Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere
International audience Revealed by the Cassini and Voyager Missions, a plethora of volatile species are formed in Titan's upper atmosphere from the initial N 2 /CH 4 (~98/2%) composition. As they precipitate, most of the volatiles condense in the colder lower atmosphere where they can form icy...
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ftsorbonneuniv:oai:HAL:hal-01796628v1 2023-11-05T03:45:08+01:00 Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere Dubois, David Gudipati, Murthy, S. Carrasco, Nathalie PLANETO - LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS) Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS) Jet Propulsion Laboratory (JPL) NASA-California Institute of Technology (CALTECH) Boulder, United States 2018-08-12 https://hal.science/hal-01796628 en eng HAL CCSD hal-01796628 https://hal.science/hal-01796628 Cassini Science Symposium 2018 https://hal.science/hal-01796628 Cassini Science Symposium 2018, Aug 2018, Boulder, United States [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology info:eu-repo/semantics/conferenceObject Conference papers 2018 ftsorbonneuniv 2023-10-10T23:59:28Z International audience Revealed by the Cassini and Voyager Missions, a plethora of volatile species are formed in Titan's upper atmosphere from the initial N 2 /CH 4 (~98/2%) composition. As they precipitate, most of the volatiles condense in the colder lower atmosphere where they can form icy clouds (e.g. C 4 N 2 , HCN, C 2 H 6 ) which have been detected above the poles. HCN is the most abundant nitrile in Titan's atmosphere and suspected to condensate in Titan's lower stratosphere (typically <100 km). Micron-sized HCN ice particles were also observed above the south pole at high altitudes (300 km). This cloud is thought to have been formed in the post-equinox winter polar vortex. In the north polar regions, HCN is also a likely prominent contributor to the haystack spectral signature seen at 221 cm -1 . These stratospheric ices may contribute as condensation nuclei for ices deeper down in the troposphere. Furthermore, C 4 H 2 , a simple alkyne formed by the chemistry and relatively abundant in the stratosphere, condenses near 75 km, lower than HCN. C 4 H 2 can also absorb the lesser energetic photos at these low altitudes, forming the radical C 4 H which then reacts with CH 4 , causing the consumption of methane. Consequently, the loss mechanism for C 4 H 2 is photo-chemistry. As soon as C 4 H 2 condenses, small molecule and complex accretion with HCN may occur. The reactive state that these ices may undergo with long-UV radiation after they form is still largely unknown. We explore these conditions by studying HCN-C 4 H 2 ice mixtures in the laboratory, by using the Titan Organic Aerosol Spectroscopy and chemisTry (TOAST) setup at JPL's Ice Spectroscopy Laboratory (ISL). These ices are then irradiated at long-UV wavelengths pertaining to these low-altitude regions at low-controlled temperatures. The residue is analyzed using long-IR absorption. Our results show a solid-state HCN consumption due to irradiation, to which C 4 H 2 acts as a catalyst, indicating HCN ice particle ageing in the troposphere may ... Conference Object South pole HAL Sorbonne Université |
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Open Polar |
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HAL Sorbonne Université |
op_collection_id |
ftsorbonneuniv |
language |
English |
topic |
[SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology |
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[SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology Dubois, David Gudipati, Murthy, S. Carrasco, Nathalie Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere |
topic_facet |
[SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology |
description |
International audience Revealed by the Cassini and Voyager Missions, a plethora of volatile species are formed in Titan's upper atmosphere from the initial N 2 /CH 4 (~98/2%) composition. As they precipitate, most of the volatiles condense in the colder lower atmosphere where they can form icy clouds (e.g. C 4 N 2 , HCN, C 2 H 6 ) which have been detected above the poles. HCN is the most abundant nitrile in Titan's atmosphere and suspected to condensate in Titan's lower stratosphere (typically <100 km). Micron-sized HCN ice particles were also observed above the south pole at high altitudes (300 km). This cloud is thought to have been formed in the post-equinox winter polar vortex. In the north polar regions, HCN is also a likely prominent contributor to the haystack spectral signature seen at 221 cm -1 . These stratospheric ices may contribute as condensation nuclei for ices deeper down in the troposphere. Furthermore, C 4 H 2 , a simple alkyne formed by the chemistry and relatively abundant in the stratosphere, condenses near 75 km, lower than HCN. C 4 H 2 can also absorb the lesser energetic photos at these low altitudes, forming the radical C 4 H which then reacts with CH 4 , causing the consumption of methane. Consequently, the loss mechanism for C 4 H 2 is photo-chemistry. As soon as C 4 H 2 condenses, small molecule and complex accretion with HCN may occur. The reactive state that these ices may undergo with long-UV radiation after they form is still largely unknown. We explore these conditions by studying HCN-C 4 H 2 ice mixtures in the laboratory, by using the Titan Organic Aerosol Spectroscopy and chemisTry (TOAST) setup at JPL's Ice Spectroscopy Laboratory (ISL). These ices are then irradiated at long-UV wavelengths pertaining to these low-altitude regions at low-controlled temperatures. The residue is analyzed using long-IR absorption. Our results show a solid-state HCN consumption due to irradiation, to which C 4 H 2 acts as a catalyst, indicating HCN ice particle ageing in the troposphere may ... |
author2 |
PLANETO - LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS) Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS) Jet Propulsion Laboratory (JPL) NASA-California Institute of Technology (CALTECH) |
format |
Conference Object |
author |
Dubois, David Gudipati, Murthy, S. Carrasco, Nathalie |
author_facet |
Dubois, David Gudipati, Murthy, S. Carrasco, Nathalie |
author_sort |
Dubois, David |
title |
Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere |
title_short |
Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere |
title_full |
Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere |
title_fullStr |
Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere |
title_full_unstemmed |
Photochemical activity of HCN-C 4 H 2 ices in Titan's lower atmosphere |
title_sort |
photochemical activity of hcn-c 4 h 2 ices in titan's lower atmosphere |
publisher |
HAL CCSD |
publishDate |
2018 |
url |
https://hal.science/hal-01796628 |
op_coverage |
Boulder, United States |
genre |
South pole |
genre_facet |
South pole |
op_source |
Cassini Science Symposium 2018 https://hal.science/hal-01796628 Cassini Science Symposium 2018, Aug 2018, Boulder, United States |
op_relation |
hal-01796628 https://hal.science/hal-01796628 |
_version_ |
1781706565867274240 |