Uranus System: 27 Satellites, Rings 1 27 Uranian Satellites Distance Radius Mass Satellite (000 km) (km) (kg) Discoverer Date --------- -------- ------ ------- ---------- ----- Cordelia 50 13 ? Voyager 2 1986 Ophelia 54 16 ? Voyager 2 1986 Bianca 59 22 ? Voyager 2 1986 Cressida 62 33 ? Voyager 2 1986 Desdemona 63 29 ? Voyager 2 1986 Juliet 64 42 ? Voyager 2 1986 Portia 66 55 ? Voyager 2 1986 Rosalind 70 27 ? Voyager 2 1986 Cupid (2003U2) 75 6 ? Showalter 2003 Belinda 75 34 ? Voyager 2 1986 Perdita 76 40 ? Voyager 2 1986 Puck 86 77 ? Voyager 2 1985 Mab (2003U1) 98 8 ? Showalter 2003 Miranda 130 236 6.30e19 Kuiper 1948 Ariel 191 579 1.27e21 Lassell 1851 Umbriel 266 585 1.27e21 Lassell 1851 Titania 436 789 3.49e21 Herschel 1787 Oberon 583 761 3.03e21 Herschel 1787 Francisco 4281 6 ? Holman 2003 Caliban 7169 40 ? Gladman 1997 Stephano 7948 15 ? Gladman 1999 Trinculo 8578 5 ? Holman 2001 Sycorax 12213 80 ? Nicholson 1997 Margaret 14689 6 ? Sheppard 2003 Prospero 16568 20 ? Holman 1999 Setebos 17681 20 ? Kavelaars 1999 Ferdinand 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 Epimetheus 151 57 5.60e17 Walker 1980 Puck 86 77 ? Voyager 2 1985 Janus 151 89 2.01e18 Dollfus 1966 Phoebe 12952 110 4.00e18 Pickering 1898 Hyperion 1481 143 1.77e19 Bond 1848 Mimas 186 196 3.80e19 Herschel 1789 Miranda 130 236 6.30e19 Kuiper 1948 Enceladus 238 260 8.40e19 Herschel 1789 Tethys 295 530 7.55e20 Cassini 1684 Dione 377 560 1.05e21 Cassini 1684 Ariel 191 579 1.27e21 Lassell 1851 Umbriel 266 585 1.27e21 Lassell 1851 Iapetus 3561 730 1.88e21 Cassini 1671 Oberon 583 761 3.03e21 Herschel 1787 Rhea 527 765 2.49e21 Cassini 1672 Titania 436 789 3.49e21 Herschel 1787 Titan 1222 2575 1.35e23 Huygens 1655 4 Uranian Satellites Distance Radius Mass Density Inc. Ecc. Albedo(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 Densities (T.V. Johnson) Density vs Size Porosity effects Compression effects 2.50 Jupiter System 100 % Ice 2.00 60 % Ice 1.50 Saturn System Uranus 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 Pluto Triton Ganymede, 100 % Ice 2.00 Callisto 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 tectonics, 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 Gertrude and Ursula = pit craters? system of ridges and extensional tectonics only example of compressional tectonics much stronger (wavelength dependent) opposition effect than other surfaces in Solar System – 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 graben 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 planet and satellite formation? 2. How long did it take the gas giant 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? Volatiles 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 Earth? 9. Why did the terrestrial planets 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 = Equinox 1944 = N Summer 1965 = Equinox 1986 = N Winter 2007 = Equinox 2028 = N Summer 2049 = Equinox 25 26 Uranus System: 27 Satellites, Rings 27.