include phosphine, hydrogen sulfide, nitrous acid, nitric acid, carbon monoxide, hydrochloric acid, hydrogen cyanide, ethane, and potentially ammonia, chlorous acid, and several tentative PxOy species. All parent ions were predicated upon assignment of corresponding fragmentation products, isotopologues, and atomic species. The data reveal parent ions at varying oxidation states, implying the presence of reducing power in the clouds, and illuminating the potential for chemistries yet to be discovered. When considering the hypothetical habitability of Venus' clouds, the assignments reveal a potential signature of anaerobic phosphorus metabolism (phosphine), an electron donor for anoxygenic photosynthesis (nitrite), and major constituents of the nitrogen cycle (nitrate, nitrite, ammonia, and N2).