1
|
Elowitz M, Sivaraman B, Hendrix A, Lo JI, Chou SL, Cheng BM, Sekhar BNR, Mason NJ. Possible detection of hydrazine on Saturn's moon Rhea. SCIENCE ADVANCES 2021; 7:eaba5749. [PMID: 33523937 PMCID: PMC10670839 DOI: 10.1126/sciadv.aba5749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
We present the first analysis of far-ultraviolet reflectance spectra of regions on Rhea's leading and trailing hemispheres collected by the Cassini Ultraviolet Imaging Spectrograph during targeted flybys. In particular, we aim to explain the unidentified broad absorption feature centred near 184 nm. We have used laboratory measurements of the UV spectroscopy of a set of candidate molecules and found a good fit to Rhea's spectra with both hydrazine monohydrate and several chlorine-containing molecules. Given the radiation-dominated chemistry on the surface of icy satellites embedded within their planets' magnetospheres, hydrazine monohydrate is argued to be the most plausible candidate for explaining the absorption feature at 184 nm. Hydrazine was also used as a propellant in Cassini's thrusters, but the thrusters were not used during icy satellite flybys and thus the signal is believed to not arise from spacecraft fuel. We discuss how hydrazine monohydrate may be chemically produced on icy surfaces.
Collapse
Affiliation(s)
- Mark Elowitz
- Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
| | - Bhalamurugan Sivaraman
- Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad 380 009, India.
| | | | - Jen-Iu Lo
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Sheng-Lung Chou
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Bing-Ming Cheng
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - B N Raja Sekhar
- B-1, Indus-1, Atomic and Molecular Physics Division, Bhabha Atomic Research Centre at RRCAT, Indore, India
| | - Nigel J Mason
- School of Physical Sciences, The University of Kent, Canterbury CT2 7NH, UK
| |
Collapse
|
2
|
Abstract
The kinetic Monte Carlo method, used in astrochemistry to investigate suprathermal (hot) particles at the molecular level, is presented. Different modifications of this method, aimed at studying the influence of suprathermal particles in the processes occurring in gas and dust envelopes surrounding astrophysical objects — prestellar and protostellar cores of molecular clouds, planets, their moons, and comets in the Solar and extrasolar planetary systems — are considered. The important role of the fraction of suprathermal particles in astrochemical applications of this approach is demonstrated. The presence of these particles leads to local changes in the chemical composition; causes non-thermal emissions in gas and dust envelopes; enhances the chemical exchange between the gas and dust fractions of envelope; leads to the formation of extended hot coronae of planets; increases non-thermal atmospheric losses, thus determining the evolution of planetary atmosphere on astronomical time scales; and facilitates the formation of complex molecules in gas and dust envelopes of astrophysical objects.
The bibliography includes 146 references.
Collapse
|
3
|
|
4
|
Smith AW, Jackman CM, Thomsen MF. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2016; 121:2984-3005. [PMID: 27867795 PMCID: PMC5111619 DOI: 10.1002/2015ja022005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 02/01/2016] [Accepted: 03/03/2016] [Indexed: 05/04/2023]
Abstract
Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north-south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30RS downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.
Collapse
Affiliation(s)
- A. W. Smith
- Department of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
| | - C. M. Jackman
- Department of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
| | | |
Collapse
|
5
|
Mandt K, Mousis O, Chassefière E. Comparative planetology of the history of nitrogen isotopes in the atmospheres of Titan and Mars. ICARUS 2015; 254:259-261. [PMID: 31118538 PMCID: PMC6527424 DOI: 10.1016/j.icarus.2015.03.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We present here a comparative planetology study of evolution of 14N/15N at Mars and Titan. Studies show that 14N/15N can evolve a great deal as a result of escape in the atmosphere of Mars, but not in Titan's atmosphere. We explain this through the existence of an upper limit to the amount of fractionation allowed to occur due to escape that is a function of the escape flux and the column density of nitrogen.
Collapse
Affiliation(s)
- Kathleen Mandt
- Space Science and Engineering Division, Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78228, United States
| | - Olivier Mousis
- Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
| | - Eric Chassefière
- Univ Paris-Sud, Laboratoire GEOPS, UMR 8148, Université Paris-Sud, CNRS, Orsay F-91405, France
| |
Collapse
|
6
|
Mandt KE, Mousis O, Lunine J, Gautier D. PROTOSOLAR AMMONIA AS THE UNIQUE SOURCE OF TITAN's NITROGEN. THE ASTROPHYSICAL JOURNAL. LETTERS 2014; 788:L24. [PMID: 31069045 PMCID: PMC6501209 DOI: 10.1088/2041-8205/788/2/l24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The origin of Titan's nitrogen-rich atmosphere is thought to be ammonia ice, but this has not yet been confirmed. Furthermore, it is uncertain whether the building blocks of Titan formed within the Saturnian subnebula or in the colder protosolar nebula (PSN). Recent measurements of the nitrogen isotope ratio in cometary ammonia, combined with evolutionary constraints on the nitrogen isotopes in Titan's atmosphere provide firm evidence that the nitrogen in Titan's atmosphere must have originated as ammonia ice formed in the PSN under conditions similar to that of cometary formation. This result has important implications for the projected D/H ratio in cometary methane, nitrogen isotopic fractionation in the PSN and the source of nitrogen for Earth's atmosphere.
