Volcanically extruded phosphides as an abiotic source of Venusian phosphine

We hypothesize that trace amounts of phosphides formed in the mantle are a plausible abiotic source of the Venusian phosphine observed by Greaves et al. [ , https://doi.org/10.1038/s41550-020-1174-4 (2020)]. In this hypothesis, small amounts of phosphides (P bound in metals such as iron), sourced fr...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 118; no. 29; p. 1
Main Authors Truong, N, Lunine, J I
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 20.07.2021
Subjects
Earth mantle
Extrusion
Heavy metals
Magma
Phosphides
Phosphine
Phosphines
Physical Sciences
Planetary mantles
Plate tectonics
Redox properties
Remote sensing
Sulfur
Sulfur dioxide
Sulfuric acid
Tectonics
Venus
Volcanic activity
Volcanic eruptions
Venus
phosphine
volcanism
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Summary:We hypothesize that trace amounts of phosphides formed in the mantle are a plausible abiotic source of the Venusian phosphine observed by Greaves et al. [ , https://doi.org/10.1038/s41550-020-1174-4 (2020)]. In this hypothesis, small amounts of phosphides (P bound in metals such as iron), sourced from a deep mantle, are brought to the surface by volcanism. They are then ejected into the atmosphere in the form of volcanic dust by explosive volcanic eruptions, which were invoked by others to explain the episodic changes of sulfur dioxide seen in the atmosphere [Esposito, 223, 1072-1074 (1984)]. There they react with sulfuric acid in the aerosol layer to form phosphine (2 P + 3H SO = 2PH + 3SO ). We take issue with the conclusion of Bains et al. [arXiv:2009.06499 (2020)] that the volcanic rates for such a mechanism would have to be implausibly high. We consider a mantle with the redox state similar to the Earth, magma originating deep in the mantle-a likely scenario for the origin of plume volcanism on Venus-and episodically high but plausible rates of volcanism on a Venus bereft of plate tectonics. We conclude that volcanism could supply an adequate amount of phosphide to produce phosphine. Our conclusion is supported by remote sensing observations of the Venusian atmosphere and surface that have been interpreted as indicative of currently active volcanism.
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Reviewers: J.F.K., Penn State University; S.S., Jet Propulsion Laboratory; L.W.E., University of Colorado at Boulder; and P.K.B., North Carolina State University.
Author contributions: J.I.L. designed research; N.T. and J.I.L. performed research; and N.T. and J.I.L. wrote the paper.
Contributed by J. I. Lunine, June 8, 2021 (sent for review October 16, 2020; reviewed by James F. Kasting, Suzanne Smrekar, Larry W. Esposito, and Paul K. Byrne)
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2021689118