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Cordiner M, Thelen A, Cavalie T, Cosentino R, Fletcher LN, Gurwell M, de Kleer K, Kuan YJ, Lellouch E, Moullet A, Nixon C, de Pater I, Teanby N, Butler B, Charnley S, Milam S, Moreno R, Booth M, Klaassen P, Cicone C, Mroczkowski T, Di Mascolo L, Johnstone D, van Kampen E, Lee M, Liu D, Maccarone T, Saintonge A, Smith M, Wedemeyer S. Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Planetary and cometary atmospheres. OPEN RESEARCH EUROPE 2024; 4:78. [PMID: 39100074 PMCID: PMC11297396 DOI: 10.12688/openreseurope.17473.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 03/25/2024] [Indexed: 08/06/2024]
Abstract
The study of planets and small bodies within our Solar System is fundamental for understanding the formation and evolution of the Earth and other planets. Compositional and meteorological studies of the giant planets provide a foundation for understanding the nature of the most commonly observed exoplanets, while spectroscopic observations of the atmospheres of terrestrial planets, moons, and comets provide insights into the past and present-day habitability of planetary environments, and the availability of the chemical ingredients for life. While prior and existing (sub)millimeter observations have led to major advances in these areas, progress is hindered by limitations in the dynamic range, spatial and temporal coverage, as well as sensitivity of existing telescopes and interferometers. Here, we summarize some of the key planetary science use cases that factor into the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50-m class single dish facility: (1) to more fully characterize planetary wind fields and atmospheric thermal structures, (2) to measure the compositions of icy moon atmospheres and plumes, (3) to obtain detections of new, astrobiologically relevant gases and perform isotopic surveys of comets, and (4) to perform synergistic, temporally-resolved measurements in support of dedicated interplanetary space missions. The improved spatial coverage (several arcminutes), resolution (~ 1.2'' - 12''), bandwidth (several tens of GHz), dynamic range (~ 10 5) and sensitivity (~ 1 mK km s -1) required by these science cases would enable new insights into the chemistry and physics of planetary environments, the origins of prebiotic molecules and the habitability of planetary systems in general.
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Affiliation(s)
- Martin Cordiner
- Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, 20771-0003, USA
- Department of Physics, Catholic University of America, Washington, DC, 20064, USA
| | - Alexander Thelen
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125, USA
| | - Thibault Cavalie
- Laboratoire d’Astrophysique de Bordeaux, Universite de Bordeaux, Geoffroy Saint-Hilaire, Nouvelle-Aquitaine, 33615, France
- LESIA, Observatoire de Paris, PSL Research University, Sorbonne Universite, Meudon, 92195, France
| | | | - Leigh N. Fletcher
- School of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
| | - Mark Gurwell
- Center for Astrophysics, Harvard Smithsonian, Cambridge, MA, 02138, USA
| | - Katherine de Kleer
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125, USA
| | - Yi-Jehng Kuan
- National Taiwan Normal University, Taipei City, 116, Taiwan
| | - Emmanuel Lellouch
- LESIA, Observatoire de Paris, PSL Research University, Sorbonne Universite, Meudon, 92195, France
| | - Arielle Moullet
- National Radio Astronomy Observatory, Charlottesville, VA, 22903, USA
| | - Conor Nixon
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - Imke de Pater
- Departments of Astronomy and of Earth and Planetary Science, University of California Berkeley, Berkeley, California, 94720, USA
| | - Nicholas Teanby
- School of Earth Sciences, University of Bristol, Bristol, England, BS8 1RJ, UK
| | - Bryan Butler
- National Radio Astronomy Observatory, Socorro, NM, 87801, USA
| | - Steven Charnley
- Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, 20771-0003, USA
| | - Stefanie Milam
- Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, 20771-0003, USA
| | - Raphael Moreno
- LESIA, Observatoire de Paris, PSL Research University, Sorbonne Universite, Meudon, 92195, France
| | - Mark Booth
- UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK
| | - Pamela Klaassen
- UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK
| | - Claudia Cicone
- Institute of Theoretical Astrophysics, University of Oslo, Oslo, 0315, Norway
| | | | - Luca Di Mascolo
- Laboratoire Lagrange, Universite Cote d'Azur, Nice, Provence-Alpes-Côte d'Azur, 06304, France
- INAF – Osservatorio Astronomico di Trieste, Trieste, 34131, Italy
- IFPU – Institute for Fundamental Physics of the Univers, Trieste, 34014, Italy
- Astronomy Unit, Department of Physics, University of Trieste, Trieste, 34131, Italy
| | - Doug Johnstone
- NRC Herzberg Astronomy and Astrophysics Research Centre, Victoria, BC, V9E 2E7, Canada
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 5C, Canada
| | | | - Minju Lee
- Cosmic Dawn Center, København, Denmark
| | - Daizhong Liu
- Max Planck Institute for Extraterrestrial Physics, Garching bei München, Bayern, D-85748, Germany
- Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Thomas Maccarone
- Department of Physics & Astronomy, Texas Tech University, Lubbock, Texas, 79409-1051, USA
| | - Amelie Saintonge
- Max Planck Institute for Extraterrestrial Physics, Garching bei München, Bayern, D-85748, Germany
- Department of Physics and Astronomy, University College London, London, England, WC1E 6BT, UK
| | - Matthew Smith
- School of Physics & Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK
| | - Sven Wedemeyer
- Rosseland Centre for Solar Physics, University of Oslo, Oslo, N-0315, Norway
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Fletcher LN, Cavalié T, Grassi D, Hueso R, Lara LM, Kaspi Y, Galanti E, Greathouse TK, Molyneux PM, Galand M, Vallat C, Witasse O, Lorente R, Hartogh P, Poulet F, Langevin Y, Palumbo P, Gladstone GR, Retherford KD, Dougherty MK, Wahlund JE, Barabash S, Iess L, Bruzzone L, Hussmann H, Gurvits LI, Santolik O, Kolmasova I, Fischer G, Müller-Wodarg I, Piccioni G, Fouchet T, Gérard JC, Sánchez-Lavega A, Irwin PGJ, Grodent D, Altieri F, Mura A, Drossart P, Kammer J, Giles R, Cazaux S, Jones G, Smirnova M, Lellouch E, Medvedev AS, Moreno R, Rezac L, Coustenis A, Costa M. Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer. SPACE SCIENCE REVIEWS 2023; 219:53. [PMID: 37744214 PMCID: PMC10511624 DOI: 10.1007/s11214-023-00996-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 08/10/2023] [Indexed: 09/26/2023]
Abstract
ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 μm), and sub-millimetre sounding (near 530-625 GHz and 1067-1275 GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet.
