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Cohen IJ, Smith EJ, Clark GB, Turner DL, Ellison DH, Clare B, Regoli LH, Kollmann P, Gallagher DT, Holtzman GA, Likar JJ, Morizono T, Shannon M, Vodusek KS. Plasma Environment, Radiation, Structure, and Evolution of the Uranian System (PERSEUS): A Dedicated Orbiter Mission Concept to Study Space Physics at Uranus. SPACE SCIENCE REVIEWS 2023; 219:65. [PMID: 37869526 PMCID: PMC10587260 DOI: 10.1007/s11214-023-01013-6] [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: 07/14/2023] [Accepted: 10/05/2023] [Indexed: 10/24/2023]
Abstract
The Plasma Environment, Radiation, Structure, and Evolution of the Uranian System (PERSEUS) mission concept defines the feasibility and potential scope of a dedicated, standalone Heliophysics orbiter mission to study multiple space physics science objectives at Uranus. Uranus's complex and dynamic magnetosphere presents a unique laboratory to study magnetospheric physics as well as its coupling to the solar wind and the planet's atmosphere, satellites, and rings. From the planet's tilted and offset, rapidly-rotating non-dipolar magnetic field to its seasonally-extreme interactions with the solar wind to its unexpectedly intense electron radiation belts, Uranus hosts a range of outstanding and compelling mysteries relevant to the space physics community. While the exploration of planets other than Earth has largely fallen within the purview of NASA's Planetary Science Division, many targets, like Uranus, also hold immense scientific value and interest to NASA's Heliophysics Division. Exploring and understanding Uranus's magnetosphere is critical to make fundamental gains in magnetospheric physics and the understanding of potential exoplanetary systems and to test the validity of our knowledge of magnetospheric dynamics, moon-magnetosphere interactions, magnetosphere-ionosphere coupling, and solar wind-planetary coupling. The PERSEUS mission concept study, currently at Concept Maturity Level (CML) 4, comprises a feasible payload that provides closure to a range of space physics science objectives in a reliable and mature spacecraft and mission design architecture. The mission is able to close using only a single Mod-1 Next-Generation Radioisotope Thermoelectric Generator (NG-RTG) by leveraging a concept of operations that relies of a significant hibernation mode for a large portion of its 22-day orbit.
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Affiliation(s)
- Ian J Cohen
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Evan J Smith
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - George B Clark
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Drew L Turner
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Donald H Ellison
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Ben Clare
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Leonardo H Regoli
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Peter Kollmann
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | | | - G Allan Holtzman
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Justin J Likar
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Takeshi Morizono
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Matthew Shannon
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 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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Moore L, Melin H, O'Donoghue J, Stallard TS, Moses JI, Galand M, Miller S, Schmidt CA. Modelling H 3+ in planetary atmospheres: effects of vertical gradients on observed quantities. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20190067. [PMID: 31378180 PMCID: PMC6710898 DOI: 10.1098/rsta.2019.0067] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/07/2019] [Indexed: 05/20/2023]
Abstract
Since its detection in the aurorae of Jupiter approximately 30 years ago, the H3+ ion has served as an invaluable probe of giant planet upper atmospheres. However, the vast majority of monitoring of planetary H3+ radiation has followed from observations that rely on deriving parameters from column-integrated paths through the emitting layer. Here, we investigate the effects of density and temperature gradients along such paths on the measured H3+ spectrum and its resulting interpretation. In a non-isothermal atmosphere, H3+ column densities retrieved from such observations are found to represent a lower limit, reduced by 20% or more from the true atmospheric value. Global simulations of Uranus' ionosphere reveal that measured H3+ temperature variations are often attributable to well-understood solar zenith angle effects rather than indications of real atmospheric variability. Finally, based on these insights, a preliminary method of deriving vertical temperature structure is demonstrated at Jupiter using model reproductions of electron density and H3+ measurements. The sheer diversity and uncertainty of conditions in planetary atmospheres prohibits this work from providing blanket quantitative correction factors; nonetheless, we illustrate a few simple ways in which the already formidable utility of H3+ observations in understanding planetary atmospheres can be enhanced. This article is part of a discussion meeting issue 'Advances in hydrogen molecular ions: H3+, H5+ and beyond'.
