Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA
Titan, Saturn’s largest satellite, maintains an atmosphere composed primarily of nitrogen (N _2 ) and methane (CH _4 ) that leads to complex organic chemistry. Some of the nitriles (CN-bearing organics) on Titan are known to have substantially enhanced ^15 N abundances compared to Earth and Titan’s...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/PSJ/adc390 |
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| author | Jonathon Nosowitz Martin A. Cordiner Conor A. Nixon Alexander E. Thelen Zbigniew Kisiel Nicholas A. Teanby Patrick G. J. Irwin Steven B. Charnley Véronique Vuitton |
| author_facet | Jonathon Nosowitz Martin A. Cordiner Conor A. Nixon Alexander E. Thelen Zbigniew Kisiel Nicholas A. Teanby Patrick G. J. Irwin Steven B. Charnley Véronique Vuitton |
| author_sort | Jonathon Nosowitz |
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| description | Titan, Saturn’s largest satellite, maintains an atmosphere composed primarily of nitrogen (N _2 ) and methane (CH _4 ) that leads to complex organic chemistry. Some of the nitriles (CN-bearing organics) on Titan are known to have substantially enhanced ^15 N abundances compared to Earth and Titan’s dominant nitrogen (N _2 ) reservoir. The ^14 N/ ^15 N isotopic ratio in Titan’s nitriles can provide better constraints on the synthesis of nitrogen-bearing organics in planetary atmospheres as well as insights into the origin of Titan’s large nitrogen abundance. Using high signal-to-noise ratio (>13), disk-integrated observations obtained with the Atacama Large Millimeter/submillimeter Array Band 6 receiver (211–275 GHz), we measure the ^14 N/ ^15 N and ^12 C/ ^13 C isotopic ratios of acetonitrile (CH _3 CN) in Titan’s stratosphere. Using the NEMESIS, we derived the CH _3 CN/ ^13 CH _3 CN ratio to be 89.2 ± 7.0 and the CH _3 CN/CH _3 ^13 CN ratio to be 91.2 ± 6.0, in agreement with the ^12 C/ ^13 C ratio in Titan’s methane and other solar system species. We found the ^14 N/ ^15 N isotopic ratio to be 68.9 ± 4.2, consistent with previously derived values for HCN and HC _3 N, confirming an enhanced ^15 N abundance in Titan’s nitriles compared with the bulk atmospheric N _2 value of ^14 N/ ^15 N = 168, in agreement with chemical models incorporating isotope-selective photodissociation of N _2 at high altitudes. |
| format | Article |
| id | doaj-art-0c819e3107364e5ea88dca2acee84ca9 |
| institution | OA Journals |
| issn | 2632-3338 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Planetary Science Journal |
| spelling | doaj-art-0c819e3107364e5ea88dca2acee84ca92025-08-20T01:48:29ZengIOP PublishingThe Planetary Science Journal2632-33382025-01-016510710.3847/PSJ/adc390Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMAJonathon Nosowitz0https://orcid.org/0009-0004-1366-9472Martin A. Cordiner1https://orcid.org/0000-0001-8233-2436Conor A. Nixon2https://orcid.org/0000-0001-9540-9121Alexander E. Thelen3https://orcid.org/0000-0002-8178-1042Zbigniew Kisiel4https://orcid.org/0000-0002-2570-3154Nicholas A. Teanby5https://orcid.org/0000-0003-3108-5775Patrick G. J. Irwin6https://orcid.org/0000-0002-6772-384XSteven B. Charnley7https://orcid.org/0000-0001-6752-5109Véronique Vuitton8https://orcid.org/0000-0001-7273-1898Department of Physics, The Catholic University of America , Washington, DC 20064, USA ; nosowitz@cua.edu; Solar System Exploration Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USADepartment of Physics, The Catholic University of America , Washington, DC 20064, USA ; nosowitz@cua.edu; Solar System Exploration Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USASolar System Exploration Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USADivision of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125, USAInstitute of Physics , Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa, PolandSchool of Earth Sciences, University of Bristol , Bristol BS8 1RJ, UKAtmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford , Oxford OX1 3PU, UKSolar System Exploration Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USAUniv. Grenoble Alpes , CNRS, IPAG, 38000 Grenoble, FranceTitan, Saturn’s largest satellite, maintains an atmosphere composed primarily of nitrogen (N _2 ) and methane (CH _4 ) that leads to complex organic chemistry. Some of the nitriles (CN-bearing organics) on Titan are known to have substantially enhanced ^15 N abundances compared to Earth and Titan’s dominant nitrogen (N _2 ) reservoir. The ^14 N/ ^15 N isotopic ratio in Titan’s nitriles can provide better constraints on the synthesis of nitrogen-bearing organics in planetary atmospheres as well as insights into the origin of Titan’s large nitrogen abundance. Using high signal-to-noise ratio (>13), disk-integrated observations obtained with the Atacama Large Millimeter/submillimeter Array Band 6 receiver (211–275 GHz), we measure the ^14 N/ ^15 N and ^12 C/ ^13 C isotopic ratios of acetonitrile (CH _3 CN) in Titan’s stratosphere. Using the NEMESIS, we derived the CH _3 CN/ ^13 CH _3 CN ratio to be 89.2 ± 7.0 and the CH _3 CN/CH _3 ^13 CN ratio to be 91.2 ± 6.0, in agreement with the ^12 C/ ^13 C ratio in Titan’s methane and other solar system species. We found the ^14 N/ ^15 N isotopic ratio to be 68.9 ± 4.2, consistent with previously derived values for HCN and HC _3 N, confirming an enhanced ^15 N abundance in Titan’s nitriles compared with the bulk atmospheric N _2 value of ^14 N/ ^15 N = 168, in agreement with chemical models incorporating isotope-selective photodissociation of N _2 at high altitudes.https://doi.org/10.3847/PSJ/adc390TitanRemote sensingRadio interferometrySubmillimeter astronomy |
| spellingShingle | Jonathon Nosowitz Martin A. Cordiner Conor A. Nixon Alexander E. Thelen Zbigniew Kisiel Nicholas A. Teanby Patrick G. J. Irwin Steven B. Charnley Véronique Vuitton Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA The Planetary Science Journal Titan Remote sensing Radio interferometry Submillimeter astronomy |
| title | Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA |
| title_full | Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA |
| title_fullStr | Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA |
| title_full_unstemmed | Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA |
| title_short | Improved Carbon and Nitrogen Isotopic Ratios for CH3CN in Titan’s Atmosphere Using ALMA |
| title_sort | improved carbon and nitrogen isotopic ratios for ch3cn in titan s atmosphere using alma |
| topic | Titan Remote sensing Radio interferometry Submillimeter astronomy |
| url | https://doi.org/10.3847/PSJ/adc390 |
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