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arXiv · 2505.16692

Increased hydrogen escape from Mars atmosphere during periods of high obliquity

Gabriella Gilli·Francisco González-Galindo·Jean-Yves Chaufray·Ehouarn Millour·François Forget·Franck Montmessin·Franck Lefèvre·Joseph Naar·Yangcheng Luo·Margaux Vals·Loïc Rossi·Miguel Ángel López-Valverde·Adrián Brines
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Abstract

It is still unknown how much water has escaped from Mars during its history. Hydrogen escape from Mars's atmosphere probably played a major role in drying the planet, but present-day Hloss rates (about 3x10^26 atoms per second on average) cannot explain the geological evidence for the large volumes of liquid water on ancient Mars. Here we used the three-dimensional Mars-Planetary Climate Model to show that H loss rates could have increased by more than one order of magnitude (6x10^27 atoms per second) during higher spin axis obliquity periods, notably in the last few million years when Mars's obliquity was about 35 deg on average. The resulting accumulated H escape over Mars's history translates into an approx. 80 m global equivalent layer, which is close to the lower limit of geological estimates, assessing the major role of atmospheric escape in drying Mars.

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Gabriella Gilli, Francisco González-Galindo, Jean-Yves Chaufray, Ehouarn Millour, François Forget, Franck Montmessin, Franck Lefèvre, Joseph Naar, Yangcheng Luo, Margaux Vals, Loïc Rossi, Miguel Ángel López-Valverde, Adrián Brines. 2025-05-22. Increased hydrogen escape from Mars atmosphere during periods of high obliquity. https://doi.org/10.1038/s41550-025-02561-3

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