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Affiliation(s)
- L. Moore
- Boston University, Boston, MA, USA
| | - H. Melin
- University of Leicester, Leicester, UK
| | - J. O'Donoghue
- NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | | | - M. Galand
- Department of Physics, Imperial College London, London, UK
| | - S. Miller
- University College London, London, UK
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Moses JI, Fletcher LN, Greathouse TK, Orton GS, Hue V. Seasonal Stratospheric Photochemistry on Uranus and Neptune. ICARUS 2018; 307:124-145. [PMID: 30842687 PMCID: PMC6398965 DOI: 10.1016/j.icarus.2018.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A time-variable 1D photochemical model is used to study the distribution of stratospheric hydrocarbons as a function of altitude, latitude, and season on Uranus and Neptune. The results for Neptune indicate that in the absence of stratospheric circulation or other meridional transport processes, the hydrocarbon abundances exhibit strong seasonal and meridional variations in the upper stratosphere, but that these variations become increasingly damped with depth due to increasing dynamical and chemical time scales. At high altitudes, hydrocarbon mixing ratios are typically largest where the solar insolation is the greatest, leading to strong hemispheric dichotomies between the summer-to-fall hemisphere and winter-to-spring hemisphere. At mbar pressures and deeper, slower chemistry and diffusion lead to latitude variations that become more symmetric about the equator. On Uranus, the stagnant, poorly mixed stratosphere confines methane and its photochemical products to higher pressures, where chemistry and diffusion time scales remain large. Seasonal variations in hydrocarbons are therefore predicted to be more muted on Uranus, despite the planet's very large obliquity. Radiative-transfer simulations demonstrate that latitude variations in hydrocarbons on both planets are potentially observable with future JWST mid-infrared spectral imaging. Our seasonal model predictions for Neptune compare well with retrieved C2H2 and C2H6 abundances from spatially resolved ground-based observations (no such observations currently exist for Uranus), suggesting that stratospheric circulation - which was not included in these models - may have little influence on the large-scale meridional hydrocarbon distributions on Neptune, unlike the situation on Jupiter and Saturn.
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Affiliation(s)
- Julianne I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - Leigh N Fletcher
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | | | - Glenn S Orton
- Jet Propulsion Laboratory, MS 183-501, Pasadena, CA 91109, USA
| | - Vincent Hue
- Southwest Research Institute, San Antonio, TX 78228, USA
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7
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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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8
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Fegley B. Properties and Composition of the Terrestrial Oceans and of the Atmospheres of the Earth and Other Planets. AGU REFERENCE SHELF 2013. [DOI: 10.1029/rf001p0320] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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9
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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]
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Pollack JB, Rages K, Pope SK, Tomasko MG, Romani PN, Atreya SK. Nature of the stratospheric haze on Uranus: Evidence for condensed hydrocarbons. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p15037] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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11
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Herbert F. The Uranian corona as a charge exchange cascade of plasma sheet protons. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/92ja02735] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Rizk B, Hunten DM, Engel S. Effects of size-dependent emissivity on maximum temperatures during micrometeorite entry. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/90ja01998] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Singhal RP, Bhardwaj A. Monte Carlo simulation of photoelectron energization in parallel electric fields: Electroglow on Uranus. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/90ja02749] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lindal GF, Lyons JR, Sweetnam DN, Eshleman VR, Hinson DP, Tyler GL. The atmosphere of Uranus: Results of radio occultation measurements with Voyager 2. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p14987] [Citation(s) in RCA: 252] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Broadfoot AL, Atreya SK, Bertaux JL, Blamont JE, Dessler AJ, Donahue TM, Forrester WT, Hall DT, Herbert F, Holberg JB, Hunter DM, Krasnopolsky VA, Linick S, Lunine JI, McConnell JC, Moos HW, Sandel BR, Schneider NM, Shemansky DE, Smith GR, Strobel DF, Yelle RV. Ultraviolet spectrometer observations of neptune and triton. Science 2010; 246:1459-66. [PMID: 17756000 DOI: 10.1126/science.246.4936.1459] [Citation(s) in RCA: 286] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Results from the occultation of the sun by Neptune imply a temperature of 750 +/- 150 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane, acetylene, and ethane at lower levels. The ultraviolet spectrum of the sunlit atmosphere of Neptune resembles the spectra of the Jupiter, Saturn, and Uranus atmospheres in that it is dominated by the emissions of H Lyman alpha (340 +/- 20 rayleighs) and molecular hydrogen. The extreme ultraviolet emissions in the range from 800 to 1100 angstroms at the four planets visited by Voyager scale approximately as the inverse square of their heliocentric distances. Weak auroral emissions have been tentatively identified on the night side of Neptune. Airglow and occultation observations of Triton's atmosphere show that it is composed mainly of molecular nitrogen, with a trace of methane near the surface. The temperature of Triton's upper atmosphere is 95 +/- 5 kelvins, and the surface pressure is roughly 14 microbars.
