1
|
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: 7] [Impact Index Per Article: 1.0] [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.
Collapse
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
| |
Collapse
|
2
|
Affiliation(s)
- Rommel B. Viana
- Departamento de Química e Física Molecular, Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, Brazil
| |
Collapse
|
3
|
Felici M, Arridge CS, Coates AJ, Badman SV, Dougherty MK, Jackman CM, Kurth WS, Melin H, Mitchell DG, Reisenfeld DB, Sergis N. Cassini observations of ionospheric plasma in Saturn's magnetotail lobes. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2016; 121:338-357. [PMID: 27610291 PMCID: PMC4994772 DOI: 10.1002/2015ja021648] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 12/13/2015] [Accepted: 12/28/2015] [Indexed: 05/20/2023]
Abstract
Studies of Saturn's magnetosphere with the Cassini mission have established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere. It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn. In this paper we describe a case study of data from Saturn's magnetotail, when Cassini was located at ≃ 2200 h Saturn local time at 36 RS from Saturn. During several entries into the magnetotail lobe, tailward flowing cold electrons and a cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The electrons and ions appear to be dispersed, dropping to lower energies with time. The composition of both the plasma sheet and lobe ions show very low fluxes (sometimes zero within measurement error) of water group ions. The magnetic field has a swept-forward configuration which is atypical for this region, and the total magnetic field strength is larger than expected at this distance from the planet. Ultraviolet auroral observations show a dawn brightening, and upstream heliospheric models suggest that the magnetosphere is being compressed by a region of high solar wind ram pressure. We interpret this event as the observation of ionospheric outflow in Saturn's magnetotail. We estimate a number flux between (2.95 ± 0.43) × 109 and (1.43 ± 0.21) × 1010 cm-2 s-1, 1 or about 2 orders of magnitude larger than suggested by steady state MHD models, with a mass source between 1.4 ×102 and 1.1 ×103 kg/s. After considering several configurations for the active atmospheric regions, we consider as most probable the main auroral oval, with associated mass source between 49.7 ±13.4 and 239.8 ±64.8 kg/s for an average auroral oval, and 10 ±4 and 49 ±23 kg/s for the specific auroral oval morphology found during this event. It is not clear how much of this mass is trapped within the magnetosphere and how much is lost to the solar wind.
Collapse
Affiliation(s)
- M. Felici
- Mullard Space Science LaboratoryUniversity College LondonDorkingUK
- Centre for Planetary Sciences at UCL/BirkbeckLondonUK
- Department of PhysicsLancaster UniversityLancasterUK
| | - C. S. Arridge
- Department of PhysicsLancaster UniversityLancasterUK
| | - A. J. Coates
- Mullard Space Science LaboratoryUniversity College LondonDorkingUK
- Centre for Planetary Sciences at UCL/BirkbeckLondonUK
| | - S. V. Badman
- Department of PhysicsLancaster UniversityLancasterUK
| | - M. K. Dougherty
- Space and Atmospheric Physics Group, The Blackett LaboratoryImperial College LondonLondonUK
| | - C. M. Jackman
- Department of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
| | - W. S. Kurth
- Department of Physics and AstronomyUniversity of IowaIowa CityIowaUSA
| | - H. Melin
- Department of Physics and AstronomyUniversity of LeicesterLeicesterUK
| | - D. G. Mitchell
- The Johns Hopkins University Applied Physics LaboratoryLaurelMarylandUSA
| | - D. B. Reisenfeld
- Department of Physics and AstronomyUniversity of MontanaMissoulaMontanaUSA
| | - N. Sergis
- Mullard Space Science LaboratoryUniversity College LondonDorkingUK
- Office for Space ResearchAcademy of AthensAthensGreece
| |
Collapse
|
4
|
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]
|
5
|
Yelle RV, McConnell JC, Sandel BR, Broadfoot AL. The dependence of electroglow on the solar flux. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p15110] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
6
|
Herbert F, Sandel BR, Yelle RV, Holberg JB, Broadfoot AL, Shemansky DE, Atreya SK, Romani PN. The upper atmosphere of Uranus: EUV occultations observed by Voyager 2. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p15093] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
7
|
Galand M, Moore L, Mueller-Wodarg I, Mendillo M, Miller S. Response of Saturn's auroral ionosphere to electron precipitation: Electron density, electron temperature, and electrical conductivity. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010ja016412] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Marina Galand
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Ingo Mueller-Wodarg
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Steve Miller
- Atmospheric Physics Laboratory, Department of Physics and Astronomy; University College London; London UK
| |
Collapse
|
8
|
Moore L, Mueller-Wodarg I, Galand M, Kliore A, Mendillo M. Latitudinal variations in Saturn's ionosphere: Cassini measurements and model comparisons. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010ja015692] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | | | - Marina Galand
- Department of Physics; Imperial College London; London UK
| | - Arvydas Kliore
