Observations of Titan's Stratosphere During Northern Summer: Temperatures, CH3CN and CH3D Abundances
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| Autores principales: | , , , , , , , , , , , , , |
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| Formato: | Preprint |
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2024
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| author | Thelen, Alexander E. Nixon, Conor A. Cordiner, Martin A. Lellouch, Emmanuel Vinatier, Sandrine Teanby, Nicholas A. Butler, Bryan Charnley, Steven B. Cosentino, Richard G. de Kleer, Katherine Irwin, Patrick G. J. Gurwell, Mark A. Kisiel, Zbigniew Moreno, Raphael |
| author_facet | Thelen, Alexander E. Nixon, Conor A. Cordiner, Martin A. Lellouch, Emmanuel Vinatier, Sandrine Teanby, Nicholas A. Butler, Bryan Charnley, Steven B. Cosentino, Richard G. de Kleer, Katherine Irwin, Patrick G. J. Gurwell, Mark A. Kisiel, Zbigniew Moreno, Raphael |
| contents | Titan's atmospheric composition and dynamical state have previously been studied over numerous epochs by both ground- and space-based facilities. However, stratospheric measurements remain sparse during Titan's northern summer and fall. The lack of seasonal symmetry in observations of Titan's temperature field and chemical abundances raises questions about the nature of the middle atmosphere's meridional circulation and evolution over Titan's 29-yr seasonal cycle that can only be answered through long-term monitoring campaigns. Here, we present maps of Titan's stratospheric temperature, acetonitrile (or methyl cyanide; CH$_3$CN), and monodeuterated methane (CH$_3$D) abundances following Titan's northern summer solstice obtained with Band 9 ($\sim0.43$ mm) ALMA observations. We find that increasing temperatures towards high-southern latitudes, currently in winter, resemble those observed during Titan's northern winter by the Cassini mission. Acetonitrile abundances have changed significantly since previous (sub)millimeter observations, and we find that the species is now highly concentrated at high-southern latitudes. The stratospheric CH$_3$D content is found to range between 4-8 ppm in these observations, and we infer the CH$_4$ abundance to vary between $\sim0.9-1.6\%$ through conversion with previously measured D/H values. A global value of CH$_4=1.15\%$ was retrieved, lending further evidence to the temporal and spatial variability of Titan's stratospheric methane when compared with previous measurements. Additional observations are required to determine the cause and magnitude of stratospheric enhancements in methane during these poorly understood seasons on Titan. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2405_02535 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Observations of Titan's Stratosphere During Northern Summer: Temperatures, CH3CN and CH3D Abundances Thelen, Alexander E. Nixon, Conor A. Cordiner, Martin A. Lellouch, Emmanuel Vinatier, Sandrine Teanby, Nicholas A. Butler, Bryan Charnley, Steven B. Cosentino, Richard G. de Kleer, Katherine Irwin, Patrick G. J. Gurwell, Mark A. Kisiel, Zbigniew Moreno, Raphael Earth and Planetary Astrophysics Titan's atmospheric composition and dynamical state have previously been studied over numerous epochs by both ground- and space-based facilities. However, stratospheric measurements remain sparse during Titan's northern summer and fall. The lack of seasonal symmetry in observations of Titan's temperature field and chemical abundances raises questions about the nature of the middle atmosphere's meridional circulation and evolution over Titan's 29-yr seasonal cycle that can only be answered through long-term monitoring campaigns. Here, we present maps of Titan's stratospheric temperature, acetonitrile (or methyl cyanide; CH$_3$CN), and monodeuterated methane (CH$_3$D) abundances following Titan's northern summer solstice obtained with Band 9 ($\sim0.43$ mm) ALMA observations. We find that increasing temperatures towards high-southern latitudes, currently in winter, resemble those observed during Titan's northern winter by the Cassini mission. Acetonitrile abundances have changed significantly since previous (sub)millimeter observations, and we find that the species is now highly concentrated at high-southern latitudes. The stratospheric CH$_3$D content is found to range between 4-8 ppm in these observations, and we infer the CH$_4$ abundance to vary between $\sim0.9-1.6\%$ through conversion with previously measured D/H values. A global value of CH$_4=1.15\%$ was retrieved, lending further evidence to the temporal and spatial variability of Titan's stratospheric methane when compared with previous measurements. Additional observations are required to determine the cause and magnitude of stratospheric enhancements in methane during these poorly understood seasons on Titan. |
| title | Observations of Titan's Stratosphere During Northern Summer: Temperatures, CH3CN and CH3D Abundances |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2405.02535 |