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Uranus System: 27 Satellites, Rings

1 27 Uranian Satellites

Distance Radius Satellite (000 km) (km) (kg) Discoverer Date ------ 50 13 ? 1986 54 16 ? Voyager 2 1986 59 22 ? Voyager 2 1986 62 33 ? Voyager 2 1986 63 29 ? Voyager 2 1986 64 42 ? Voyager 2 1986 66 55 ? Voyager 2 1986 70 27 ? Voyager 2 1986 (2003U2) 75 6 ? Showalter 2003 75 34 ? Voyager 2 1986 76 40 ? Voyager 2 1986 86 77 ? Voyager 2 1985 (2003U1) 98 8 ? Showalter 2003 130 236 6.30e19 Kuiper 1948 191 579 1.27e21 Lassell 1851 266 585 1.27e21 Lassell 1851 436 789 3.49e21 Herschel 1787 583 761 3.03e21 Herschel 1787 4281 6 ? Holman 2003 7169 40 ? Gladman 1997 7948 15 ? Gladman 1999 8578 5 ? Holman 2001 12213 80 ? Nicholson 1997 14689 6 ? Sheppard 2003 16568 20 ? Holman 1999 17681 20 ? Kavelaars 1999 21000 6 ? Sheppard 2003

2 Uranian Satellites

Oberon Titania Umbriel

Miranda Ariel

Puck

3 Uranian and Saturnian Satellites Distance Radius Mass Satellite (000 km) (km) (kg) Discoverer Date 151 57 5.60e17 Walker 1980 Puck 86 77 ? Voyager 2 1985 Janus 151 89 2.01e18 Dollfus 1966 12952 110 4.00e18 Pickering 1898 1481 143 1.77e19 Bond 1848 186 196 3.80e19 Herschel 1789 Miranda 130 236 6.30e19 Kuiper 1948 238 260 8.40e19 Herschel 1789 295 530 7.55e20 Cassini 1684 377 560 1.05e21 Cassini 1684 Ariel 191 579 1.27e21 Lassell 1851 Umbriel 266 585 1.27e21 Lassell 1851 3561 730 1.88e21 Cassini 1671 Oberon 583 761 3.03e21 Herschel 1787 527 765 2.49e21 Cassini 1672 Titania 436 789 3.49e21 Herschel 1787 1222 2575 1.35e23 Huygens 1655 4 Uranian Satellites

Distance Radius Mass Inc. Ecc. (max) Satellite (000 km) (km) (kg) (kg/m3)

Miranda 130 236 6.30e19 1200 4.22° 0.0027 0.27(0.45) Ariel 191 579 1.27e21 1670 0.31° 0.0034 0.35(0.55) Umbriel 266 585 1.27e21 1400 0.36° 0.0050 0.19(0.49) Titania 436 789 3.49e21 1710 0.14° 0.0022 0.28(0.31) Oberon 583 761 3.03e21 1630 0.10° 0.0008 0.25(0.34)

5 Satellite (T.V. Johnson)

Density vs Size Porosity effects Compression effects 2.50 System 100 % 2.00 60 % Ice 1.50 System System 1.00 "KBO's" Saturn Co-Orbitals 0.50 Phoebe Density, kg/m^3 X kg/m^3 10^-3 Density, 0.00 10 100 1000 10000 Radius, km

6 Satellite Densities (T.V. Johnson)

Density vs Size

2.50 Jupiter System , 100 % Ice 2.00 Phoebe Titania Titan 60 % Ice Ariel Oberon 1.50 Dione Saturn System Umbriel Miranda Rhea Uranus System Mimas 1.00 Enceladus. "KBO's" Tethys Iapetus Saturn Co-Orbitals 0.50 Phoebe Density, kg/m^3 X 10^-3 0.00 10 100 1000 10000 Radius, km

7 Oberon, R = 761 km best imaging 12 km/lp heavily cratered, no evidence for viscous relaxation 11-km-high, 45-km-wide mountain (central peak? (no crater rim) extensional , multiple generations of scarps and canyons youngest unit = dark terrain, cryovolcanic flooding of crater floors and tectonically controlled lows

8 Oberon, R = 761 km best imaging 12 km/lp spherical to limits of resolution (hydrostatic equilibrium a-c < 1 km) topographic features up to 11 km

9 Titania, R = 789 km best imaging 6.8 km/lp less albedo variation, no dark deposits, fewer bright-ejecta craters heavily cratered, deficient in largest (>100 km) craters compared to Oberon; degradation of old craters primarily tectonic

10 Titania, R = 789 km craters and = pit craters? system of ridges and extensional tectonics only example of compressional tectonics much stronger (wavelength dependent) opposition effect than other surfaces in – open regolith texture?

