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

Abstract:

We present a re-examination of published mass spectral data obtained from the Pioneer Venus Large Probe Neutral Mass Spectrometer (51.3 km). Our interpretations support the presence of minor chemical species that are suggestive of disequilibria in Venus’ middle clouds. Assignments to the data include phosphine and/or overlapping hydrogen sulfide, nitrous acid, nitric acid, ammonium, carbon monoxide, ethane, hydrochloric acid, and potentially benzene, methane, ethene, and chlorous acid. Chemical assignments were predicated upon matching parent ions to fragmentation products, and atomic elements to parent ions. The data reveal parent ions at varying oxidation states, implying the presence of reducing power in the clouds. Interestingly, when considering the potential habitability of Venus’ clouds, the assignments reveal a potential electron donor for anoxygenic photosynthesis (nitrite), and all major constituents of the nitrogen cycle (nitrate, nitrite, possibly ammonium, N₂). Our mass assignments illuminate the potential for chemistries yet to be discovered on Venus.