Lecture 8: Jovian (Giant) Planets SCI238 W08 Lecture 8: Jovian (Giant) Planets Neptune and Triton image from Voyager 2 spacecraft (1989) L8 – Jan 31/08 Jovian Planets

This week’s events: the Moon: New Moon Feb 7 Venus: visible low in east before sunrise; brightest “morning” star Mars: is visible all night, rises at sunset Jupiter: passing Venus. take a look at 6am 1 -3 Feb! Saturn: rises at 8pm L8 – Jan 31/08 Jovian Planets

Today’s Lecture announcements etc… Moon terrestrial planets compared assignment 2, also posted on course webpage Moon terrestrial planets compared overview of the Giant Planets interiors “surface” features atmospheres magnetic structures moons rings L8 – Jan 31/08 Jovian Planets

Moon’s interior differentiated, but not as “extreme” differences as Earth L8 – Jan 31/08 Jovian Planets

Craters on the Moon are due to impact events Impact craters found throughout SS L8 – Jan 31/08 Jovian Planets

Impact process forms characteristic shape... ejecta circular, rimmed, low floor L8 – Jan 31/08 Jovian Planets

Maria and Highlands are different in age How do we know? L8 – Jan 31/08 Jovian Planets

Apollo astronauts returned samples from many locations L8 – Jan 31/08 Jovian Planets

Lunar samples: radioactive dating => relation between surface density of craters and age 40,000 60,000 # Craters (>1km) 4 2 Age of Surface Deposit (Gyr) age of oldest samples: ~4.4x109 yr (highlands) maria samples: ~3x109yr youngest lunar surface samples ~109yr L8 – Jan 31/08 Jovian Planets

What is the pattern (correlation) here? Terrestrial surfaces have different “ages” What is the pattern (correlation) here? Crustal rock solidified globally first on Moon, last on Earth L8 – Jan 31/08 Jovian Planets

Comparative Planetology… interiors – role of mass atmospheres – role of mass, distance from sun surfaces – liquid water, lava, tectonics, impacts, surface age L8 – Jan 31/08 Jovian Planets

All terrestrial bodies are differentiated => All had hot (and fluid) interiors at some time L8 – Jan 31/08 Jovian Planets

Larger terrestrial planets: cooled more slowly more and longer lasting tectonic activity easier to retain atmosphere L8 – Jan 31/08 Jovian Planets

For planets closer to the sun: higher T harder to retain liquid water, atmospheres L8 – Jan 31/08 Jovian Planets

higher rotation => more “weather” L8 – Jan 31/08 Jovian Planets

fewer impact craters on massive planets: cooled more slowly atmospheres shield only against small impactors L8 – Jan 31/08 Jovian Planets

Giant Planets size interiors atmospheres, rapid rotation, circulation magnetic fields satellites rings L8 – Jan 31/08 Jovian Planets

Physical Properties of the Jovian Planets (mostly Earth units) radius mass Density (kg/m3) Prot (d) axis tilt Mag. field? gsurf Earth 6,378km 5.97×1024 kg 5,520 0.9973 23.45 Y 9.8m/s2 Jupiter 11.2 317.9 0.24 0.41 3.08 2.36 Saturn 9.5 95.2 0.12 0.44 26.73 0.92 Uranus 4.0 14.5 0.23 -0.72 97.92 0.91 Neptune 3.8 17.1 0.30 0.67 29.6 y 1.14

Jovian planets: size comparison Jupiter by far the largest all >> Earth Uranus, Neptune similar L8 – Jan 31/08 Jovian Planets

the giant planets are rapidly rotating, large “gravitationally bound” balls of fluid. although gravity tends to pull fluid together into a sphere, rotation flattens this into an “ellipsoid”. L8 – Jan 31/08 Jovian Planets

Saturn is the most oblate giant planet Rpolar = 0.9 Requatorial L8 – Jan 31/08 Jovian Planets

Jupiter’s interior is differentiated mostly metallic H! core: rocky+metallic +H compounds L8 – Jan 31/08 Jovian Planets

Jovian planets: all have differentiated interiors Cores all ~10-15MEarth J,S: higher % H, H compounds U,N: higher % rocky, H mostly in methane, ammonia L8 – Jan 31/08 Jovian Planets

The Structure of Jupiter’s Atmosphere as with terrestrial atmospheres: clouds, T, altitude L8 – Jan 31/08 Jovian Planets

atmospheres ~same structure… differences: Tmax, pressure, some composition L8 – Jan 31/08 Jovian Planets

Bands in Jupiter’s atmosphere: result of heat, convection, rotation (Coriolis) visible light image IR image L8 – Jan 31/08 Jovian Planets

the colour differences between various components of Jupiter’s atmosphere combined with the circulation pattern produce distinctive banding structure. L8 – Jan 31/08 Jovian Planets

