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Communication Dans Un Congrès Année : 2021

The Martian D/H Ratio In Escaping Atoms and Evidence for Primordial Water

Résumé

A key indicator of the amount of martian water lost into space is the ratio of the isotopes deuterium to hydrogen in the present-day atmosphere. The constituent atoms of water are known to escape into space, with H escaping rapidly from the Jeans process of thermal evaporation and O escaping by different superthermal processes. The lighter isotope H escapes faster than D leading to a gradual increase in the D/H ratio of the remaining water. The present D/H ratio is proportional to the total amount of water that has escaped, but deriving the depth of water on a warmer and wetter primordial Mars requires understanding the factors that control escape processes today. Observations of UV line emissions from H and D atoms has been carried out with an echelle channel in the IUVS instrument on the MAVEN mission, providing direct measurements of the H and D densities and escape rates from the upper martian atmosphere. Both H and D are highly variable over the course of a martian year, with strong seasonal changes in the densities and the D/H ratio of escaping atoms. In addition the ratio D/H in the escaping atoms varies over the year, i.e. the fractionation factor is not constant. The consequences for the history of H and D and water escape will be discussed.
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Dates et versions

insu-04440234 , version 1 (05-02-2024)

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John Clarke, Majd Mayyasi, Dolon Bhattacharyya, Nicholas Schneider, Bruce Jakosky, et al.. The Martian D/H Ratio In Escaping Atoms and Evidence for Primordial Water. AGU Fall Meeting 2021, Dec 2021, New Orleans, United States. pp.id. P33B-08. ⟨insu-04440234⟩
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