What is it about?
Thanks to observations made by the Solar Occultation in the Infrared (SOIR) instrument onboard the Venus Express space probe of the European Space Agency (ESA), researchers have revealed an unanticipated increase in the abundances of two variants of water molecules – H2O and HDO – along with their ratio HDO/H2O, in the Venus mesosphere. This unexpected phenomenon questions our current knowledge of the history of water on Venus and the factors that may or may not have favoured planetary habitability in the past. This breakthrough is based on the identification of a possible mechanism.
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Why is it important?
Our study highlights two important key points. First, a thorough understanding of altitude variations is essential for locating deuterium and hydrogen reservoirs in Venus’s atmosphere, providing a better understanding of the history of water on the planet. Second, increased HDO/H2O isotope ratio impacts hydrogen and deuterium escape rates. Photolysis of H2O and HDO at higher altitudes leads to an increased deuterium release, thus influencing the long-term evolution of the D/H ratio.
Perspectives
These findings encourage incorporating altitude-dependent processes into models to make accurate predictions about D/H evolution and to reassess whether ancient Venus was wetter or dryer than previously thought, thus influencing its past habitability.
Arnaud Mahieux
Institut Royal d'Aéronomie Spatiale de Belgique
Read the Original
This page is a summary of: Unexpected increase of the deuterium to hydrogen ratio in the Venus mesosphere, Proceedings of the National Academy of Sciences, August 2024, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2401638121.
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