Class Note for ASTR 206 at UA
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Date Created: 02/06/15
PYTSIASTR 206 Moons of Uranus and Neptune oAnnouncements I HW5 due now I 50 credit if submitted next Tuesday Moons o Uranus and Neptune 39 1 PTYSIASTR 206 The Golden Age of Planetary Exploration Shane Byrne shanelplarizonaedu g PYTSIASTR 206 Moons of Uranus and Neptune 3 In this lecturer o Voyager encounters 0 Rocky again I Where s the oxygen 0 Moons of Uranus I Geologic activity on some I Curious Miranda o Moons or lack of around Neptune I Triton I Capture of Triton and its effects 55 PYTSIASTR 206 Moons of Uranus and Neptune 4 Launched 1977 Currently at 108 and 88 AU Speed 16 km s391 Most instruments now switched off I but there s still one thing left to do r I 39 Pioneer 10 Pioneer 11 u39omgmi 1 3 PYTSIASTR 206 Moons of Uranus and Neptune Voyager l amp II are about to become the first interstellar spacecraft The stream of particles coming from the sun stalls at the Heliopause Voyager l is starting to feel this voyager II will follow soon Missions will probably end in the 2020s 4 Bow Shock I Heliosheath f Voyager 1 4 Termination Shock quot Voyager 2 Heliosphere Heliopatise A PYTSIASTR 206 Moons of Uranus and Neptune 6 o Voyager ll flyby very different in each case r Uranus Voyager passed through the equatorial plane D Got a good look at only one Moon i Neptune Voyager passed along the equatorial plane Belinda V O Rosallnd Epsilon Ring PUCk A Neptune 1989 Bianca pole Equator Desdemona x x Cressida 39 Juliet Uranus 1986 Ag PYTSIASTR 206 Moons of Uranus and Neptune 7 6 6 EARTH 352090 o Uranian Moons small I 13 inner moons among the ngs JOVIAN SATELLITES 73 89 0 7 e V 33 jgfqgfg ffff I 5 mIdSIzed satellltes O O 0 39 39 39 I 10irregulardistant 0mm were 39 m satellites SATURNWSATELWES a 95 3 we 3 I Named after characters 4 9e 55 5 f ng fg gaffge 54 from works of Pope amp OOo aagsoooerrfee Shakespeare TITAN MBA URANIAN SATELUTES f clt s Y9v ltr 3quot g as gs ear s g g offquot 0 Neptune has very few 0 O O O O o o o o o o o a o neerummsngenuras or I Triton is pretty large e es gyl ifg g g O O I and the reason why other 0 o e To CWquot moons are scarce PYTSIASTR 206 Moons of Uranus and Neptune 0 Solar system formation r A disk dominated by hydrogen and helium m Warmer closer to the center D Inner planets iron rich and rocky D Outer planets get bulked up with water ice Protoplanetary disks Wbble Space Telescope quotFrost line Hydrogenhelium quot ACCreting rocky Accreting rockice planetesimals planetcsimals I Transition in the asteroid belt PYTSIASTR 206 Moons of Uranus and Neptune o Jupiter forms like a mini solar system 1quot Rocky bodies close in 39 Icy bodies further out o 59 3530 Europa 94 3020 prot Jupiter Ganymede 15 1940 protosun Callisto 264 1850 callisto ZSGanymede 39 39 7 Jupiter 15 arcseconds 12 the angular diameter of the full Moon as seen from Earth Figure 131 Universe Eighth Edition to 2008 W H Freeman and Company PYTSIASTR 206 Moons of Uranus and Neptune Janus Epimelheus CJ JSIIII Saturn Orbit Inserhon Encke Cass 1 OMS Division Ring Plane Crossmg Pan 0 I 39 C ring 1 B W tutel edge Atlas A ring Mimas Enceladus Rhea f 6 ring Titan F ring Hyperion Prometheus lapetus Pandora 0 T39mquot Phoebe 196 km Mimas 1170 kg m3 Enceladus 250 km 1600 kg m3 Tethys 530 km 970 kg m3 Dione 560 km 1480 kg m3 Rhea 764 km 1230 kg m3 Iapetus 720 km 1034 kg m3 10 PYTSIASTR 206 Moons of Uranus and Neptune 11 Inner solar system 9 All Rock Jupiter s Moons 9 Rock and Ice Saturn s Moons 9 Mostly ice UranusNeptune s Moons 9 Silicate High pressure mantle ices iron core Ganymede apetus Titania Jupiter Saturn Uranus PYTSIASTR 206 Moons of Uranus and Neptune 12 All Rock Rock and Ice Inner solar system Jupiter s Moons Saturn s Moons Mostly ice 999 UranusNeptune s Moons Silicate High pressure mantle ices iron core Ganymede apetus Titania Jupiter Saturn Uranus PYTSIASTR 206 Moons of Uranus and Neptune 13 Uranus satellites have more rocky stuff not less I How did that happen I Miranda is an exception Titania 2 Ivijiefl Oberon Um39biri39el Diameter 1580km 1158km 1525km 1170km Density 1700 kg m3 1700 kg m3 1600 kg m3 1400 kg m3 MIRANDA UMBRIEL TiTANlA OBERON g PYTSIASTR 206 Moons of Uranus and Neptune 14 o What happens to oxygen I In the inner solar system it makes rocks Si 04 Decreasing I