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Affiliation(s)
- Leigh N. Fletcher
- School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Thibault Cavalié
- Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
- LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS, 5 place Jules Janssen, 92195 Meudon, France
| | - Davide Grassi
- Istituto di Astrofisica e Planetologia Spaziali - Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere, 100, I-00133 Roma, Italy
| | - Ricardo Hueso
- Física Aplicada, Escuela de Ingeniería de Bilbao Universidad del País Vasco UPV/EHU, Plaza Ingeniero Torres Quevedo, 1, 48013 Bilbao, Spain
| | - Luisa M. Lara
- Instituto de Astrofísica de Andalucía-CSIC, c/Glorieta de la Astronomía 3, 18008 Granada, Spain
| | - Yohai Kaspi
- Dept. of Earth and Planetray Science, Weizmann Institute of Science, Rehovot, Israel 76100
| | - Eli Galanti
- Dept. of Earth and Planetray Science, Weizmann Institute of Science, Rehovot, Israel 76100
| | | | | | - Marina Galand
- Department of Physics, Imperial College London, Prince Consort Road, London, SW7 2AZ UK
| | - Claire Vallat
- European Space Agency (ESA), ESAC Camino Bajo del Castillo s/n Villafranca del Castillo, 28692 Villanueva de la Cañada (Madrid), Spain
| | - Olivier Witasse
- European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Noordwijk, Netherlands
| | - Rosario Lorente
- European Space Agency (ESA), ESAC Camino Bajo del Castillo s/n Villafranca del Castillo, 28692 Villanueva de la Cañada (Madrid), Spain
| | - Paul Hartogh
- Max-Planck-Institut für Sonnensystemforschung, 37077 Göttingen, Germany
| | - François Poulet
- Institut d’Astrophysique Spatiale, CNRS/Université Paris-Sud, 91405 Orsay Cedex, France
| | - Yves Langevin
- Institut d’Astrophysique Spatiale, CNRS/Université Paris-Sud, 91405 Orsay Cedex, France
| | - Pasquale Palumbo
- Istituto di Astrofisica e Planetologia Spaziali - Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere, 100, I-00133 Roma, Italy
| | - G. Randall Gladstone
- Southwest Research Institute, San Antonio, TX 78228 United States
- University of Texas at San Antonio, San Antonio, TX United States
| | - Kurt D. Retherford
- Southwest Research Institute, San Antonio, TX 78228 United States
- University of Texas at San Antonio, San Antonio, TX United States
| | | | | | - Stas Barabash
- Swedish Institute of Space Physics (IRF), Kiruna, Sweden
| | - Luciano Iess
- Dipartimento di ingegneria meccanica e aerospaziale, Universit á La Sapienza, Roma, Italy
| | - Lorenzo Bruzzone
- Department of Information Engineering and Computer Science, Remote Sensing Laboratory, University of Trento, Via Sommarive 14, Trento, I-38123 Italy
| | - Hauke Hussmann
- Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany
| | - Leonid I. Gurvits
- Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
- Aerospace Faculty, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
| | - Ondřej Santolik
- Department of Space Physics, Institute of Atmospheric Physics of the Czech Academy of Sciences, Prague, Czechia
- Faculty of Mathematics and Physics, Charles University, Prague, Czechia
| | - Ivana Kolmasova
- Department of Space Physics, Institute of Atmospheric Physics of the Czech Academy of Sciences, Prague, Czechia
- Faculty of Mathematics and Physics, Charles University, Prague, Czechia
| | - Georg Fischer
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
| | | | - Giuseppe Piccioni
- Istituto di Astrofisica e Planetologia Spaziali - Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere, 100, I-00133 Roma, Italy
| | - Thierry Fouchet
- LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS, 5 place Jules Janssen, 92195 Meudon, France
| | | | - Agustin Sánchez-Lavega
- Física Aplicada, Escuela de Ingeniería de Bilbao Universidad del País Vasco UPV/EHU, Plaza Ingeniero Torres Quevedo, 1, 48013 Bilbao, Spain
| | - Patrick G. J. Irwin
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Parks Rd, Oxford, OX1 3PU UK
| | - Denis Grodent
- LPAP, STAR Institute, Université de Liège, Liège, Belgium
| | - Francesca Altieri
- Istituto di Astrofisica e Planetologia Spaziali - Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere, 100, I-00133 Roma, Italy
| | - Alessandro Mura
- Istituto di Astrofisica e Planetologia Spaziali - Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere, 100, I-00133 Roma, Italy
| | - Pierre Drossart
- LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS, 5 place Jules Janssen, 92195 Meudon, France
- Institut d’Astrophysique de Paris, CNRS, Sorbonne Université, 98bis Boulevard Arago, 75014 Paris, France
| | - Josh Kammer
- Southwest Research Institute, San Antonio, TX 78228 United States
| | - Rohini Giles
- Southwest Research Institute, San Antonio, TX 78228 United States
| | - Stéphanie Cazaux
- Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
| | - Geraint Jones
- UCL Mullard Space Science Laboratory, Hombury St. Mary, Dorking, RH5 6NT UK
- The Centre for Planetary Sciences at UCL/Birkbeck, London, WC1E 6BT UK