Collapse
Affiliation(s)
- Kathleen E Mandt
- Space Science and Engineering Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228, USA
| | - Olivier Mousis
- Université de Franche-Comté, Institut UTINAM, CNRS/INSU, UMR 6213, Observatoire des Sciences de l'Univers de Besancon, France
| | - Jonathan Lunine
- Cornell University, Center for Radiophysics and Space Research, Ithaca, NY, USA
| | - Daniel Gautier
- Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris, France
| |
Collapse
|
7
|
Richard MS, Cravens TE, Robertson IP, Waite JH, Wahlund JE, Crary FJ, Coates AJ. Energetics of Titan's ionosphere: Model comparisons with Cassini data. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011ja016603] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- M. S. Richard
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - I. P. Robertson
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - J. H. Waite
- Southwest Research Institute; San Antonio Texas USA
| | | | - F. J. Crary
- Southwest Research Institute; San Antonio Texas USA
| | - A. J. Coates
- Mullard Space Science Laboratory, Holmbury St. Mary; University College London; Dorking, Surrey UK
| |
Collapse
|
8
|
Westlake JH, Bell JM, Waite JH, Johnson RE, Luhmann JG, Mandt KE, Magee BA, Rymer AM. Titan's thermospheric response to various plasma environments. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010ja016251] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- J. H. Westlake
- Department of Physics and Astronomy; University of Texas at San Antonio; San Antonio Texas USA
| | - J. M. Bell
- Space Science and Engineering Division; Southwest Research Institute; San Antonio Texas USA
| | - J. H. Waite
- Department of Physics and Astronomy; University of Texas at San Antonio; San Antonio Texas USA
- Space Science and Engineering Division; Southwest Research Institute; San Antonio Texas USA
| | - R. E. Johnson
- Engineering Physics Program; University of Virginia; Charlottesville Virginia USA
| | - J. G. Luhmann
- Space Sciences Laboratory; University of California; Berkeley California USA
| | - K. E. Mandt
- Space Science and Engineering Division; Southwest Research Institute; San Antonio Texas USA
- Department of Environmental and Civil Engineering; University of Texas at San Antonio; San Antonio Texas USA
| | - B. A. Magee
- Space Science and Engineering Division; Southwest Research Institute; San Antonio Texas USA
| | - A. M. Rymer
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| |
Collapse
|
9
|
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]
|
10
|
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]
|
11
|
Ma YJ, Russell CT, Nagy AF, Toth G, Bertucci C, Dougherty MK, Neubauer FM, Wellbrock A, Coates AJ, Garnier P, Wahlund JE, Cravens TE, Crary FJ. Time-dependent global MHD simulations of Cassini T32 flyby: From magnetosphere to magnetosheath. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013676] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Y. J. Ma
- Institute of Geophysics and Planetary Physics; University of California Los Angeles; Los Angeles California USA
| | - C. T. Russell
- Institute of Geophysics and Planetary Physics; University of California Los Angeles; Los Angeles California USA
| | - A. F. Nagy
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - G. Toth
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - C. Bertucci
- Blackett Laboratory, Space and Atmospheric Physics Group; Imperial College London; London UK
| | - M. K. Dougherty
- Blackett Laboratory, Space and Atmospheric Physics Group; Imperial College London; London UK
| | - F. M. Neubauer
- Institute of Geophysics and Meteorology; University of Cologne; Cologne Germany
| | - A. Wellbrock
- Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London; London UK
| | - A. J. Coates
- Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London; London UK
| | - P. Garnier
- Swedish Institute of Space Physics; Uppsala Sweden
| | | | - T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - F. J. Crary
- Southwest Research Institute; San Antonio Texas USA
| |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- Robert E Johnson
- University of Virginia, Charlottesville, VA 22904, USA Department of Physics, New York University, New York, NY 10003, USA.
| |
Collapse
|
13
|
Dandouras I, Garnier P, Mitchell DG, Roelof EC, Brandt PC, Krupp N, Krimigis SM. Titan's exosphere and its interaction with Saturn's magnetosphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:743-752. [PMID: 19073465 DOI: 10.1098/rsta.2008.0249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly charged energetic ions from Saturn's magnetosphere undergo charge-exchange collisions with neutral atoms in Titan's upper atmosphere, or exosphere, being transformed into energetic neutral atoms (ENAs). The ion and neutral camera, one of the three sensors that comprise the magnetosphere imaging instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images these ENAs like photons, and measures their fluxes and energies. These remote-sensing measurements, combined with the in situ measurements performed in the upper thermosphere and in the exosphere by the ion and neutral mass spectrometer instrument, provide a powerful diagnostic of Titan's exosphere and its interaction with the Kronian magnetosphere. These observations are analysed and some of the exospheric features they reveal are modelled.
Collapse
Affiliation(s)
- Iannis Dandouras
- Centre d'Etude Spatiale des Rayonnements, Université de Toulouse, 31028 Toulouse, France CNRS, UMR 5187, 31028 Toulouse, France.
| | | | | | | | | | | | | |
Collapse
|
14
|
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
| |
Collapse
|
15
|
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]
|
16
|
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]
|