- Radio Science Systems; Jet Propulsion Laboratory; Pasadena California USA
| | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
| |
Collapse
|
9
|
Broadfoot AL, Herbert F, Holberg JB, Hunten DM, Kumar S, Sandel BR, Shemansky DE, Smith GR, Yelle RV, Strobel DF, Moos HW, Donahue TM, Atreya SK, Bertaux JL, Blamont JE, McConnell JC, Dessler AJ, Linick S, Springer R. Ultraviolet spectrometer observations of uranus. Science 2010; 233:74-9. [PMID: 17812892 DOI: 10.1126/science.233.4759.74] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Data from solar and stellar occultations of Uranus indicate a temperature of about 750 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane and acetylene in the lower levels. The ultraviolet spectrum of the sunlit hemisphere is dominated by emissions from atomic and molecular hydrogen, which are kmown as electroglow emissions. The energy source for these emissions is unknown, but the spectrum implies excitation by low-energy electrons (modeled with a 3-electron-volt Maxwellian energy distribution). The major energy sink for the electrons is dissociation of molecular hydrogen, producing hydrogen atoms at a rate of 10(29) per second. Approximately half the atoms have energies higher than the escape energy. The high temperature of the atmosphere, the small size of Uranus, and the number density of hydrogen atoms in the thermosphere imply an extensive thermal hydrogen corona that reduces the orbital lifetime of ring particles and biases the size distribution toward larger particles. This corona is augmented by the nonthermal hydrogen atoms associated with the electroglow. An aurora near the magnetic pole in the dark hemisphere arises from excitation of molecular hydrogen at the level where its vertical column abundance is about 10(20) per square centimeter with input power comparable to that of the sunlit electroglow (approximately 2x10(11) watts). An initial estimate of the acetylene volume mixing ratio, as judged from measurements of the far ultraviolet albedo, is about 2 x 10(-7) at a vertical column abundance of molecular hydrogen of 10(23) per square centimeter (pressure, approximately 0.3 millibar). Carbon emissions from the Uranian atmosphere were also detected.
Collapse
|
10
|
Imanaka H, Smith MA. EUV Photochemical Production of Unsaturated Hydrocarbons: Implications to EUV Photochemistry in Titan and Jovian Planets. J Phys Chem A 2009; 113:11187-94. [DOI: 10.1021/jp9041952] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hiroshi Imanaka
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, Arizona 85721, and SETI Institute, 515 North Whisman Road, Mountain View, California 94043
| | - Mark A. Smith
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, Arizona 85721, and SETI Institute, 515 North Whisman Road, Mountain View, California 94043
| |
Collapse
|
11
|
Galand M, Moore L, Charnay B, Mueller-Wodarg I, Mendillo M. Solar primary and secondary ionization at Saturn. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013981] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Marina Galand
- Department of Physics; Imperial College London; London UK
| | - Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | | | | | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
| |
Collapse
|
12
|
Moore L, Galand M, Mueller-Wodarg I, Yelle R, Mendillo M. Plasma temperatures in Saturn's ionosphere. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008ja013373] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Luke Moore
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - Marina Galand
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
| | - Ingo Mueller-Wodarg
- Space and Atmospheric Physics Group, Department of Physics; Imperial College London; London UK
| | - Roger Yelle
- Lunar and Planetary Laboratory; University of Arizona; Tucson Arizona USA
| | - Michael Mendillo
- Center for Space Physics; Boston University; Boston Massachusetts USA
| |
Collapse
|
13
|
Smith CGA, Aylward AD, Millward GH, Miller S, Moore LE. An unexpected cooling effect in Saturn's upper atmosphere. Nature 2007; 445:399-401. [PMID: 17251972 DOI: 10.1038/nature05518] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Accepted: 12/08/2006] [Indexed: 11/08/2022]
Abstract
The upper atmospheres of the four Solar System giant planets exhibit high temperatures that cannot be explained by the absorption of sunlight. In the case of Saturn the temperatures predicted by models of solar heating are approximately 200 K, compared to temperatures of approximately 400 K observed independently in the polar regions and at 30 degrees latitude. This unexplained 'energy crisis' represents a major gap in our understanding of these planets' atmospheres. An important candidate for the source of the missing energy is the magnetosphere, which injects energy mostly in the polar regions of the planet. This polar energy input is believed to be sufficient to explain the observed temperatures, provided that it is efficiently redistributed globally by winds, a process that is not well understood. Here we show, using a numerical model, that the net effect of the winds driven by the polar energy inputs is not to heat but to cool the low-latitude thermosphere. This surprising result allows us to rule out known polar energy inputs as the solution to the energy crisis at Saturn. There is either an unknown--and large--source of polar energy, or, more probably, some other process heats low latitudes directly.
