Solar XUV and ENA-driven water loss from early Venus' steam atmosphere

Тип публикации: статья из журнала

Год издания: 2016

Идентификатор DOI: 10.1002/2015JA022226

Ключевые слова: energetic neutral atoms, atmosphere evolution, Venus, atmosphere evolution, energetic neutral atoms, Venus

Аннотация: We present a study on the influence of the upper atmosphere hydrodynamic escape of hydrogen, driven by the solar soft X-ray and extreme ultraviolet radiation (XUV), on an expected outgassed steam atmosphere of early Venus. By assuming that the young Sun was either a weak or moderately active young G star, we estimated the water loss from a hydrogen dominated thermosphere due to the absorption of the solar XUV flux and the precipitation of solar wind produced energetic hydrogen atoms (ENAs). The production of ENAs and their interaction with the hydrodynamic extended upper atmosphere, including collision-related feedback processes, have been calculated by means of Monte Carlo models. ENAs that collide in the upper atmosphere deposit their energy and heat the surrounding atmosphere mainly above the main XUV energy deposition layer. It is shown that precipitating ENAs modify the thermal structure of the upper atmosphere, but the enhancement of the thermal escape rates caused by these energetic hydrogen atoms is negligible. Our results also indicate that the majority of oxygen arising from dissociated H2O molecules is left behind during the first 100Myr. It is thus suggested that the main part of the remaining oxygen has been absorbed by crustal oxidation.

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Издание

Журнал: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS

Выпуск журнала: Vol. 121, Is. 5

Номера страниц: 4718-4732

ISSN журнала: 21699380

Место издания: WASHINGTON

Издатель: AMER GEOPHYSICAL UNION

Авторы

  • Lichtenegger H.I.M. (Austrian Acad Sci, Space Res Inst, Graz, Austria)
  • Kislyakova K.G. (Austrian Acad Sci, Space Res Inst, Graz, Austria)
  • Odert P. (Austrian Acad Sci, Space Res Inst, Graz, Austria)
  • Erkaev N.V. (SB RAS, Inst Computat Modelling, Krasnoyarsk, Russia; Siberian Fed Univ, Polytech Inst, Krasnoyarsk, Russia)
  • Lammer H. (Austrian Acad Sci, Space Res Inst, Graz, Austria)
  • Groller H. (Univ Arizona, Dept Planetary Sci, Tucson, AZ 85721 USA)
  • Johnstone C.P. (Univ Vienna, Dept Astrophys, Vienna, Austria)
  • Elkins-Tanton L. (Arizona State Univ, Sch Earth & Space Explorat, Tempe, AZ USA)
  • Tu L. (Univ Vienna, Dept Astrophys, Vienna, Austria)
  • Guedel M. (Univ Vienna, Dept Astrophys, Vienna, Austria)
  • Holmstrom M. (Swedish Inst Space Phys, Kiruna, Sweden)

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