Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice
We report the detection of a spectral signature observed at 682 cm−1 by the Cassini Composite Infrared Spectrometer (CIRS) in nadir and limb geometry observations of Titan's southern stratospheric polar region in the middle of southern fall, while stratospheric temperatures are the coldest sinc...
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ftunivwagenin:oai:library.wur.nl:wurpubs/583058 2024-01-14T10:10:47+01:00 Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice Vinatier, S. Schmitt, B. Bézard, B. Rannou, P. Dauphin, C. de Kok, R. Jennings, D.E. Flasar, F.M. 2018 text/html https://research.wur.nl/en/publications/study-of-titans-fall-southern-stratospheric-polar-cloud-compositi https://doi.org/10.1016/j.icarus.2017.12.040 en eng https://edepot.wur.nl/547897 https://research.wur.nl/en/publications/study-of-titans-fall-southern-stratospheric-polar-cloud-compositi doi:10.1016/j.icarus.2017.12.040 info:eu-repo/semantics/restrictedAccess Wageningen University & Research Icarus 310 (2018) ISSN: 0019-1035 Atmospheres composition structures Infrared observations Titan atmosphere info:eu-repo/semantics/article Article/Letter to editor info:eu-repo/semantics/publishedVersion 2018 ftunivwagenin https://doi.org/10.1016/j.icarus.2017.12.040 2023-12-20T23:16:35Z We report the detection of a spectral signature observed at 682 cm−1 by the Cassini Composite Infrared Spectrometer (CIRS) in nadir and limb geometry observations of Titan's southern stratospheric polar region in the middle of southern fall, while stratospheric temperatures are the coldest since the beginning of the Cassini mission. In the same period, many gases observed in CIRS spectra (C2H2, HCN, C4H2, C3H4, HC3N and C6H6) are highly enriched in the stratosphere at high southern latitude due to the air subsidence of the global atmospheric circulation and some of these molecules condense at much higher altitude than usually observed for other latitudes. The 682 cm−1 signature, which is only observed below an altitude of 300 km, is at least partly attributed to the benzene (C6H6) ice ν4 C–H bending mode. While we first observed it in CIRS nadir spectra of the southern polar region in early 2013, we focus here on the study of nadir data acquired in May 2013, which have a more favorable observation geometry. We derived the C6H6 ice mass mixing ratio in 5° latitude bins from the south pole to 65°S and infer the C6H6 cloud top altitude to be located deeper with increasing distance from the pole. We additionally analyzed limb data acquired in March 2015, which were the first limb dataset available after the May 2013 nadir observation, in order to infer a vertical profile of its mass mixing ratio in the 0.1–1 mbar region (250–170 km). We derive an upper limit of ∼1.5 µm for the equivalent radius of pure C6H6 ice particles from the shape of the observed emission band, which is consistent with our estimation of the ice particle size from condensation growth and sedimentation timescales. We compared the ice mass mixing ratio with the haze mass mixing ratio inferred in the same region from the continuum emission of CIRS spectra, and derived that the haze mass mixing ratios are ∼30 times larger than the C6H6 ice mass mixing ratios for all observations. Several other unidentified signatures are observed near 687 and 702 ... Article in Journal/Newspaper South pole Wageningen UR (University & Research Centre): Digital Library South Pole Icarus 310 89 104 |
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Open Polar |
collection |
Wageningen UR (University & Research Centre): Digital Library |
op_collection_id |
ftunivwagenin |
language |
English |
topic |
Atmospheres composition structures Infrared observations Titan atmosphere |
spellingShingle |
Atmospheres composition structures Infrared observations Titan atmosphere Vinatier, S. Schmitt, B. Bézard, B. Rannou, P. Dauphin, C. de Kok, R. Jennings, D.E. Flasar, F.M. Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice |
topic_facet |
Atmospheres composition structures Infrared observations Titan atmosphere |
description |
We report the detection of a spectral signature observed at 682 cm−1 by the Cassini Composite Infrared Spectrometer (CIRS) in nadir and limb geometry observations of Titan's southern stratospheric polar region in the middle of southern fall, while stratospheric temperatures are the coldest since the beginning of the Cassini mission. In the same period, many gases observed in CIRS spectra (C2H2, HCN, C4H2, C3H4, HC3N and C6H6) are highly enriched in the stratosphere at high southern latitude due to the air subsidence of the global atmospheric circulation and some of these molecules condense at much higher altitude than usually observed for other latitudes. The 682 cm−1 signature, which is only observed below an altitude of 300 km, is at least partly attributed to the benzene (C6H6) ice ν4 C–H bending mode. While we first observed it in CIRS nadir spectra of the southern polar region in early 2013, we focus here on the study of nadir data acquired in May 2013, which have a more favorable observation geometry. We derived the C6H6 ice mass mixing ratio in 5° latitude bins from the south pole to 65°S and infer the C6H6 cloud top altitude to be located deeper with increasing distance from the pole. We additionally analyzed limb data acquired in March 2015, which were the first limb dataset available after the May 2013 nadir observation, in order to infer a vertical profile of its mass mixing ratio in the 0.1–1 mbar region (250–170 km). We derive an upper limit of ∼1.5 µm for the equivalent radius of pure C6H6 ice particles from the shape of the observed emission band, which is consistent with our estimation of the ice particle size from condensation growth and sedimentation timescales. We compared the ice mass mixing ratio with the haze mass mixing ratio inferred in the same region from the continuum emission of CIRS spectra, and derived that the haze mass mixing ratios are ∼30 times larger than the C6H6 ice mass mixing ratios for all observations. Several other unidentified signatures are observed near 687 and 702 ... |
format |
Article in Journal/Newspaper |
author |
Vinatier, S. Schmitt, B. Bézard, B. Rannou, P. Dauphin, C. de Kok, R. Jennings, D.E. Flasar, F.M. |
author_facet |
Vinatier, S. Schmitt, B. Bézard, B. Rannou, P. Dauphin, C. de Kok, R. Jennings, D.E. Flasar, F.M. |
author_sort |
Vinatier, S. |
title |
Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice |
title_short |
Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice |
title_full |
Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice |
title_fullStr |
Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice |
title_full_unstemmed |
Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS : Detection of benzene ice |
title_sort |
study of titan's fall southern stratospheric polar cloud composition with cassini/cirs : detection of benzene ice |
publishDate |
2018 |
url |
https://research.wur.nl/en/publications/study-of-titans-fall-southern-stratospheric-polar-cloud-compositi https://doi.org/10.1016/j.icarus.2017.12.040 |
geographic |
South Pole |
geographic_facet |
South Pole |
genre |
South pole |
genre_facet |
South pole |
op_source |
Icarus 310 (2018) ISSN: 0019-1035 |
op_relation |
https://edepot.wur.nl/547897 https://research.wur.nl/en/publications/study-of-titans-fall-southern-stratospheric-polar-cloud-compositi doi:10.1016/j.icarus.2017.12.040 |
op_rights |
info:eu-repo/semantics/restrictedAccess Wageningen University & Research |
op_doi |
https://doi.org/10.1016/j.icarus.2017.12.040 |
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Icarus |
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310 |
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89 |
op_container_end_page |
104 |
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1788065592310235136 |