| | - Maria Smirnova
- Dept. of Earth and Planetray Science, Weizmann Institute of Science, Rehovot, Israel 76100
| | - Emmanuel Lellouch
- LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS, 5 place Jules Janssen, 92195 Meudon, France
| | | | - Raphael Moreno
- LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS, 5 place Jules Janssen, 92195 Meudon, France
| | - Ladislav Rezac
- Max-Planck-Institut für Sonnensystemforschung, 37077 Göttingen, Germany
| | - Athena Coustenis
- LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS, 5 place Jules Janssen, 92195 Meudon, France
| | - Marc Costa
- Rhea Group, for European Space Agency, ESAC, Madrid, Spain
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Inclusion of Electron Interactions by Rate Equations in Chemical Models. ATOMS 2022. [DOI: 10.3390/atoms10020062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/10/2022] Open
Abstract
The concept of treating subranges of the electron energy spectrum as species in chemical models is investigated. This is intended to facilitate simple modification of chemical models by incorporating the electron interactions as additional rate equations. It is anticipated that this embedding of fine details of the energy dependence of the electron interactions into rate equations will yield an improvement in computational efficiency compared to other methods. It will be applicable in situations where the electron density is low enough that the electron interactions with chemical species are significant compared to electron–electron interactions. A target application is the simulation of electron processes in the D-region of the Earth’s atmosphere, but it is anticipated that the method would be useful in other areas, including enhancement of Monte Carlo simulation of electron–liquid interactions and simulations of chemical reactions and radical generation induced by electrons and positrons in biomolecular systems. The aim here is to investigate the accuracy and practicality of the method. In particular, energy must be conserved, while the number of subranges should be small to reduce computation time and their distribution should be logarithmic in order to represent processes over a wide range of electron energies. The method is applied here to the interaction by inelastic and superelastic collisions of electrons with a gas of molecules with only one excited vibrational level. While this is unphysical, it allows the method to be validated by checking for accuracy, energy conservation, maintenance of equilibrium and evolution of a Maxwellian electron spectrum.
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Adams D, Luo Y, Wong ML, Dunn P, Christensen M, Dong C, Hu R, Yung Y. Nitrogen Fixation at Early Mars. ASTROBIOLOGY 2021; 21:968-980. [PMID: 34339294 DOI: 10.1089/ast.2020.2273] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The Mars Science Laboratory (MSL) recently discovered nitrates in Gale Crater (e.g., Stern et al., 2015; Sutter et al., 2017). One possible mechanism for ancient nitrate deposition on Mars is through HNOx formation and rain out in the atmosphere, for which lightning-induced NO is likely the fundamental source. This study investigates nitrogen (N2) fixation in early Mars' atmosphere, with implications for early Mars' habitability. We consider a 1 bar atmosphere of background CO2, with abundance of N2, hydrogen, and methane varied from 1% to 10% to explore a swath of potential early Mars climates. We derive lightning-induced thermochemical equilibrium fluxes of NO and HCN by coupling the lightning-rate parametrization from the study of Romps et al. (2014) with chemical equilibrium with applications, and we use a Geant4 simulation platform to estimate the effect of solar energetic particle events. These fluxes are used as input into KINETICS, the Caltech/JPL coupled photochemistry and transport code, which models the chemistry of 50 species linked by 495 reactions to derive rain-out fluxes of HNOx and HCN. We compute equilibrium concentrations of cyanide and nitrate in a putative northern ocean at early Mars, assuming hydrothermal vent circulation and photoreduction act as the dominant loss mechanisms. We find average oceanic concentrations of ∼0.1-2 nM nitrate and ∼0.01-2 mM cyanide. HCN is critical for protein synthesis at concentrations >0.01 M (e.g., Holm and Neubeck, 2009), and our result is astrobiologically significant if secondary local concentration mechanisms occurred. Nitrates may act as high-potential electron acceptors for early metabolisms, although the minimum concentration required is unknown. Our study derives concentrations that will be useful for future laboratory studies to investigate the habitability at early Mars. The aqueous nitrate concentrations correspond to surface nitrate precipitates of ∼1-8 × 10-4 wt % that may have formed after the evaporation of surface waters, and these values roughly agree with recent MSL measurements.
