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<p>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 H loss rates (~3 × 10<sup>26</sup> 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 (6 × 10<sup>27</sup> atoms per second) during higher spin axis obliquity periods, notably in the last few million years when Mars’s obliquity was about 35° on average. The resulting accumulated H escape over Mars’s history translates into an ~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.</p>

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Increased hydrogen escape from Mars atmosphere during periods of high obliquity

  • 期刊论文

  • 发表日期：

    2025年5月21日

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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

摘要

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 H loss rates (~3 × 1026 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 (6 × 1027 atoms per second) during higher spin axis obliquity periods, notably in the last few million years when Mars’s obliquity was about 35° on average. The resulting accumulated H escape over Mars’s history translates into an ~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.