Collapse
Affiliation(s)
- C G A Smith
- Department of Physics and Astronomy, University College London, WC1E 6BT, UK
| | | | | | | | | |
Collapse
|
14
|
Glocer A, Gombosi TI, Toth G, Hansen KC, Ridley AJ, Nagy A. Polar wind outflow model: Saturn results. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006ja011755] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- A. Glocer
- Center for Space Environment Modeling; University of Michigan; Ann Arbor Michigan USA
| | - T. I. Gombosi
- Center for Space Environment Modeling; University of Michigan; Ann Arbor Michigan USA
| | - G. Toth
- Center for Space Environment Modeling; University of Michigan; Ann Arbor Michigan USA
| | - K. C. Hansen
- Center for Space Environment Modeling; University of Michigan; Ann Arbor Michigan USA
| | - A. J. Ridley
- Center for Space Environment Modeling; University of Michigan; Ann Arbor Michigan USA
| | - A. Nagy
- Center for Space Environment Modeling; University of Michigan; Ann Arbor Michigan USA
| |
Collapse
|
15
|
Moses JI, Fouchet T, Bézard B, Gladstone GR, Lellouch E, Feuchtgruber H. Photochemistry and diffusion in Jupiter's stratosphere: Constraints from ISO observations and comparisons with other giant planets. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2005je002411] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- J. I. Moses
- Lunar and Planetary Institute; Houston Texas USA
| | - T. Fouchet
- LESIA; Observatoire de Paris; Meudon France
- Université Paris 6; Paris France
| | - B. Bézard
- LESIA; Observatoire de Paris; Meudon France
| | - G. R. Gladstone
- Space Sciences Department; Southwest Research Institute; San Antonio Texas USA
| | | | - H. Feuchtgruber
- Max-Planck-Institut für Extraterrestrische Physik; Garching Germany
| |
Collapse
|
16
|
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]
|
17
|
|
18
|
Gérard JC. Characteristics of Saturn's FUV aurora observed with the Space Telescope Imaging Spectrograph. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004ja010513] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
19
|
Cody RJ, Romani PN, Nesbitt FL, Iannone MA, Tardy DC, Stief LJ. Rate constant for the reaction CH3+ CH3→ C2H6at T = 155 K and model calculation of the CH3abundance in the atmospheres of Saturn and Neptune. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002je002037] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
20
|
Moses JI, Bass SF. The effects of external material on the chemistry and structure of Saturn's ionosphere. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001172] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
21
|
Atreya SK, Wong MH, Owen TC, Mahaffy PR, Niemann HB, de Pater I, Drossart P, Encrenaz TH. A comparison of the atmospheres of Jupiter and Saturn: deep atmospheric composition, cloud structure, vertical mixing, and origin. PLANETARY AND SPACE SCIENCE 1999; 47:1243-1262. [PMID: 11543193 DOI: 10.1016/s0032-0633(99)00047-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We present our current understanding of the composition, vertical mixing, cloud structure and the origin of the atmospheres of Jupiter and Saturn. Available observations point to a much more vigorous vertical mixing in Saturn's middle-upper atmosphere than in Jupiter's. The nearly cloud-free nature of the Galileo probe entry site, a 5-micron hotspot, is consistent with the depletion of condensable volatiles to great depths, which is attributed to local meteorology. Somewhat similar depletion of water may be present in the 5-micron bright regions of Saturn also. The supersolar abundances of heavy elements, particularly C and S in Jupiter's atmosphere and C in Saturn's, as well as the progressive increase of C from Jupiter to Saturn and beyond, tend to support the icy planetesimal model of the formation of the giant planets and their atmospheres. However, much work remains to be done, especially in the area of laboratory studies, including identification of possible new microwave absorbers, and modelling, in order to resolve the controversy surrounding the large discrepancy between Jupiter's global ammonia abundance, hence the nitrogen elemental ratio, derived from the earth-based microwave observations and that inferred from the analysis of the Galileo probe-orbiter radio attenuation data for the hotspot. We look forward to the observations from Cassini-Huygens spacecraft which are expected to result not only in a rich harvest of information for Saturn, but a better understanding of the formation of the giant planets and their atmospheres when these data are combined with those that exist for Jupiter.