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Affiliation(s)
- Danica Adams
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
| | - Yangcheng Luo
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
| | - Michael L Wong
- Department of Astronomy and Astrobiology Program, University of Washington, Seattle, Washington, USA
- Virtual Planet Laboratory, University of Washington, Seattle, Washington, USA
| | - Patrick Dunn
- Space Sciences Laboratory, University of California, Berkeley, Berkeley, California, USA
| | - Madeline Christensen
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Bellarmine Preparatory, Tacoma, Washington, USA
| | - Chuanfei Dong
- Department of Astrophysical Sciences, Princeton University, Princeton, California, USA
| | - Renyu Hu
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Yuk Yung
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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Moses JI, Cavalié T, Fletcher LN, Roman MT. Atmospheric chemistry on Uranus and Neptune. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190477. [PMID: 33161866 PMCID: PMC7658780 DOI: 10.1098/rsta.2019.0477] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/16/2020] [Indexed: 05/04/2023]
Abstract
Comparatively little is known about atmospheric chemistry on Uranus and Neptune, because remote spectral observations of these cold, distant 'Ice Giants' are challenging, and each planet has only been visited by a single spacecraft during brief flybys in the 1980s. Thermochemical equilibrium is expected to control the composition in the deeper, hotter regions of the atmosphere on both planets, but disequilibrium chemical processes such as transport-induced quenching and photochemistry alter the composition in the upper atmospheric regions that can be probed remotely. Surprising disparities in the abundance of disequilibrium chemical products between the two planets point to significant differences in atmospheric transport. The atmospheric composition of Uranus and Neptune can provide critical clues for unravelling details of planet formation and evolution, but only if it is fully understood how and why atmospheric constituents vary in a three-dimensional sense and how material coming in from outside the planet affects observed abundances. Future mission planning should take into account the key outstanding questions that remain unanswered about atmospheric chemistry on Uranus and Neptune, particularly those questions that pertain to planet formation and evolution, and those that address the complex, coupled atmospheric processes that operate on Ice Giants within our solar system and beyond. This article is part of a discussion meeting issue 'Future exploration of ice giant systems'.
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Affiliation(s)
- J. I. Moses
- Space Science Institute, 4765 Walnut Street, Suite B, Boulder, CO 80301, USA
| | - T. Cavalié
- Laboratoire d’Astrophysique de Bordeaux, University of Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
- LESIA, Observatoire de Paris, 92195 Meudon, France
| | - L. N. Fletcher
- School of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - M. T. Roman
- School of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
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Fletcher LN, de Pater I, Orton GS, Hofstadter MD, Irwin PGJ, Roman MT, Toledo D. Ice Giant Circulation Patterns: Implications for Atmospheric Probes. SPACE SCIENCE REVIEWS 2020; 216:21. [PMID: 32165773 PMCID: PMC7040070 DOI: 10.1007/s11214-020-00646-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 02/15/2020] [Indexed: 05/04/2023]
Abstract
Atmospheric circulation patterns derived from multi-spectral remote sensing can serve as a guide for choosing a suitable entry location for a future in situ probe mission to the Ice Giants. Since the Voyager-2 flybys in the 1980s, three decades of observations from ground- and space-based observatories have generated a picture of Ice Giant circulation that is complex, perplexing, and altogether unlike that seen on the Gas Giants. This review seeks to reconcile the various competing circulation patterns from an observational perspective, accounting for spatially-resolved measurements of: zonal albedo contrasts and banded appearances; cloud-tracked zonal winds; temperature and para-H2 measurements above the condensate clouds; and equator-to-pole contrasts in condensable volatiles (methane, ammonia, and hydrogen sulphide) in the deeper troposphere. These observations identify three distinct latitude domains: an equatorial domain of deep upwelling and upper-tropospheric subsidence, potentially bounded by peaks in the retrograde zonal jet and analogous to Jovian cyclonic belts; a mid-latitude transitional domain of upper-tropospheric upwelling, vigorous cloud activity, analogous to Jovian anticyclonic zones; and a polar domain of strong subsidence, volatile depletion, and small-scale (and potentially seasonally-variable) convective activity. Taken together, the multi-wavelength observations suggest a tiered structure of stacked circulation cells (at least two in the troposphere and one in the stratosphere), potentially separated in the vertical by (i) strong molecular weight gradients associated with cloud condensation, and by (ii) transitions from a thermally-direct circulation regime at depth to a wave- and radiative-driven circulation regime at high altitude. The inferred circulation can be tested in the coming decade by 3D numerical simulations of the atmosphere, and by observations from future world-class facilities. The carrier spacecraft for any probe entry mission must ultimately carry a suite of remote-sensing instruments capable of fully constraining the atmospheric motions at the probe descent location.
