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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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Veverka J, Thomas P, Helfenstein P, Brown RH, Johnson TV. Satellites of Uranus: Disk‐integrated photometry from Voyager imaging observations. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p14895] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [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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Thomas PC, Veverka J, Helfenstein P, Brown RH, Johnson TV. Titania's opposition effect: Analysis of Voyager observations. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p14911] [Citation(s) in RCA: 15] [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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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]
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Ockert ME, Cuzzi JN, Porco CC, Johnson TV. Uranian ring photometry: Results from Voyager 2. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/ja092ia13p14969] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Smith BA, Soderblom LA, Beebe R, Bliss D, Boyce JM, Brahic A, Briggs GA, Brown RH, Collins SA, Cook AF, Croft SK, Cuzzi JN, Danielson GE, Davies ME, Dowling TE, Godfrey D, Hansen CJ, Harris C, Hunt GE, Ingersoll AP, Johnson TV, Krauss RJ, Masursky H, Morrison D, Owen T, Plescia JB, Pollack JB, Porco CC, Rages K, Sagan C, Shoemaker EM, Sromovsky LA, Stoker C, Strom RG, Suomi VE, Synnott SP, Terrile RJ, Thomas P, Thompson WR, Veverka J. Voyager 2 in the uranian system: imaging science results. Science 2010; 233:43-64. [PMID: 17812889 DOI: 10.1126/science.233.4759.43] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Voyager 2 images of the southern hemisphere of Uranus indicate that submicrometersize haze particles and particles of a methane condensation cloud produce faint patterns in the atmosphere. The alignment of the cloud bands is similar to that of bands on Jupiter and Saturn, but the zonal winds are nearly opposite. At mid-latitudes (-70 degrees to -27 degrees ), where winds were measured, the atmosphere rotates faster than the magnetic field; however, the rotation rate of the atmosphere decreases toward the equator, so that the two probably corotate at about -20 degrees . Voyager images confirm the extremely low albedo of the ring particles. High phase angle images reveal on the order of 10(2) new ringlike features of very low optical depth and relatively high dust abundance interspersed within the main rings, as well as a broad, diffuse, low optical depth ring just inside the main rings system. Nine of the newly discovered small satellites (40 to 165 kilometers in diameter) orbit between the rings and Miranda; the tenth is within the ring system. Two of these small objects may gravitationally confine the e ring. Oberon and Umbriel have heavily cratered surfaces resembling the ancient cratered highlands of Earth's moon, although Umbriel is almost completely covered with uniform dark material, which perhaps indicates some ongoing process. Titania and Ariel show crater populations different from those on Oberon and Umbriel; these were probably generated by collisions with debris confined to their orbits. Titania and Ariel also show many extensional fault systems; Ariel shows strong evidence for the presence of extrusive material. About halfof Miranda's surface is relatively bland, old, cratered terrain. The remainder comprises three large regions of younger terrain, each rectangular to ovoid in plan, that display complex sets of parallel and intersecting scarps and ridges as well as numerous outcrops of bright and dark materials, perhaps suggesting some exotic composition.
