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Nixon CA. The Composition and Chemistry of Titan's Atmosphere. ACS EARTH & SPACE CHEMISTRY 2024; 8:406-456. [PMID: 38533193 PMCID: PMC10961852 DOI: 10.1021/acsearthspacechem.2c00041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 11/02/2023] [Accepted: 02/02/2024] [Indexed: 03/28/2024]
Abstract
In this review I summarize the current state of knowledge about the composition of Titan's atmosphere and our current understanding of the suggested chemistry that leads to that observed composition. I begin with our present knowledge of the atmospheric composition, garnered from a variety of measurements including Cassini-Huygens, the Atacama Large Millimeter/submillimeter Array, and other ground- and space-based telescopes. This review focuses on the typical vertical profiles of gases at low latitudes rather than global and temporal variations. The main body of the review presents a chemical description of how complex molecules are believed to arise from simpler species, considering all known "stable" molecules-those that have been uniquely identified in the neutral atmosphere. The last section of the review is devoted to the gaps in our present knowledge of Titan's chemical composition and how further work may fill those gaps.
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Affiliation(s)
- Conor A. Nixon
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771, United
States
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Blumenthal SD, Mandell AM, Hébrard E, Batalha NE, Cubillos PE, Rugheimer S, Wakeford HR. A COMPARISON OF SIMULATED JWST OBSERVATIONS DERIVED FROM EQUILIBRIUM AND NON-EQUILIBRIUM CHEMISTRY MODELS OF GIANT EXOPLANETS. THE ASTROPHYSICAL JOURNAL 2018; 853:10.3847/1538-4357/aa9e51. [PMID: 31806912 PMCID: PMC6893919 DOI: 10.3847/1538-4357/aa9e51] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We aim to see if the difference between equilibrium and disequilibrium chemistry is observable in the atmospheres of transiting planets by the James Webb Space Telescope (JWST). We perform a case study comparing the dayside emission spectra of three planets like HD 189733b, WASP-80b, and GJ436b, in and out of chemical equilibrium at two metallicities each. These three planets were chosen because they span a large range of planetary masses and equilibrium temperatures, from hot and Jupiter-sized to warm and Neptune-sized. We link the one-dimensional disequilibrium chemistry model from Venot et al. (2012) in which thermochemical kinetics, vertical transport, and photochemistry are taken into account, to the one-dimensional, pseudo line-by-line radiative transfer model, Pyrat Bay, developed especially for hot Jupiters, and then simulate JWST spectra using PandExo for comparing the effects of temperature, metallicity, and radius. We find the most significant differences from 4 to 5 μm due to disequilibrium from CO and CO2 abundances, and also H2O for select cases. Our case study shows a certain "sweet spot" of planetary mass, temperature, and metallicity where the difference between equilibrium and disequilibrium is observable. For a planet similar to WASP-80b, JWST's NIRSpec G395M can detect differences due to disequilibrium chemistry with one eclipse event. For a planet similar to GJ 436b, the observability of differences due to disequilibrium chemistry is possible at low metallicity given five eclipse events, but not possible at the higher metallicity.
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Affiliation(s)
- Sarah D Blumenthal
- NASA Goddard Space Flight Center, Center for Astrobiology, Greenbelt, MD 20771
- University of Maryland Baltimore Country, CRESST
- Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
| | - Avi M Mandell
- NASA Goddard Space Flight Center, Center for Astrobiology, Greenbelt, MD 20771
| | - Eric Hébrard
- NASA Goddard Space Flight Center, Center for Astrobiology, Greenbelt, MD 20771
- Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
| | - Natasha E Batalha
- NASA Goddard Space Flight Center, Center for Astrobiology, Greenbelt, MD 20771
- Department of Astronomy & Astrophysics, Pennsylvania State University, State College, PA 16801
| | - Patricio E Cubillos
- Space Research Institute, Austrian Academy of Sciences, Schmiedlstraße 6, 8042 Graz, Austria
| | - Sarah Rugheimer
- School of Geography & Geosciences, University of St Andrews, St Andrews, United Kingdom
| | - Hannah R Wakeford
- NASA Goddard Space Flight Center, Center for Astrobiology, Greenbelt, MD 20771
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Cui J, Yelle RV, Strobel DF, Müller-Wodarg ICF, Snowden DS, Koskinen TT, Galand M. The CH4structure in Titan's upper atmosphere revisited. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012je004222] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Bell JM, Bougher SW, Waite JH, Ridley AJ, Magee BA, Mandt KE, Westlake J, DeJong AD, Bar–Nun A, Jacovi R, Toth G, De La Haye V. Simulating the one-dimensional structure of Titan's upper atmosphere: 1. Formulation of the Titan Global Ionosphere-Thermosphere Model and benchmark simulations. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010je003636] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Cravens TE, Richard M, Ma YJ, Bertucci C, Luhmann JG, Ledvina S, Robertson IP, Wahlund JE, Ågren K, Cui J, Muller-Wodarg I, Waite JH, Dougherty M, Bell J, Ulusen D. Dynamical and magnetic field time constants for Titan's ionosphere: Empirical estimates and comparisons with Venus. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009ja015050] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - M. Richard