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Affiliation(s)
- Leigh N. Fletcher
- School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Imke de Pater
- Department of Astronomy, University of California, 501 Campbell Hall, Berkeley, CA 94720 USA
| | - Glenn S. Orton
- Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 USA
| | | | - Patrick G. J. Irwin
- Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford, OX1 3PU UK
| | - Michael T. Roman
- School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Daniel Toledo
- Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford, OX1 3PU UK
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Fletcher LN, de Pater I, Orton GS, Hofstadter MD, Irwin PGJ, Roman MT, Toledo D. Ice Giant Circulation Patterns: Implications for Atmospheric Probes. SPACE SCIENCE REVIEWS 2020. [PMID: 32165773 DOI: 10.1007/s11214-019-0619-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Atmospheric circulation patterns derived from multi-spectral remote sensing can serve as a guide for choosing a suitable entry location for a future in situ probe mission to the Ice Giants. Since the Voyager-2 flybys in the 1980s, three decades of observations from ground- and space-based observatories have generated a picture of Ice Giant circulation that is complex, perplexing, and altogether unlike that seen on the Gas Giants. This review seeks to reconcile the various competing circulation patterns from an observational perspective, accounting for spatially-resolved measurements of: zonal albedo contrasts and banded appearances; cloud-tracked zonal winds; temperature and para-H2 measurements above the condensate clouds; and equator-to-pole contrasts in condensable volatiles (methane, ammonia, and hydrogen sulphide) in the deeper troposphere. These observations identify three distinct latitude domains: an equatorial domain of deep upwelling and upper-tropospheric subsidence, potentially bounded by peaks in the retrograde zonal jet and analogous to Jovian cyclonic belts; a mid-latitude transitional domain of upper-tropospheric upwelling, vigorous cloud activity, analogous to Jovian anticyclonic zones; and a polar domain of strong subsidence, volatile depletion, and small-scale (and potentially seasonally-variable) convective activity. Taken together, the multi-wavelength observations suggest a tiered structure of stacked circulation cells (at least two in the troposphere and one in the stratosphere), potentially separated in the vertical by (i) strong molecular weight gradients associated with cloud condensation, and by (ii) transitions from a thermally-direct circulation regime at depth to a wave- and radiative-driven circulation regime at high altitude. The inferred circulation can be tested in the coming decade by 3D numerical simulations of the atmosphere, and by observations from future world-class facilities. The carrier spacecraft for any probe entry mission must ultimately carry a suite of remote-sensing instruments capable of fully constraining the atmospheric motions at the probe descent location.
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Affiliation(s)
- Leigh N Fletcher
- 1School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Imke de Pater
- 3Department of Astronomy, University of California, 501 Campbell Hall, Berkeley, CA 94720 USA
| | - Glenn S Orton
- 2Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 USA
| | - Mark D Hofstadter
- 2Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 USA
| | - Patrick G J Irwin
- 4Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford, OX1 3PU UK
| | - Michael T Roman
- 1School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Daniel Toledo
- 4Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford, OX1 3PU UK
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8
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Global-mean Vertical Tracer Mixing in Planetary Atmospheres. I. Theory and Fast-rotating Planets. ACTA ACUST UNITED AC 2018. [DOI: 10.3847/1538-4357/aada85] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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9
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Moses JI, Poppe AR. Dust Ablation on the Giant Planets: Consequences for Stratospheric Photochemistry. ICARUS 2017; 297:33-58. [PMID: 30842686 PMCID: PMC6398964 DOI: 10.1016/j.icarus.2017.06.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Ablation of interplanetary dust supplies oxygen to the upper atmospheres of Jupiter, Saturn, Uranus, and Neptune. Using recent dynamical model predictions for the dust influx rates to the giant planets (Poppe, A.R. et al. [2016], Icarus 264, 369), we calculate the ablation profiles and investigate the subsequent coupled oxygen-hydrocarbon neutral photochemistry in the stratospheres of these planets. We find that dust grains from the Edgeworth-Kuiper Belt, Jupiter-family comets, and Oort-cloud comets supply an effective oxygen influx rate of1.0 - 0.7 + 2.2 × 10 7 O atoms cm-2 s-1 to Jupiter,7.4 - 5.1 + 16 × 10 4 cm-2 s-1 to Saturn,8.9 - 6.1 + 19 × 10 4 cm-2 s-1 to Uranus, and7.5 - 5.1 + 16 × 10 5 cm-2 s-1 to Neptune. The fate of the ablated oxygen depends in part on the molecular/atomic form of the initially delivered products, and on the altitude at which it was deposited. The dominant stratospheric products are CO, H2O, and CO2, which are relatively stable photochemically. Model-data comparisons suggest that interplanetary dust grains deliver an important component of the external oxygen to Jupiter and Uranus but fall far short of the amount needed to explain the CO abundance currently seen in the middle stratospheres of Saturn and Neptune. Our results are consistent with the theory that all of the giant planets have experienced large cometary impacts within the last few hundred years. Our results also suggest that the low background H2O abundance in Jupiter's stratosphere is indicative of effective conversion of meteoric oxygen to CO during or immediately after the ablation process - photochemistry alone cannot efficiently convert the H2O into CO on the giant planets.
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Affiliation(s)
- Julianne I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - Andrew R Poppe
- Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720, USA
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10
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VULCAN
: An Open-source, Validated Chemical Kinetics
Python
Code for Exoplanetary Atmospheres. ACTA ACUST UNITED AC 2017. [DOI: 10.3847/1538-4365/228/2/20] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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11
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NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROMHST/WFC3 SPECTROSCOPY. ACTA ACUST UNITED AC 2016. [DOI: 10.3847/0004-6256/152/6/203] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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12
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Moses JI, Marley MS, Zahnle K, Line MR, Fortney JJ, Barman TS, Visscher C, Lewis NK, Wolff MJ. ON THE COMPOSITION OF YOUNG, DIRECTLY IMAGED GIANT PLANETS. THE ASTROPHYSICAL JOURNAL 2016; 829:66. [PMID: 31171882 PMCID: PMC6547835 DOI: 10.3847/0004-637x/829/2/66] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The past decade has seen significant progress on the direct detection and characterization of young, self-luminous giant planets at wide orbital separations from their host stars. Some of these planets show evidence for disequilibrium processes like transport-induced quenching in their atmospheres; photochemistry may also be important, despite the large orbital distances. These disequilibrium chemical processes can alter the expected composition, spectral behavior, thermal structure, and cooling history of the planets, and can potentially confuse determinations of bulk elemental ratios, which provide important insights into planet-formation mechanisms. Using a thermo/photochemical kinetics and transport model, we investigate the extent to which disequilibrium chemistry affects the composition and spectra of directly imaged giant exoplanets. Results for specific "young Jupiters" such as HR 8799 b and 51 Eri b are presented, as are general trends as a function of planetary effective temperature, surface gravity, incident ultraviolet flux, and strength of deep atmospheric convection. We find that quenching is very important on young Jupiters, leading to CO/CH4 and N2/NH3 ratios much greater than, and H2O mixing ratios a factor of a few less than, chemical-equilibrium predictions. Photochemistry can also be important on such planets, with CO2 and HCN being key photochemical products. Carbon dioxide becomes a major constituent when stratospheric temperatures are low and recycling of water via the H2 + OH reaction becomes kinetically stifled. Young Jupiters with effective temperatures ≲700 K are in a particularly interesting photochemical regime that differs from both transiting hot Jupiters and our own solar-system giant planets.