Collapse
Affiliation(s)
- S K Atreya
- Department of Atmospheric, Oceanic and Space Sciences, The University of Michigan, Ann Arbor 48109-2143, USA.
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Trauger JT, Clarke JT, Ballester GE, Evans RW, Burrows CJ, Crisp D, Gallagher JS, Griffiths RE, Hester JJ, Hoessel JG, Holtzman JA, Krist JE, Mould JR, Sahai R, Scowen PA, Stapelfeldt KR, Watson AM. Saturn's hydrogen aurora: Wide field and planetary camera 2 imaging from the Hubble Space Telescope. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98je01324] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
23
|
Feuchtgruber H, Lellouch E, de Graauw T, Bézard B, Encrenaz T, Griffin M. External supply of oxygen to the atmospheres of the giant planets. Nature 1997; 389:159-62. [PMID: 9296492 DOI: 10.1038/38236] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The atmospheres of the giant planets are reducing, being mainly composed of hydrogen, helium and methane. But the rings and icy satellites that surround these planets, together with the flux of interplanetary dust, could act as important sources of oxygen, which would be delivered to the atmospheres mainly in the form of water ice or silicate dust. Here we report the detection, by infrared spectroscopy, of gaseous H2O in the upper atmospheres of Saturn, Uranus and Neptune. The implied H2O column densities are 1.5 x 10(15), 9 x 10(13) and 3 x 10(14) molecules cm(-2) respectively. CO2 in comparable amounts was also detected in the atmospheres of Saturn and Neptune. These observations can be accounted for by external fluxes of 10(5)-10(7) H2O molecules cm(-2) s(-1) and subsequent chemical processing in the atmospheres. The presence of gaseous water and infalling dust will affect the photochemistry, energy budget and ionospheric properties of these atmospheres. Moreover, our findings may help to constrain the injection rate and possible activity of distant icy objects in the Solar System.
Collapse
Affiliation(s)
- H Feuchtgruber
- Max-Planck Institut für Extraterrestrische Physik, Garching, Germany
| | | | | | | | | | | |
Collapse
|
24
|
Seiff A, Kirk DB, Knight TCD, Young LA, Milos FS, Venkatapathy E, Mihalov JD, Blanchard RC, Young RE, Schubert G. Thermal Structure of Jupiter's Upper Atmosphere Derived from the Galileo Probe. Science 1997; 276:102-4. [PMID: 9082977 DOI: 10.1126/science.276.5309.102] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Temperatures in Jupiter's atmosphere derived from Galileo Probe deceleration data increase from 109 kelvin at the 175-millibar level to 900 ± 40 kelvin at 1 nanobar, consistent with Voyager remote sensing data. Wavelike oscillations are present at all levels. Vertical wavelengths are 10 to 25 kilometers in the deep isothermal layer, which extends from 12 to 0.003 millibars. Above the 0.003-millibar level, only 90- to 270- kilometer vertical wavelengths survive, suggesting dissipation of wave energy as the probable source of upper atmosphere heating.
