Venus water loss is dominated by HCO + dissociative recombination.

Autor: Chaffin MS; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA. michael.chaffin@colorado.edu., Cangi EM; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA., Gregory BS; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA., Yelle RV; Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA., Deighan J; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA., Elliott RD; Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA., Gröller H; Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
Jazyk: angličtina
Zdroj: Nature [Nature] 2024 May; Vol. 629 (8011), pp. 307-310. Date of Electronic Publication: 2024 May 06.
DOI: 10.1038/s41586-024-07261-y
Abstrakt: Despite its Earth-like size and source material 1,2 , Venus is extremely dry 3,4 , indicating near-total water loss to space by means of hydrogen outflow from an ancient, steam-dominated atmosphere 5,6 . Such hydrodynamic escape likely removed most of an initial Earth-like 3-km global equivalent layer (GEL) of water but cannot deplete the atmosphere to the observed 3-cm GEL because it shuts down below about 10-100 m GEL 5,7 . To complete Venus water loss, and to produce the observed bulk atmospheric enrichment in deuterium of about 120 times Earth 8,9 , nonthermal H escape mechanisms still operating today are required 10,11 . Early studies identified these as resonant charge exchange 12-14 , hot oxygen impact 15,16 and ion outflow 17,18 , establishing a consensus view of H escape 10,19 that has since received only minimal updates 20 . Here we show that this consensus omits the most important present-day H loss process, HCO + dissociative recombination. This process nearly doubles the Venus H escape rate and, consequently, doubles the amount of present-day volcanic water outgassing and/or impactor infall required to maintain a steady-state atmospheric water abundance. These higher loss rates resolve long-standing difficulties in simultaneously explaining the measured abundance and isotope ratio of Venusian water 21,22 and would enable faster desiccation in the wake of speculative late ocean scenarios 23 . Design limitations prevented past Venus missions from measuring both HCO + and the escaping hydrogen produced by its recombination; future spacecraft measurements are imperative.
(© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)
Databáze: MEDLINE
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