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Affiliation(s)
- J I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - M S Marley
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - K Zahnle
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - M R Line
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
| | - J J Fortney
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
| | - T S Barman
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
| | - C Visscher
- Dordt College, Sioux Center, IA 51250, USA and Space Science Institute, Boulder, CO 80301, USA
| | - N K Lewis
- Space Telescope Science Institute, Baltimore, MD 21218, USA
| | - M J Wolff
- Space Science Institute, Boulder, CO 80301, USA
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13
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14
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Dalba PA, Muirhead PS, Fortney JJ, Hedman MM, Nicholson PD, Veyette MJ. THE TRANSIT TRANSMISSION SPECTRUM OF A COLD GAS GIANT PLANET. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/814/2/154] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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15
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Mandt K, Mousis O, Marty B, Cavalié T, Harris W, Hartogh P, Willacy K. Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites. SPACE SCIENCE REVIEWS 2015; 197:297-342. [PMID: 31105346 PMCID: PMC6525011 DOI: 10.1007/s11214-015-0161-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Comets play a dual role in understanding the formation and evolution of the solar system. First, the composition of comets provides information about the origin of the giant planets and their moons because comets formed early and their composition is not expected to have evolved significantly since formation. They, therefore serve as a record of conditions during the early stages of solar system formation. Once comets had formed, their orbits were perturbed allowing them to travel into the inner solar system and impact the planets. In this way they contributed to the volatile inventory of planetary atmospheres. We review here how knowledge of comet composition up to the time of the Rosetta mission has contributed to understanding the formation processes of the giant planets, their moons and small icy bodies in the solar system. We also discuss how comets contributed to the volatile inventories of the giant and terrestrial planets.
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Affiliation(s)
- K.E. Mandt
- Southwest Research Institute, San Antonio, TX, USA
| | - O. Mousis
- Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388, Marseille, France
| | - B. Marty
- CRPG-CNRS, Nancy-Université, Vandoeuvre-lès-Nancy, France
| | - T. Cavalié
- Max Planck Institute for Solar System Research, Göttingen, Germany
| | - W. Harris
- University of Arizona, Tucson, AZ, USA
| | - P. Hartogh
- Max Planck Institute for Solar System Research, Göttingen, Germany
| | - K. Willacy
- Jet Propulsion Laboratory, Pasadena, CA, USA
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16
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Moses JI, Armstrong ES, Fletcher LN, Friedson AJ, Irwin PGJ, Sinclair JA, Hesman BE. Evolution of Stratospheric Chemistry in the Saturn Storm Beacon Region. ICARUS 2015; 261:149-168. [PMID: 30842685 PMCID: PMC6398963 DOI: 10.1016/j.icarus.2015.08.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The giant northern-hemisphere storm that erupted on Saturn in December 2010 triggered significant changes in stratospheric temperatures and species abundances that persisted for more than a year after the original outburst. The stratospheric regions affected by the storm have been nicknamed "beacons" due to their prominent infrared-emission signatures (Fletcher, L.N. et al. [2011]. Science 332, 1413). The two beacon regions that were present initially merged in April 2011 to form a single, large, anticyclonic vortex (Fletcher, L.N. et al. [2012]. Icarus 221, 560). We model the expected photochemical evolution of the stratospheric constituents in the beacons from the initial storm onset through the merger and on out to March 2012. The results are compared with longitudinally resolved Cassini/CIRS spectra from May 2011. If we ignore potential changes due to vertical winds within the beacon, we find that C2H2, C2H6, and C3H8 remain unaffected by the increased stratospheric temperatures in the beacon, the abundance of the shorter-lived CH3C2H decreases, and the abundance of C2H4 increases significantly due to the elevated temperatures, the latter most notably in a secondary mixing-ratio peak located near mbar pressures. The C4H2 abundance in the model decreases by a factor of a few in the 0.01-10 mbar region but has a significant increase in the 10-30 mbar region due to evaporation of the previously condensed phase. The column abundances of C6H6 and H2O above ~30 mbar also increase due to aerosol evaporation. Model-data comparisons show that models that consider temperature changes alone underpredict the abundance of C2H x species by a factor of 2-7 in the beacon core in May 2011, suggesting that other processes not considered by the models, such as downwelling winds in the vortex, are affecting the species profiles. Additional calculations indicate that downwelling winds of order -10 cm s -1 near ~0.1 mbar need to be included in the photochemical models in order to explain the inferred C2H x abundances in the beacon core, indicating that both strong subsiding winds and chemistry at elevated temperatures are affecting the vertical profiles of atmospheric constituents in the beacon. We (i) discuss the general chemical behavior of stratospheric species in the beacon region, (ii) demonstrate how the evolving beacon environment affects the species vertical profiles and emission characteristics (both with and without the presence of vertical winds), (iii) make predictions with respect to compositional changes that can be tested against Cassini and Herschel data, and higher-spectral-resolution ground-based observations of the beacon region, and (iv) discuss future measurements and modeling that could further our understanding of the dynamical origin, evolution, and chemical processing within these unexpected stratospheric vortices that were generated after the 2010 convective event.
