Сибирский федеральный университет

Тип публикации: статья из журнала

Год издания: 2021

Идентификатор DOI: 10.1093/mnras/staa3151

Ключевые слова: hydrodynamics, methods: numerical, sun: evolution, sun: uv radiation, planets and satellites: atmospheres, planets and satellites: physical evolution

Аннотация: We apply a 1D upper atmosphere model to study thermal escape of nitrogen over Titan's history. Significant thermal escape should have occurred very early for solar extreme ultraviolet (EUV) fluxes 100-400 times higher than today with escape rates as high as approximate to 1.5 x 10(28) s(-1) and approximate to 4.5 x 10(29) s(-1), respectively, while today it is similar to 7.5 x 10(17) s(-1). Depending on whether the Sun originated as a slow, moderate, or fast rotator, thermal escape was the dominant escape process for the first 100-1000 Myr after the formation of the Solar system. If Titan's atmosphere originated that early, it could have lost between approximate to 0.5 and 16 times its present atmospheric mass depending on the Sun's rotational evolution. We also investigated the mass-balance parameter space for an outgassing of Titan's nitrogen through decomposition of NH3-ices in its deep interior. Our study indicates that, if Titan's atmosphere originated at the beginning, it could have only survived until today if the Sun was a slow rotator. In other cases, the escape would have been too strong for the degassed nitrogen to survive until present day, implying later outgassing or an additional nitrogen source. An endogenic origin of Titan's nitrogen partially through NH3-ices is consistent with its initial fractionation of N-14/N-15 approximate to 166-172, or lower if photochemical removal was relevant for longer than the last approximate to 1000 Myr. Since this ratio is slightly above the ratio of cometary ammonia, some of Titan's nitrogen might have originated from refractory organics.

Журнал: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Выпуск журнала: Vol. 500, Is. 2

Номера страниц: 2020-2035

ISSN журнала: 00358711

Место издания: OXFORD

Издатель: OXFORD UNIV PRESS

• Erkaev N.V (Russian Acad Sci, Inst Computat Modelling, Siberian Branch, Krasnoyarsk 660036, Russia; Siberian Fed Univ, Appl Mech Dept, Krasnoyarsk 660074, Russia; Russian Acad Sci, Inst Laser Phys, Siberian Branch, Novosibirsk 630090, Russia)
• Scherf M. (Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria)
• Thaller S.E. (Karl Franzens Univ Graz, Inst Phys IGAM, A-8010 Graz, Austria)
• Lammer H. (Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria)
• Mezentsev A.V (Siberian Fed Univ, Appl Mech Dept, Krasnoyarsk 660074, Russia)
• Ivanov V.A. (Siberian Fed Univ, Appl Mech Dept, Krasnoyarsk 660074, Russia)
• Mandt K.E. (Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA)

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