At JupiterSaturn it makes more water ice H2 0 Temperature I At UranusNeptune it makes carbon monoxide C O CO Freezes only at 68K Carbon monoxide ice on Pluto and comets etc Ag PYTSIASTR 206 Moons of Uranus and Neptune o The result is that satellites of Uranus and Neptune are I Small I Have a higher proportion of rocky material than at Saturn I Satellites of Uranus are 5065 rock GANYMEDE iii iiuerandoceann 0 We don t know if they re differentiated Rocky mantle up mum 0 Not too dissimilar from Ganymede amp Callisto quot quot quot39 7 I Except they re small 39 I Probably no iron core Icy crust Ocean Mixed icerock interior o The same happens for various other elements Ul ainusf39 i l 0 Less Important than Oxygen CH4 CO ligj H20 co NH3 N2 iii PYTSIASTR 206 Moons of Uranus and Neptune 16 Moons of Uranus Hubble detects two large outer rings Uranus has 13 Inner moons two new moons orbiting Uranus I Very dark objects albedo lt 10 like quot m 39 R the rings themselves tho newT quoty ou er rm I Waterice coated with organic 739 compounds I Cordelia and Ophelia shepherd the a ring I Mab is a source of Uranus39s outermost p ring I Rings probably generated by moon moon collisions Orbit Puck 160km across E39s PYTSIASTR 206 Moons f Uranus and Neptune There are five much larger regular satellites I Encounter geometry means that only one satellite was well imaged I The southpolar region of each Moon was seen 3M0r 5mm Emmiqu v D UMBRIEL TlTANlA 470km 11001200 km 15001600 km Good pictures Not so good pictures from Voyager from Voyager PYTSIASTR 206 Moons of Uranus and Neptune 1s Oberon and Titania 1500km across Oberon I Poor imaging I Large craters visible Bright ejecta V Dark floor deposits Titania I Fault bounded canyons I Massive extension Shrinking surface layer Expanding core I Faults crosscut impact craters I Fewer large crater than Oberon Similar in size to Rhea at Saturn I but much more activity here I Higher silicate levels provide more heat PYTSIASTR 206 Moons of Uranus and Neptune 19 Umbriel and Ariel 1100km across Umbriel I Craters are the only landform I No endogenic geology visible I Volatiles concentrated in polar regions Ariel I Extensive network of fault bounded canyons I Canyon floors resurfaced by viscous flows Upbowing crosssections with central sinuous troughs I Mix of surface ages implies longlived activity I Tidal heating in the past A PYTSIASTR 206 Moons of Uranus and Neptune 20 0 Density not size determines amount of activity I Higher density caused by having more rock I More rock means more heat from radioactive elements 0 Past tidal heating also a possibility Titania Ariel Oberon Umbriel Diameter 1580km 1158km 1525km 1170km Density 1700 kg m3 1700 kg m3 1600 kg m3 1400 kg m3 Albedo 03 04 02 02 g PYTSIASTR 206 Moons of Uranus and Neptune 21 o Miranda 472km across r Discovered by Kuiper 1948 39 Old cratered plains uniform r Coronae l Tectonic disruption of surface l In lling with very viscous magmas PYTSIASTR 206 Moons of Uranus and Neptune 22 0 Small size makes activity hard to explain l Low density means little rock i and little radiogenic heat u Energy must have been tidal u Resonance with Umbriel might also explain Miranda s 4 orbital quot inclination 0 System may have slipped out of a I M resonance that Europa and lo have lg today i Pulled the plug on Miranda s geologic activity PYTSIASTR 206 Moons of Uranus and Neptune 23 Moons of Neptune SYMNF WS radius 0 Small inner satellites o Proteus L Largest is Proteus 400km in Roche mm diameter p Roche limit V 2 I I D p Thalassa esta Naiad vi Other inner satellites herd ring particles Ag PYTSIASTR 206 Moons of Uranus and Neptune o Neptune s moons are most famous for not being there I Outside 5 Neptune radii there are only two moons Triton and Nereid I Why so few moons It s all Triton s fault 9 0 EARTH 230 JOVIAN SATELLITES 7 7 4 539 if 401339 k s t x O O O O gg y eq f 95 O o o o o a n n a 5mm cmsvo 390 EUROPA SATURNIAN SATELLITES 9 3 f 4quot so 3 URANIAN SATELUTES 0 F 29 x a39 6quot w T QVS 390 39 5 0 4 5 0 lt7 lt5quot a s s s qwy f 0000009001 NEPTUNIAN SATELUTES 39a or ae x gff S QQ 0 O O O G a a n o c 0 sum Ag PYTSIASTR 206 Moons of Uranus and Neptune 25 Triton Moon 10 Europa Ganymede Callisto Titan Triton Parent planet Earth Jupiter Jupiter Jupiter Jupiter Saturn Neptune Diameter km 3476 3642 3130 5268 