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Affiliation(s)
- Julianne I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - Eleanor S Armstrong
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | - Leigh N Fletcher
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | | | - Patrick G J Irwin
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | - James A Sinclair
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | - Brigette E Hesman
- Department of Astronomy, University of Maryland, College Park, MD, 20742, USA
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17
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Li C, Zhang X, Gao P, Yung Y. VERTICAL DISTRIBUTION OF
C
3
-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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18
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Moses JI. Chemical kinetics on extrasolar planets. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130073. [PMID: 24664912 PMCID: PMC6380885 DOI: 10.1098/rsta.2013.0073] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Chemical kinetics plays an important role in controlling the atmospheric composition of all planetary atmospheres, including those of extrasolar planets. For the hottest exoplanets, the composition can closely follow thermochemical-equilibrium predictions, at least in the visible and infrared photosphere at dayside (eclipse) conditions. However, for atmospheric temperatures approximately <2000K, and in the uppermost atmosphere at any temperature, chemical kinetics matters. The two key mechanisms by which kinetic processes drive an exoplanet atmosphere out of equilibrium are photochemistry and transport-induced quenching. I review these disequilibrium processes in detail, discuss observational consequences and examine some of the current evidence for kinetic processes on extrasolar planets.
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Affiliation(s)
- Julianne I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
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19
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Fletcher LN, Irwin PGJ, Barstow JK, de Kok RJ, Lee JM, Aigrain S. Exploring the diversity of Jupiter-class planets. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130064. [PMID: 24664910 PMCID: PMC3982424 DOI: 10.1098/rsta.2013.0064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Of the 900+ confirmed exoplanets discovered since 1995 for which we have constraints on their mass (i.e. not including Kepler candidates), 75% have masses larger than Saturn (0.3 MJ), 53% are more massive than Jupiter and 67% are within 1 AU of their host stars. When Kepler candidates are included, Neptune-sized giant planets could form the majority of the planetary population. And yet the term 'hot Jupiter' fails to account for the incredible diversity of this class of astrophysical object, which exists on a continuum of giant planets from the cool jovians of our own Solar System to the highly irradiated, tidally locked hot roasters. We review theoretical expectations for the temperatures, molecular composition and cloud properties of hydrogen-dominated Jupiter-class objects under a variety of different conditions. We discuss the classification schemes for these Jupiter-class planets proposed to date, including the implications for our own Solar System giant planets and the pitfalls associated with compositional classification at this early stage of exoplanetary spectroscopy. We discuss the range of planetary types described by previous authors, accounting for (i) thermochemical equilibrium expectations for cloud condensation and favoured chemical stability fields; (ii) the metallicity and formation mechanism for these giant planets; (iii) the importance of optical absorbers for energy partitioning and the generation of a temperature inversion; (iv) the favoured photochemical pathways and expectations for minor species (e.g. saturated hydrocarbons and nitriles); (v) the unexpected presence of molecules owing to vertical mixing of species above their quench levels; and (vi) methods for energy and material redistribution throughout the atmosphere (e.g. away from the highly irradiated daysides of close-in giants). Finally, we discuss the benefits and potential flaws of retrieval techniques for establishing a family of atmospheric solutions that reproduce the available data, and the requirements for future spectroscopic characterization of a set of Jupiter-class objects to test our physical and chemical understanding of these planets.
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Affiliation(s)
- Leigh N. Fletcher
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK
| | - Patrick G. J. Irwin
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK
| | - Joanna K. Barstow
- Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
| | - Remco J. de Kok
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
| | - Jae-Min Lee
- Institute for Theoretical Physics, University of Zurich, 8057 Zurich, Switzerland
| | - Suzanne Aigrain
- Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
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20
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Telling J, Lacrampe-Couloume G, Sherwood Lollar B. Carbon and hydrogen isotopic composition of methane and C2+ alkanes in electrical spark discharge: implications for identifying sources of hydrocarbons in terrestrial and extraterrestrial settings. ASTROBIOLOGY 2013; 13:483-490. [PMID: 23683048 DOI: 10.1089/ast.2012.0915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The low-molecular-weight alkanes--methane, ethane, propane, and butane--are found in a wide range of terrestrial and extraterrestrial settings. The development of robust criteria for distinguishing abiogenic from biogenic alkanes is essential for current investigations of Mars' atmosphere and for future exobiology missions to other planets and moons. Here, we show that alkanes synthesized during gas-phase radical recombination reactions in electrical discharge experiments have values of δ(2)H(methane)>δ(2)H(ethane)>δ(2)H(propane), similar to those of the carbon isotopes. The distribution of hydrogen isotopes in gas-phase radical reactions is likely due to kinetic fractionations either (i) from the preferential incorporation of (1)H into longer-chain alkanes due to the more rapid rate of collisions of the smaller (1)H-containing molecules or (ii) by secondary ion effects. Similar δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns may be expected in a range of extraterrestrial environments where gas-phase radical reactions dominate, including interstellar space, the atmosphere and liquid hydrocarbon lakes of Saturn's moon Titan, and the outer atmospheres of Jupiter, Saturn, Neptune, and Uranus. Radical recombination reactions at high temperatures and pressures may provide an explanation for the combined reversed δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns of terrestrial alkanes documented at a number of high-temperature/pressure crustal sites.
