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Konatham S, Martin-Torres J, Zorzano MP. Atmospheric composition of exoplanets based on the thermal escape of gases and implications for habitability. Proc Math Phys Eng Sci 2020; 476:20200148. [PMID: 33061789 PMCID: PMC7544335 DOI: 10.1098/rspa.2020.0148] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 07/16/2020] [Indexed: 12/17/2022] Open
Abstract
The detection of habitable exoplanets is an exciting scientific and technical challenge. Owing to the current and most likely long-lasting impossibility of performing in situ exploration of exoplanets, their study and hypotheses regarding their capability to host life will be based on the restricted low-resolution spatial and spectral information of their atmospheres. On the other hand, with the advent of the upcoming exoplanet survey missions and technological improvements, there is a need for preliminary discrimination that can prioritize potential candidates within the fast-growing list of exoplanets. Here we estimate, for the first time and using the kinetic theory of gases, a list of the possible atmospheric species that can be retained in the atmospheres of the known exoplanets. We conclude that, based on our current knowledge of the detected exoplanets, 45 of them are good candidates for habitability studies. These exoplanets could have Earth-like atmospheres and should be able to maintain stable liquid water. Our results suggest that the current definition of a habitable zone around a star should be revisited and that the capacity of the planet to host an Earth-like atmosphere to support the stability of liquid water should be added.
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Affiliation(s)
- Samuel Konatham
- Group of Atmospheric Science, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Luleå, Sweden
| | - Javier Martin-Torres
- Group of Atmospheric Science, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Luleå, Sweden.,Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada, Spain.,School of Geosciences, University of Aberdeen, Meston Building, King's College, Aberdeen, UK
| | - Maria-Paz Zorzano
- Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain.,Group of Atmospheric Science, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Luleå, Sweden
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Sanches-Neto FO, Coutinho ND, Palazzetti F, Carvalho-Silva VH. Temperature dependence of rate constants for the H(D) + CH4 reaction in gas and aqueous phase: deformed Transition-State Theory study including quantum tunneling and diffusion effects. Struct Chem 2019. [DOI: 10.1007/s11224-019-01437-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Tanis E. Reactive scattering of an electronically-excited nitrogen atom with H 2 and its isotopic variants: N(2D)+H2/D2/T2. COMPUT THEOR CHEM 2016. [DOI: 10.1016/j.comptc.2016.02.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Li C, Zhang X, Gao P, Yung Y. VERTICAL DISTRIBUTION OF
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-HYDROCARBONS IN THE STRATOSPHERE OF TITAN. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/2041-8205/803/2/l19] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Peng Z, Carrasco N, Pernot P. Modeling of synchrotron-based laboratory simulations of Titan’s ionospheric photochemistry. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.grj.2014.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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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, Gell D, Fletcher G. Simulating the one-dimensional structure of Titan's upper atmosphere: 3. Mechanisms determining methane escape. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010je003639] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
The Cassini-Huygens mission discovered an active "hydrologic cycle" on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogen-methane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU--a far more stable environment than the approximately 0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.
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Affiliation(s)
- Jonathan I Lunine
- Dipartimento di Fisica, University of Rome "Tor Vergata", Rome, Italy 00133.
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Yelle RV, Vuitton V, Lavvas P, Klippenstein SJ, Smith MA, Hörst SM, Cui J. Formation of NH3 and CH2NH in Titan's upper atmosphere. Faraday Discuss 2011; 147:31-49; discussion 83-102. [PMID: 21302541 DOI: 10.1039/c004787m] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The large abundance of NH3 in Titan's upper atmosphere is a consequence of coupled ion and neutral chemistry. The density of NH3 is inferred from the measured abundance of NH4+. NH3 is produced primarily through reaction of NH2 with H2CN, a process neglected in previous models. NH2 is produced by several reactions including electron recombination of CH2NH2+. The density of CH2NH2+ is closely linked to the density of CH2NH through proton exchange reactions and recombination. CH2NH is produced by reaction of N(2D) and NH with ambient hydrocarbons. Thus, production of NH3 is the result of a chain of reactions involving non-nitrile functional groups and the large density of NH3 implies large densities for these associated molecules. This suggests that amine and imine functional groups may be incorporated as well in other, more complex organic molecules.
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Affiliation(s)
- Roger V Yelle
- Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA
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Bell JM, Bougher SW, Waite JH, Ridley AJ, Magee BA, Mandt KE, Westlake J, DeJong AD, De La Haye V, Bar-Nun A, Jacovi R, Toth G, Gell D, Fletcher G. Simulating the one-dimensional structure of Titan's upper atmosphere: 2. Alternative scenarios for methane escape. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010je003638] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Niemann HB, Atreya SK, Demick JE, Gautier D, Haberman JA, Harpold DN, Kasprzak WT, Lunine JI, Owen TC, Raulin F. Composition of Titan's lower atmosphere and simple surface volatiles as measured by the Cassini-Huygens probe gas chromatograph mass spectrometer experiment. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010je003659] [Citation(s) in RCA: 334] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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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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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Johnson RE. Sputtering and heating of Titan's upper atmosphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:753-771. [PMID: 19073463 DOI: 10.1098/rsta.2008.0244] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Titan is an important endpoint for understanding atmospheric evolution. Prior to Cassini's arrival at Saturn, modelling based on Voyager data indicated that the hydrogen escape rate was large (1-3x1028amus-1), but the escape rates for carbon and nitrogen species were relatively small (5x1026amus-1) and dominated by atmospheric sputtering. Recent analysis of the structure of Titan's thermosphere and corona attained from the Ion and Neutral Mass Spectrometer and the Huygens Atmospheric Structure Instrument on Cassini have led to substantially larger estimates of the loss rate for heavy species (0.3-5x1028amus-1). At the largest rate suggested, a mass that is a significant fraction of the present atmosphere would have been lost to space in 4Gyr; hence, understanding the nature of the processes driving escape is critical. The recent estimates of neutral escape are reviewed here, with particular emphasis on plasma-induced sputtering and heating. Whereas the loss of hydrogen is clearly indicated by the altitude dependence of the H2 density, three different one-dimensional models were used to estimate the heavy-molecule loss rate using the Cassini data for atmospheric density versus altitude. The solar heating rate and the nitrogen density profile versus altitude were used in a fluid dynamic model to extract an average net upward flux below the exobase; the diffusion of methane through nitrogen was described below the exobase using a model that allowed for outward flow; and the coronal structure above the exobase was simulated by presuming that the observed atmospheric structure was due to solar- and plasma-induced hot particle production. In the latter, it was hypothesized that hot recoils from photochemistry or plasma-ion-induced heating were required. In the other two models, the upward flow extracted is driven by heat conduction from below, which is assumed to continue to act above the nominal exobase, producing a process referred to as 'slow hydrodynamic' escape. These models and the resulting loss rates are reviewed and compared. It is pointed out that preliminary estimates of the composition of the magnetospheric plasma at Titan's orbit appear to be inconsistent with the largest loss rates suggested for the heavy species, and the mean upward flow extracted in the one-dimensional models could be consistent with atmospheric loss by other mechanisms or with transport to other regions of Titan's atmosphere.
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Affiliation(s)
- Robert E Johnson
- University of Virginia, Charlottesville, VA 22904, USA Department of Physics, New York University, New York, NY 10003, 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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Cui J, Yelle RV, Volk K. Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je003032] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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