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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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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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Aslaksen TK, Havnes O. The effects of electrostatic forces and random velocities on dust ring thickness profiles in rings with a dust size distribution. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92ja01402] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Murray CD, Thompson RP. Orbits of shepherd satellites deduced from the structure of the rings of Uranus. Nature 1990. [DOI: 10.1038/348499a0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Smith BA, Soderblom LA, Banfield D, Barnet C, Basilevsky AT, Beebe RF, Bollinger K, Boyce JM, Brahic A, Briggs GA, Brown RH, Chyba C, Collins SA, Colvin T, Cook AF, Crisp D, Croft SK, Cruikshank D, Cuzzi JN, Danielson GE, Davies ME, De Jong E, Dones L, Godfrey D, Goguen J, Grenier I, Haemmerle VR, Hammel H, Hansen CJ, Helfenstein CP, Howell C, Hunt GE, Ingersoll AP, Johnson TV, Kargel J, Kirk R, Kuehn DI, Limaye S, Masursky H, McEwen A, Morrison D, Owen T, Owen W, Pollack JB, Porco CC, Rages K, Rogers P, Rudy D, Sagan C, Schwartz J, Shoemaker EM, Showalter M, Sicardy B, Simonelli D, Spencer J, Sromovsky LA, Stoker C, Strom RG, Suomi VE, Synott SP, Terrile RJ, Thomas P, Thompson WR, Verbiscer A, Veverka J. Voyager 2 at Neptune: Imaging Science Results. Science 1989; 246:1422-49. [PMID: 17755997 DOI: 10.1126/science.246.4936.1422] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Voyager 2 images of Neptune reveal a windy planet characterized by bright clouds of methane ice suspended in an exceptionally clear atmosphere above a lower deck of hydrogen sulfide or ammonia ices. Neptune's atmosphere is dominated by a large anticyclonic storm system that has been named the Great Dark Spot (GDS). About the same size as Earth in extent, the GDS bears both many similarities and some differences to the Great Red Spot of Jupiter. Neptune's zonal wind profile is remarkably similar to that of Uranus. Neptune has three major rings at radii of 42,000, 53,000, and 63,000 kilometers. The outer ring contains three higher density arc-like segments that were apparently responsible for most of the ground-based occultation events observed during the current decade. Like the rings of Uranus, the Neptune rings are composed of very dark material; unlike that of Uranus, the Neptune system is very dusty. Six new regular satellites were found, with dark surfaces and radii ranging from 200 to 25 kilometers. All lie inside the orbit of Triton and the inner four are located within the ring system. Triton is seen to be a differentiated body, with a radius of 1350 kilometers and a density of 2.1 grams per cubic centimeter; it exhibits clear evidence of early episodes of surface melting. A now rigid crust of what is probably water ice is overlain with a brilliant coating of nitrogen frost, slightly darkened and reddened with organic polymer material. Streaks of organic polymer suggest seasonal winds strong enough to move particles of micrometer size or larger, once they become airborne. At least two active plumes were seen, carrying dark material 8 kilometers above the surface before being transported downstream by high level winds. The plumes may be driven by solar heating and the subsequent violent vaporization of subsurface nitrogen.
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Lane AL, West RA, Hord CW, Nelson RM, Simmons KE, Pryor WR, Eposito LW, Horn LJ, Wallis BD, Buratti BJ, Brophy TG, Yanamandra-Fisher P, Colwell JE, Bliss DA, Mayo MJ, Smythe WD. Photometry from Voyager 2: Initial Results from the Neptunian Atmosphere, Satellites, and Rings. Science 1989; 246:1450-4. [PMID: 17755998 DOI: 10.1126/science.246.4936.1450] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Voyager photopolarimeter successfully accomplished its objectives for the Neptune encounter, performing measurements on the planet, several of its satellites, and its ring system. A photometric map of Neptune at 0.26 micrometer (microm) shows the planet to be bland, with no obvious contrast features. No polar haze was observed. At 0.75 microm, contrast features are observed, with the Great Dark Spot appearing as a low-albedo region and the bright companion as being substantially brighter than its surroundings, implying it to be at a higher altitude than the Great Dark Spot. Triton's linear phase coefficients of 0.011 magnitudes per degree at 0.26 microm and 0.013 magnitudes per degree at 0.75 microm are consistent with a solid-surface object possessing high reflectivity. Preliminary geometric albedos for Triton, Nereid, and 1989N2 were obtained at 0.26 and 0.75 microm. Triton's rotational phase curve shows evidence of two major compositional units on its surface. A single stellar occultation of the Neptune ring system elucidated an internal structure in 1989N1R, in the approximately 50-kilometer region of modest optical depth. 1989N2R may have been detected. The deficiency of material in the Neptune ring system, when compared to Uranus', may imply the lack of a "recent" moon-shattering event.
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