4806 5150 2706 i39111s1ltg 735 X 1013 893 X 1031 480 X 1013 148 X 1011 108 X 1031 134 X 1011 215 X 1011 Average density kgm1 3340 3530 2970 1940 1850 1880 2050 Substantial atmosphere No No N0 N0 No Yes No Europa Ganymede JPLNASA R In U X G That s a bit unfair Triton has a thin nitrogen atmosphere A PYTSIASTR 206 Moons of Uranus and Neptune 26 o Perfectly circular orbit 1433 RN I No current tidal heating I Retrograde orbit I Density 2050 kg m3 o Spiraling inward I Will reach the Roche limit in 36 billion years ICE l SHELL possible ocean 0 Structure probably close to Ganymede I Complete differentiation I Ice l shell thickening downwards I Ice llllll shell thickening upwards I Sandwiched ocean expected Ag PYTSIASTR 206 Moons of Uranus and Neptune 0 Triton has a thin nitrogen atmosphere I Pressure is 19 microbars I 150000th of Earth s pressure 0 High reflectivity 85 I Very cold surface 3839 K I Nitrogen freezes into ice in the winter polar regions I Sublimates back into a gas in the summer polar region I Very similar to CO2 on Mars 0 lt0 30 0 SubSolar Latitude 30 JAVA AVAVAJ VW 1000 1500 Date AD 2000 2500 27 g PYTSIASTR 206 Moons of Uranus and Neptune 28 I 0 N2 ice quickly anneals into a transparent layer b quot J I Seasonal frost gt transparent slab C Incident solar radiation absorbed beneath the ice I Subsurface sublimation 39 I Nitrogen gas escapes in jets 8km high m D Implies a 230 m s1 flow r I Similar to CO2 jets on Mars 39 39 a wind direction PWSIASTR 206 Moons of Uranus and Neptne 4 90 Cantaloupe terrain I Close packed elliptical features I Regularly spaced I Nonoverlapping 1 Rising blobs of low density ice I Diapirs Rough ll Smooth L Prediapir Stratigraphy 0 50 km PA lt PB lt Po llllll PYTSIASTR 206 Moons of Uranus and Neptune 0 Where did Triton come from I Very different than other satellites of Uranus and Neptune I Similarities to Pluto and Kuiper Belt I Retrograde orbit points to it being a captured object o Gravitational capture needs some dissipate energy 0 Did Triton I Hit another moon of Neptune I Hit another Kuiper Belt Object that happened to be passing by I Come in as a binary system and have its twin escape Pluto and Charon Binary Kuiper Belt Objects 31 11 PVTSIASTRQQB of Uranus and Neptune 3 2 1 0 0 Triton captured into large and highly eccentric orbit a I Tidal forces reduce the orbital eccentricity 26 r o Tides are still shrinking Tritons orbit 39 P I It will pass Neptune s Roche limit in about 36 3394 billion years I which means the end of Triton o 166Lw 66m 3960L 400 500 139 I106 years 0 Triton was severely heated by tides I Melting generates liquid layer I Runaway heating D Whole body perhaps molten D Lots of cryovolcanism I Complete differentiation easy I Greenhouse atmosphere D Surface temps 100200K 353 PYTSIASTR 206 Moons of Uranus and Neptune 33 o What about the rest of Neptune s system I The other moons did not escape unscathed from Triton s capture I Interactions with the massive Triton flung them into disordered crossing orbits I Many moonmoon collisions probably resulted in a ring system I Many more moons were probably thrown into Neptune URANIAN SATELUTESI ifquot 39 a 3 Y 9 r 439 K 9 w J H e 52 v atquot 6 3 a s 3 a f retreat ffdiff O o O O 0 0 0 o o I I c n NEPTUMAN SATELUTES Es PYTSIASTR 206 Moons of Uranus and Neptune 34 Capture of Triton I Removes all moons more that 5 Neptune radii from the planet I Only Nereid 340km survived this Ended up in a very far flung orbit Inclined by 28 Very eccentric War 5mm Smulzlot MO g PYTSIASTR 206 Moons of Uranus and Neptune In this lecture o Voyager s 30 year mission 0 Nearing the edge of the solar system 0 Satellites of Uranus and Neptune are denser than you d expect 0 Oxygen gets tied up as the gas carbon monoxide 0 Less water ice so the rock percentage is higher 0 Satellites Of Uranus 0 Inner satellites are dark like the rings they produce 0 Regular satellites show past geologic activity 0 Miranda had extreme activity that was abruptly terminated o Neptune lacks a well developed satellite system 0 Triton is likely a captured half of a binary Kuiper Belt Object 0 Capture melts Triton and destroys a lot of other moons Next Pluto and the rest of the Kuiper belt 0 Reading 0 Chapter 14 to revise this lecture 0 Chapter 14 for next lecture 35
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