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Affiliation(s)
- Floyd Herbert
- Lunar and Planetary Laboratory; University of Arizona; Tucson Arizona USA
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17
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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
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18
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Burns JA, Hamilton DP, Showalter MR. Dusty Rings and Circumplanetary Dust: Observations and Simple Physics. ASTRONOMY AND ASTROPHYSICS LIBRARY 2001. [DOI: 10.1007/978-3-642-56428-4_13] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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19
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Lee AYT, Yung YL, Moses J. Photochemical modeling of CH3abundances in the outer solar system. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001186] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Application of a radiative-convective equilibrium model to the thermal structure of Uranus' atmosphere evaluates the role of hazes in the planet's stratospheric energy budget and places a lower limit on the internal energy flux. The model is constrained by Voyager and post-Voyager observations of the vertical aerosol and radiative active gas profiles. Our baseline model generally reproduces the observed tropospheric and stratospheric temperature profile. However, as in past studies, the model stratosphere from about 10(-3) to 10(-1) bar is too cold. We find that the observed stratospheric hazes do not warm this region appreciably and that any postulated hazes capable of warming the stratosphere sufficiently are inconsistent with Voyager and ground-based constraints. We explore the roles played by the stratospheric methane abundance, the H2 pressure-induced opacity, photochemical hazes, and C2H2, and C2H6 in controlling the temperature structure in this region. Assuming a vertical methane abundance profile consistent with that found by the Voyager UVS occultation observations, the model upper stratosphere, from 10 to 100 microbar, is also too cold. Radiation in the 7.8-micrometers band from a small abundance of hot methane in the lower thermosphere absorbed in this region can warm the atmosphere and bring models into closer agreement with observations. Finally, we find that internal heat fluxes < or approximately 60 erg cm-2 sec-1 are inconsistent with the observed tropospheric temperature profile.
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Affiliation(s)
- M S Marley
- Department of Astronomy, New Mexico State University, Las Cruces 88003, USA.
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22
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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]
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23
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Herbert F, Sandel BR. The Uranian aurora and its relationship to the magnetosphere. ACTA ACUST UNITED AC 1994. [DOI: 10.1029/93ja02673] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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25
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Smith PL, Yoshino K, Parkinson WH, Ito K, Stark G. High-resolution, VUV (147–201 nm) photoabsorption cross sections for C2H2at 195 and 295 K. ACTA ACUST UNITED AC 1991. [DOI: 10.1029/91je01739] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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Khare BN, Sagan C, Thompson WR, Arakawa ET, Votaw P. Solid hydrocarbon aerosols produced in simulated Uranian and Neptunian stratospheres. JOURNAL OF GEOPHYSICAL RESEARCH 1987; 92:15067-82. [PMID: 11542128 DOI: 10.1029/ja092ia13p15067] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Optical constants n and k are measured for thin hydrocarbon films produced from charged particles (RF plasma) irradiation of (1) 100% CH4; (2) 7% CH4, 93% H2; (3) 0.5% CH4, 99.5% H2; (4) 0.0002% CH4, 99.3% H2 (with impurities); and (5) 3 to 25% CH4, 25% He, remainder H2--all at submillibar pressures. In all experiments, yellow to deep brown-red solid products are synthesized which are hypothesized to be, at least in part, the unidentified visible and near-UV chromophores in the stratospheres of Uranus and Neptune. Results for experiments 2, 3, and 4 are in good mutual accord, but are significantly different from experiments 1 and 5. He in the precursor gases affects the product composition. Typical solid products for experiments 5 show, at 0.55 micrometer wavelength, n = 1.60 +/- 0.05, 3 x 10(-2) > or = k > or = 3 x 10(-3), and [C/H] approximately equal to 0.7. These results are, for n and k respectively, consistent with and in excellent agreement with those derived from high phase angle Voyager 2 photometry of Uranus (Pollack et al., this issue). Aerosols produced directly from the atmosphere by precipitating magnetospheric charged particles may be competitive with those produced by UV and charged particle irradiation of simple hydrocarbon condensates. The optical and chemical properties of aerosols in the Uranian and Neptunian atmospheres may evolve toward higher values of n and k and higher carbon content as the particles sediment through changing radiation and thermal environments.
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Affiliation(s)
- B N Khare
- Laboratory for Planetary Studies, Cornell University, Ithaca, New York, USA
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