Collapse
Affiliation(s)
- A Seiff
- A. Seiff, Department of Meteorology, San Jose State University Foundation and MS 245-1, Ames Research Center, Moffett Field, CA 94035, USA. D. B. Kirk, University of Oregon, 37465 Riverside Drive, Pleasant Hill, Oregon 97455, USA. T. C. D. Knight, 2370 S. Brentwood St., Lakewood, CO 80227, USA. L. A. Young, Center for Space Physics, Boston University, 725 Commonwealth Ave., Boston, Massachusetts 02215, USA. F. S. Milos, M.S. 234-1, Ames Research Center, NASA, Moffett Field, CA 94035, USA. E. Venkatapathy, Eloret Institute, MS 230-2, Ames Research Center, Moffett Field, CA 94035, USA. J. D. Mihalov and R. E. Young, MS 245-3, Ames Research Center, Moffett Field, CA 94035, USA. R. C. Blanchard, MS 408A, Langley Research Center, NASA, Hampton, VA 23681, USA. G. Schubert, Department of Earth and Space Sciences, University of California, Los Angeles, CA 90024, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Majeed T, McConnell JC. Voyager electron density measurements on Saturn: Analysis with a time dependent ionospheric model. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/96je00115] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
26
|
Yelle RV, Young LA, Vervack RJ, Young R, Pfister L, Sandel BR. Structure of Jupiter's upper atmosphere: Predictions for Galileo. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/95je03384] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
27
|
Jaffel LB, Leers V, Sandel BR. Dark Auroral Oval on Saturn Discovered in Hubble Space Telescope Ultraviolet Images. Science 1995; 269:951-3. [PMID: 17807729 DOI: 10.1126/science.269.5226.951] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Hubble Space Telescope ultraviolet images of Saturn obtained with the Faint Object Camera near 220 nanometers reveal a dark oval encircling the north magnetic pole of the planet. The opacity has an equivalent width of approximately 11 degrees in latitude and is centered around approximately 79 degrees N. The oval shape of the dark structure and its coincidence with the aurora detected by the Voyager Ultraviolet Spectrometer suggest that the aerosol formation is related to the auroral activity.
Collapse
|
28
|
|
29
|
|
30
|
Cheng AF, Waite JH. Corotation lag of Saturn's magnetosphere: Global ionospheric conductivities revisited. ACTA ACUST UNITED AC 1988. [DOI: 10.1029/ja093ia05p04107] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
31
|
Shemansky DE, Judge DL. Evidence for change in particle excitation of Jupiter's atmosphere 1968–1979. ACTA ACUST UNITED AC 1988. [DOI: 10.1029/ja093ia01p00021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
32
|
Clarke JT, Hudson MK, Yung YL. The excitation of the far ultraviolet electroglow emissions on Uranus, Saturn, and Jupiter. JOURNAL OF GEOPHYSICAL RESEARCH 1987; 92:15139-47. [PMID: 11542130 DOI: 10.1029/ja092ia13p15139] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We propose that the diffuse FUV emissions of H and H2 in excess of photoelectron excitation observed from the sunlit atmospheres of Uranus, Saturn, and Jupiter are produced by electric field acceleration of photoelectrons and ions locally in the upper atmospheres. This in situ acceleration is required to satisfy the many observational constraints on the altitude distribution, exciting particle energy, and total input energy requirements of the electroglow mechanism. We further suggest that a primary mechanism leading to this acceleration is an ionospheric dynamo, which is created in the same manner as the Earth's dynamo. The calculated altitude of charge separation by the neutral wind drag on ions across magnetic field lines is consistent with the observed peaks in electroglow emissions from the Voyager ultraviolet spectrometer limb scan data on both Saturn (near the homopause) and Uranus (just above the homopause). This dynamo action therefore appears to initiate the acceleration process, which must have the form of field-aligned potentials to accelerate the magnetized electrons. We propose that these field-aligned potentials are due to anomalous resistivity, which results from sufficiently high field-aligned currents in the ionosphere to generate plasma instabilities and therefore runaway electrons and ions above some critical lower initial energy. There are multiple candidate processes for inducing these currents, including polarization in the equivalent F regions and inner magnetospheric convection, and each of these processes should exhibit latitudinal structure. The acceleration of low-energy electrons in an H2 atmosphere preferentially results in FUV radiation and further ionization, whereas electron acceleration in a nitrogen/oxygen atmosphere such as the Earth's is dominated by elastic scattering and thus results in electric currents. Individual electron and proton collisions with H2 molecules will result in excitation, ionization, and heating, so that considerable enhancement of the ionospheric density and heating of the upper atmosphere will accompany the FUV emission.
Collapse
Affiliation(s)
- J T Clarke
- Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | | | | |
Collapse
|
33
|
|
34
|
Yelle RV, Sandel BR, Shemansky DE, Kumar S. Altitude variation of EUV emissions and evidence for proton precipitation at low latitudes in the Saturnian atmosphere. ACTA ACUST UNITED AC 1986. [DOI: 10.1029/ja091ia08p08756] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
35
|
|
36
|
Shemansky DE. An explanation for the H Ly α longitudinal asymmetry in the equatorial spectrum of Jupiter: An outcrop of paradoxical energy deposition in the exosphere. ACTA ACUST UNITED AC 1985. [DOI: 10.1029/ja090ia03p02673] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|