Uranus System: 27 Satellites, Rings

Transcription

1 Uranus System: 27 Satellites, Rings 1

2 27 Uranian Satellites Distance Radius Mass Satellite (000 km) (km) (kg) Discoverer Date Cordelia 50 13? Voyager Ophelia 54 16? Voyager Bianca 59 22? Voyager Cressida 62 33? Voyager Desdemona 63 29? Voyager Juliet 64 42? Voyager Portia 66 55? Voyager Rosalind 70 27? Voyager Cupid (2003U2) 75 6? Showalter 2003 Belinda 75 34? Voyager Perdita 76 40? Voyager Puck 86 77? Voyager Mab (2003U1) 98 8? Showalter 2003 Miranda e19 Kuiper 1948 Ariel e21 Lassell 1851 Umbriel e21 Lassell 1851 Titania e21 Herschel 1787 Oberon e21 Herschel 1787 Francisco ? Holman 2003 Caliban ? Gladman 1997 Stephano ? Gladman 1999 Trinculo ? Holman 2001 Sycorax ? Nicholson 1997 Margaret ? Sheppard 2003 Prospero ? Holman 1999 Setebos ? Kavelaars 1999 Ferdinand ? Sheppard

3 Uranian Satellites Umbriel Oberon Titania Ariel Miranda Puck 3

4 Uranian and Saturnian Satellites Distance Radius Mass Satellite (000 km) (km) (kg) Discoverer Date Epimetheus e17 Walker 1980 Puck 86 77? Voyager Janus e18 Dollfus 1966 Phoebe e18 Pickering 1898 Hyperion e19 Bond 1848 Mimas e19 Herschel 1789 Miranda e19 Kuiper 1948 Enceladus e19 Herschel 1789 Tethys e20 Cassini 1684 Dione e21 Cassini 1684 Ariel e21 Lassell 1851 Umbriel e21 Lassell 1851 Iapetus e21 Cassini 1671 Oberon e21 Herschel 1787 Rhea e21 Cassini 1672 Titania e21 Herschel 1787 Titan e23 Huygens

5 Uranian Satellites Distance Radius Mass Density Inc. Ecc. Albedo(max) Satellite (000 km) (km) (kg) (kg/m 3 ) Miranda e (0.45) Ariel e (0.55) Umbriel e (0.49) Titania e (0.31) Oberon e (0.34) 5

6 Satellite Densities (T.V. Johnson) Density vs Size 2.50 Porosity effects Compression effects Jupiter System Density, kg/m^3 X 10^ % Ice 60 % Ice Saturn System Uranus System "KBO's" Saturn Co-Orbitals Phoebe Radius, km 6

7 Satellite Densities (T.V. Johnson) Density vs Size Density, kg/m^3 X 10^ Pluto Triton Phoebe Titania Ariel Oberon Dione Umbriel Miranda Rhea Mimas Enceladus. Tethys Iapetus Ganymede, Callisto Titan Jupiter System 100 % Ice 60 % Ice Saturn System Uranus System "KBO's" Saturn Co-Orbitals Phoebe Radius, km 7

8 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

9 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

10 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

11 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

12 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

13 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

14 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

15 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

16 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

17 Ariel, R = 579 km best resolution ~300 m triaxial shape consistent with hydrostatic equilibrium (581x578x578) topographic features up to 4 km 17

18 Ariel, R = 579 km 18

19 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

20 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

21 Miranda, R = 236 km best resolution ~300 m triaxial shape consistent with hydrostatic equilibrium (240x234x233) topographic features up to km 21

22 Miranda, R = 236 km 22

23 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

24 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

25 Uranian Seasons 1902 = N Winter 1923 = Equinox 1944 = N Summer 1965 = Equinox 1986 = N Winter 2007 = Equinox 2028 = N Summer 2049 = Equinox 25

26 26

27 Uranus System: 27 Satellites, Rings 27