11 Titania, R = 789 km best imaging 6.8 km/lp spherical to limits of resolution (hydrostatic equilibrium a-c < 1 km) topographic features up to 4 km

12 Umbriel, R = 585 km best imaging ~10 km/lp heavily cratered, distribution similar to Oberon dark, low-contrast surface; two very bright areas extensional tectonics, canyons, horst and terrain, ~50 km wide, 3-4 km deep both dark and light cryovolcanism?

13 Umbriel, R = 585 km best imaging 10 km/lp spherical to limits of resolution (hydrostatic equilibrium a-c ~ 2 km) topographic features up to 6 km

14 Ariel, R = 579 km best imaging 1.3 km/lp deficient in 100-km craters, comparatively low crater density possible population of degraded or buried ancient craters shallow – intrusive or extrusive cryovolcanism or relaxation? high-albedo ejecta (related to flow material?)

15 Ariel, R = 579 km extensional tectonics graben tilted blocks cryovolcanic units convex valley floor units with marginal troughs 1-2 km deep (extend past ends of canyons) flows override craters 100s m to kms thick multiple stages of tectonism and volcanism are interleaved, causally related?

16 Ariel, R = 579 km best resolution ~300 m triaxial shape consistent with hydrostatic equilibrium (581x578x578) topographic features up to 4 km

17 Ariel, R = 579 km

18 Miranda, R = 236 km best resolution ~300 m heavily cratered terrain, some fresh dark-ray craters tectonic deformation, multiple styles of canyons either subdued or fresh, little intermediate degradation mantling event?

19 Miranda, R = 236 km coronae differ substantially Arden (oldest) bounded by canyon, some albedo variation, portion sits lower than surroundings, impact origin? Inverness lower than surrounding terrain, albedo contrast Elsinore (youngest) stands generally higher, islands of cratered terrain, uniform albedo

20 Miranda, R = 236 km best resolution ~300 m triaxial shape consistent with hydrostatic equilibrium (240x234x233) topographic features up to 10-15 km

21 Miranda, R = 236 km

22 Major issues to be addressed Satellite formation and evolution • Especially the dynamical and geologic histories that led to the observed diversity and the role played by tidal dissipation • Implications of regular satellite system in the context of Uranus’ obliquity • Cratering history and implications for projectile populations Composition, nature of the dark material(s) **At 19 AU, the Uranian system provides an important data point regarding the distribution and origins of organic and volatile materials Interior structures, degree of differentiation, past or present liquid water at depth or on surfaces **Strong evidence for cryovolcanism in the form of viscous 23 extrusive flows Questions from previous decadal survey The First Billion Years of Solar System History: 1. What processes marked the initial stages of and satellite formation? 2. How long did it take the Jupiter to form, and how was the formation of the ice giants different from that of the gas giants? 3. What was the rate of decrease in the impactor flux throughout the solar system, and how did it affect the timing of the emergence of life? and Organics; The Stuff of Life. 4. What is the history of volatile material, especially water, in our Solar System? 5. What is the nature and history of organic material in our Solar System? 6. What planetary processes affect the evolution of volatiles on planetary bodies? The Origin and Evolution of Habitable Worlds. 7. Where are the habitable zones for life in our Solar System, and what are the planetary processes responsible for producing and sustaining habitable worlds? 8. Does (or did) life exist beyond the ? 9. Why did the terrestrial diverge so dramatically in their evolution? 10. What hazards do Solar System objects present to Earth's biosphere? Processes; How Planets Work. 11. How do the processes that shape the contemporary character of planetary bodies operate and interact? 12. What does our solar system tell us about other solar systems, and vice versa? 24 Uranian Seasons

1902 = N Winter 1923 = 1944 = N Summer 1965 = Equinox 1986 = N Winter 2007 = Equinox 2028 = N Summer 2049 = Equinox

25 26 Uranus System: 27 Satellites, Rings

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