Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane
International audience Titan is a unique object in the Solar System: it is the only satellite bearing a dense atmosphere, which shrouds its surface to direct observation at most wavelengths. This atmosphere is subject to intense photochemistry by the solar UV, which constantly depletes its major con...
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ftccsdartic:oai:HAL:hal-01088820v1 2023-05-15T17:40:00+02:00 Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane Choukroun, M. Sotin, C. Janssen, M. A. Le Gall, Alice Jet Propulsion Laboratory (JPL) NASA-California Institute of Technology (CALTECH) San Francisco, United States 2011-12 https://hal.archives-ouvertes.fr/hal-01088820 en eng HAL CCSD hal-01088820 https://hal.archives-ouvertes.fr/hal-01088820 BIBCODE: 2011AGUFM.P33E1805C American Geophysical Union, Fall Meeting 2011 https://hal.archives-ouvertes.fr/hal-01088820 American Geophysical Union, Fall Meeting 2011, Dec 2011, San Francisco, United States. pp.abstract #P33E-1805 [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] info:eu-repo/semantics/conferenceObject Conference papers 2011 ftccsdartic 2020-12-25T21:19:02Z International audience Titan is a unique object in the Solar System: it is the only satellite bearing a dense atmosphere, which shrouds its surface to direct observation at most wavelengths. This atmosphere is subject to intense photochemistry by the solar UV, which constantly depletes its major constituents N2 and CH4. The current CH4 amounts would disappear over periods of 10-100 Myrs, thus requiring replenishment mechanisms to sustain its presence in the atmosphere. The favored scenarios involve cometary impacts and cryovolcanism, the emission of endogenic icy materials to the surface. However, Cassini observations to date show a sparse cratering record, and debated evidence for cryovolcanism in geologically recent times, suggesting the existence of other mechanisms to replenish the atmospheric methane. Cassini observations of the North Pole lakes between 2007 and 2010 show little change in surface area, suggesting that ethane (photolytic product of methane) is their primary constituent since it has a much lower saturation vapor pressure than methane. The current estimated amount of liquid ethane on Titan is much lower than that predicted by atmospheric models. Ethane is therefore to be trapped in the subsurface. Accretion and evolution scenarios predict that the subsurface and the upper crust of Titan most likely consist of methane clathrate hydrates. Interaction of liquid ethane with methane clathrate should result in the substitution of the encaged methane by ethane, and the subsequent release of methane to the atmosphere. Conditions for this substitution are investigated. A kinetic model shows that it can occur over periods much shorter than geologic timescales on Titan. Mass balance calculations then show that this mechanism can be an important source of Titan's atmospheric methane. Based on these results, we propose a new hydrocarbon cycle on Titan, with events of major outgassing (via impacts and cryovolcanism) that are followed by quiescent periods, during which the substitution of methane by ethane ... Conference Object North Pole Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) North Pole Titan ENVELOPE(33.629,33.629,67.560,67.560) |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] |
spellingShingle |
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] Choukroun, M. Sotin, C. Janssen, M. A. Le Gall, Alice Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane |
topic_facet |
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] |
description |
International audience Titan is a unique object in the Solar System: it is the only satellite bearing a dense atmosphere, which shrouds its surface to direct observation at most wavelengths. This atmosphere is subject to intense photochemistry by the solar UV, which constantly depletes its major constituents N2 and CH4. The current CH4 amounts would disappear over periods of 10-100 Myrs, thus requiring replenishment mechanisms to sustain its presence in the atmosphere. The favored scenarios involve cometary impacts and cryovolcanism, the emission of endogenic icy materials to the surface. However, Cassini observations to date show a sparse cratering record, and debated evidence for cryovolcanism in geologically recent times, suggesting the existence of other mechanisms to replenish the atmospheric methane. Cassini observations of the North Pole lakes between 2007 and 2010 show little change in surface area, suggesting that ethane (photolytic product of methane) is their primary constituent since it has a much lower saturation vapor pressure than methane. The current estimated amount of liquid ethane on Titan is much lower than that predicted by atmospheric models. Ethane is therefore to be trapped in the subsurface. Accretion and evolution scenarios predict that the subsurface and the upper crust of Titan most likely consist of methane clathrate hydrates. Interaction of liquid ethane with methane clathrate should result in the substitution of the encaged methane by ethane, and the subsequent release of methane to the atmosphere. Conditions for this substitution are investigated. A kinetic model shows that it can occur over periods much shorter than geologic timescales on Titan. Mass balance calculations then show that this mechanism can be an important source of Titan's atmospheric methane. Based on these results, we propose a new hydrocarbon cycle on Titan, with events of major outgassing (via impacts and cryovolcanism) that are followed by quiescent periods, during which the substitution of methane by ethane ... |
author2 |
Jet Propulsion Laboratory (JPL) NASA-California Institute of Technology (CALTECH) |
format |
Conference Object |
author |
Choukroun, M. Sotin, C. Janssen, M. A. Le Gall, Alice |
author_facet |
Choukroun, M. Sotin, C. Janssen, M. A. Le Gall, Alice |
author_sort |
Choukroun, M. |
title |
Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane |
title_short |
Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane |
title_full |
Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane |
title_fullStr |
Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane |
title_full_unstemmed |
Methane-ethane substitution in subsurface clathrate hydrates as a source of Titan's atmospheric methane |
title_sort |
methane-ethane substitution in subsurface clathrate hydrates as a source of titan's atmospheric methane |
publisher |
HAL CCSD |
publishDate |
2011 |
url |
https://hal.archives-ouvertes.fr/hal-01088820 |
op_coverage |
San Francisco, United States |
long_lat |
ENVELOPE(33.629,33.629,67.560,67.560) |
geographic |
North Pole Titan |
geographic_facet |
North Pole Titan |
genre |
North Pole |
genre_facet |
North Pole |
op_source |
American Geophysical Union, Fall Meeting 2011 https://hal.archives-ouvertes.fr/hal-01088820 American Geophysical Union, Fall Meeting 2011, Dec 2011, San Francisco, United States. pp.abstract #P33E-1805 |
op_relation |
hal-01088820 https://hal.archives-ouvertes.fr/hal-01088820 BIBCODE: 2011AGUFM.P33E1805C |
_version_ |
1766140777401942016 |