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - Y.-J. Ma
- Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
| | - C. Bertucci
- Instituto de Astronomía y Física del Espacio; Buenos Aires Argentina
| | - J. G. Luhmann
- Space Sciences Laboratory; University of California; Berkeley California USA
| | - S. Ledvina
- Space Sciences Laboratory; University of California; Berkeley California USA
| | - I. P. Robertson
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | | | - K. Ågren
- Swedish Institute of Space Physics; Uppsala Sweden
| | - J. Cui
- Space and Atmospheric Physics Group, Blackett Laboratory; Imperial College London; London UK
| | - I. Muller-Wodarg
- Space and Atmospheric Physics Group, Blackett Laboratory; Imperial College London; London UK
| | - J. H. Waite
- Southwest Research Institute; San Antonio Texas USA
| | - M. Dougherty
- Space and Atmospheric Physics Group, Blackett Laboratory; Imperial College London; London UK
| | - J. Bell
- Southwest Research Institute; San Antonio Texas USA
| | - D. Ulusen
- Space Sciences Laboratory; University of California; Berkeley California USA
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Galand M, Yelle R, Cui J, Wahlund JE, Vuitton V, Wellbrock A, Coates A. Ionization sources in Titan's deep ionosphere. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009ja015100] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Marina Galand
- Department of Physics; Imperial College London; London UK
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Roger Yelle
- Lunar and Planetary Laboratory; University of Arizona; Tucson Arizona USA
| | - Jun Cui
- Department of Physics; Imperial College London; London UK
| | | | - Véronique Vuitton
- Laboratoire de Planétologie de Grenoble; Université Joseph Fourier; Grenoble France
| | - Anne Wellbrock
- Mullard Space Science Laboratory; University College London; Surrey UK
| | - Andrew Coates
- Mullard Space Science Laboratory; University College London; Surrey UK
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Cui J, Galand M, Yelle RV, Wahlund JE, Ågren K, Waite JH, Dougherty MK. Ion transport in Titan's upper atmosphere. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009ja014563] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- J. Cui
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
| | - M. Galand
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
| | - R. V. Yelle
- Lunar and Planetary Laboratory; University of Arizona; Tucson Arizona USA
| | | | - K. Ågren
- Swedish Institute of Space Physics; Uppsala Sweden
| | - J. H. Waite
- Southwest Research Institute; San Antonio Texas USA
| | - M. K. Dougherty
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
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Cui J, Galand M, Yelle RV, Vuitton V, Wahlund JE, Lavvas PP, Müller-Wodarg ICF, Cravens TE, Kasprzak WT, Waite JH. Diurnal variations of Titan's ionosphere. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2009ja014228] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- J. Cui
- Space and Atmospheric Physics Group, Department of Physics; Imperial College; London UK
| | - M. Galand
- Space and Atmospheric Physics Group, Department of Physics; Imperial College; London UK
| | - R. V. Yelle
- Lunar and Planetary Laboratory; University of Arizona; Tucson Arizona USA
| | - V. Vuitton
- Laboratoire de Planétologie de Grenoble; Université Joseph Fourier/CNRS; Grenoble France
| | - J.-E. Wahlund
- Uppsala Division; Swedish Institute of Space Physics; Uppsala Sweden
| | - P. P. Lavvas
- Lunar and Planetary Laboratory; University of Arizona; Tucson Arizona USA
| | | | - T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - W. T. Kasprzak
- Solar System Exploration Division; NASA Goddard Space Flight Center; Greenbelt Maryland USA
| | - J. H. Waite
- Space Science and Engineering Division; Southwest Research Institute; San Antonio Texas USA
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De La Haye V, Waite JH, Cravens TE, Bougher SW, Robertson IP, Bell JM. Heating Titan's upper atmosphere. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008ja013078] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - J. H. Waite
- Southwest Research Institute; San Antonio Texas USA
| | - T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - S. W. Bougher
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - I. P. Robertson
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - J. M. Bell
- Southwest Research Institute; San Antonio Texas USA
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Müller-Wodarg ICF, Yelle RV, Cui J, Waite JH. Horizontal structures and dynamics of Titan's thermosphere. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je003033] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Müller-Wodarg ICF, Yelle RV, Borggren N, Waite JH. Waves and horizontal structures in Titan's thermosphere. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006ja011961] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Müller-Wodarg ICF. On the global distribution of neutral gases in Titan's upper atmosphere and its effect on the thermal structure. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2003ja010054] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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