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Affiliation(s)
- Jon Telling
- Department of Earth Sciences, University of Toronto, Toronto, Canada.
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21
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Moses JI, Madhusudhan N, Visscher C, Freedman RS. CHEMICAL CONSEQUENCES OF THE C/O RATIO ON HOT JUPITERS: EXAMPLES FROM WASP-12b, COROT-2b, XO-1b, AND HD 189733b. THE ASTROPHYSICAL JOURNAL 2012; 763:25. [PMID: 30842680 PMCID: PMC6398958 DOI: 10.1088/0004-637x/763/1/25] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Motivated by recent spectroscopic evidence for carbon-rich atmospheres on some transiting exo-planets, we investigate the influence of the C/O ratio on the chemistry, composition, and spectra of extrasolar giant planets both from a thermochemical-equilibrium perspective and from consideration of disequilibrium processes like photochemistry and transport-induced quenching. We find that although CO is predicted to be a major atmospheric constituent on hot Jupiters for all C/O ratios, other oxygen-bearing molecules like H2O and CO2 are much more abundant when C/O < 1, whereas CH4, HCN, and C2H2 gain significantly in abundance when C/O > 1. Other notable species like N2 and NH3 that do not contain carbon or oxygen are relatively unaffected by the C/O ratio. Disequilibrium processes tend to enhance the abundance of CH4, NH3, HCN, and C2H2 over a wide range of C/O ratios. We compare the results of our models with secondary-eclipse photometric data from the Spitzer Space Telescope and conclude that (1) disequilibrium models with C/O ~ 1 are consistent with spectra of WASP-12b, XO-1b, and CoRoT-2b, confirming the possible carbon-rich nature of these planets, (2) spectra from HD 189733b are consistent with C/O ≲ 1, but as the assumed metallicity is increased above solar, the required C/O ratio must increase toward 1 to prevent too much H2O absorption, (3) species like HCN can have a significant influence on spectral behavior in the 3.6 and 8.0 μm Spitzer channels, potentially providing even more opacity than CH4 when C/O > 1, and (4) the very high CO2 abundance inferred for HD 189733b from near-infrared observations cannot be explained through equilibrium or disequilibrium chemistry in a hydrogen-dominated atmosphere. We discuss possible formation mechanisms for carbon-rich hot Jupiters, including scenarios in which the accretion of CO-rich, H2O-poor gas dominates the atmospheric envelope, and scenarios in which the planets accrete carbon-rich solids while migrating through disk regions inward of the snow line. The C/O ratio and bulk atmospheric metallicity provide important clues regarding the formation and evolution of the giant planets.
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Affiliation(s)
- J I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO, 80301, USA
| | - N Madhusudhan
- Department of Physics and Department of Astronomy, Yale University, New Haven, CT, 06520-8101, USA
| | - C Visscher
- Southwest Research Institute, Boulder, CO, 80302, USA
| | - R S Freedman
- SETI Institute, Mountain View, CA, 94043 and NASA Ames Research Center, Moffett Field, CA, 94035, USA
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Gustin J, Bonfond B, Grodent D, Gérard JC. Conversion from HST ACS and STIS auroral counts into brightness, precipitated power, and radiated power for H2giant planets. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012ja017607] [Citation(s) in RCA: 55] [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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23
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Moses JI, Visscher C, Keane TC, Sperier A. On the abundance of non-cometary HCN on Jupiter. Faraday Discuss 2011; 147:103-36; discussion 251-82. [PMID: 21302544 DOI: 10.1039/c003954c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using one-dimensional thermochemical/photochemical kinetics and transport models, we examine the chemistry of nitrogen-bearing species in the Jovian troposphere in an attempt to explain the low observational upper limit for HCN. We track the dominant mechanisms for interconversion of N2-NH3 and HCN-NH3 in the deep, high-temperature troposphere and predict the rate-limiting step for the quenching of HCN at cooler tropospheric altitudes. Consistent with some other investigations that were based solely on time-scale arguments, our models suggest that transport-induced quenching of thermochemically derived HCN leads to very small predicted mole fractions of hydrogen cyanide in Jupiter's upper troposphere. By the same token, photochemical production of HCN is ineffective in Jupiter's troposphere: CH4-NH3 coupling is inhibited by the physical separation of the CH4 photolysis region in the upper stratosphere from the NH3 photolysis and condensation region in the troposphere, and C2H2-NH3 coupling is inhibited by the low tropospheric abundance of C2H2. The upper limits from infrared and submillimetre observations can be used to place constraints on the production of HCN and other species from lightning and thundershock sources.
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Affiliation(s)
- Julianne I Moses
- Space Science Institute, 1602 Old Orchard Ln, Seabrook, TX 77586, USA.
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Moses JI. Latitudinal and seasonal models of stratospheric photochemistry on Saturn: Comparison with infrared data from IRTF/TEXES. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2005je002450] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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