Jupiter’s Great Red Spot is a high pressure storm region L8 – Jan 31/08 Jovian Planets

…and the white spot is a low pressure storm region L8 – Jan 31/08 Jovian Planets

…and now Jupiter has a second large red storm L8 – Jan 31/08 Jovian Planets

Saturn too has bands and storms, but less prominent L8 – Jan 31/08 Jovian Planets

Neptune and Uranus’ blue colour: methane absorbs red λ and reflects blue L8 – Jan 31/08 Jovian Planets

all 4 jovian planets have strong magnetic fields and huge magnetospheres Uranus’ and Neptune’s magnetic fields strongly tilted re rotation axis L8 – Jan 31/08 Jovian Planets

we also see auroral zones near the magnetic poles L8 – Jan 31/08 Jovian Planets

3/4 Jovian planets have internal heat sources TBB(obs) “total” Power Internal Power Jupiter 127K 2x input 4x1017 W Saturn 97 2.8x 2x1017 Uranus 58 ~1x 1015 Neptune 56 2.5x 3x1015 Primordial heat? Helium rain? Other? L8 – Jan 31/08 Jovian Planets

Jupiter: strongest, most colourful bands, storms… L8 – Jan 31/08 Jovian Planets

Jupiter very layered atmosphere strong magnetic field no true surface hydrogen/helium, methane, ammonia, water strong “banding” – seeing different cloud layers white at depth “0 km” is ammonia red at depth 25 km is ammonia hydrosulphide blue at depth 100 km is water ice Giant Red Spot – a giant storm seen since first telescope viewed Jupiter, fading a bit perhaps, but still 40,000 km wide; and now another! strong magnetic field no true surface very oblate planet (fast rotation) hotter than expected – but not Greenhouse effect planet is contracting! mostly H/He interior with metallic H and rocky core L8 – Jan 31/08 Jovian Planets

Saturn: prominent ring system, more subtle bands L8 – Jan 31/08 Jovian Planets

Saturn similar to Jupiter but smaller layered banded atmosphere hydrogen/helium, methane, ammonia strong magnetic field metallic hydrogen and rocky core rings are most massive and prominent of all L8 – Jan 31/08 Jovian Planets

Cassini-Huygens mission to Saturn a joint NASA-ESA mission to explore Saturn and its moons web site at saturn.jpl.nasa.gov reached Saturn 30 June, 2004 (after seven year flight) now in 4 year mission, orbiting through the Saturn system recent results: in the midst of series of flybys of Titan (last on 15 Jan. 2006) Huygens probe toTitan Jan 24/2005 landed in mud has found water ice, methane springs, rivers with islands Epimetheus (30 Mar. 2005) L8 – Jan 31/08 Jovian Planets

Uranus: almost completely featureless in visible light but shows more detail in IR L8 – Jan 31/08 Jovian Planets

Uranus accidentally discovered telescopically in 1781 faint features, blue atmosphere hydrogen, helium, methane, BUT NO AMMONIA strong magnetic field hydrogen NOT metallic, rocky core rotation axis tilted 98o → very strong seasonal effect L8 – Jan 31/08 Jovian Planets

Neptune shows large storm features, like Jupiter the storms change over timescales of years or less L8 – Jan 31/08 Jovian Planets

Neptune position predicted from observations of Uranus discovered in 1846 very similar to Uranus, but more methane more cloud features warmer(!) than Uranus L8 – Jan 31/08 Jovian Planets

Jovian satellites: some large, many small some have been geologically active: now or in the past some formed with planet, some captured L8 – Jan 31/08 Jovian Planets

Jupiter’s Large Satellites Io geologically active (with active volcanoes!) covered in orange sulphur compounds strongly tied to Jupiter’s magnetic field Europa smooth surface with few craters water ice, possibly over liquid water Ganymede largest moon in the Solar System water ice over much of surface Callisto heavily cratered concentric circular ridges are signs of a large impact L8 – Jan 31/08 Jovian Planets

the four “Galilean” satellites of Jupiter Io Europa Ganymede Callisto surface “age” ↑ and mean density ↓ with distance from Jupiter L8 – Jan 31/08 Jovian Planets

Io: most volcanically active body in SS L8 – Jan 31/08 Jovian Planets

Io: volcanoes are frequent …constantly changing surface appearance L8 – Jan 31/08 Jovian Planets

Io: tidal interaction and eccentric orbit heat its interior L8 – Jan 31/08 Jovian Planets

Io, Europa, Ganymede: and orbital resonance L8 – Jan 31/08 Jovian Planets

Charged particles escaping Io interact with Jupiter’s magnetosphere => Io torus Periodic variability in radio emission from torus first observed in 1960s L8 – Jan 31/08 Jovian Planets

Europa’s smooth surface and cracked terrain the result of tidal heating and icy composition L8 – Jan 31/08 Jovian Planets

just below Europa’s surface: liquid water or warm convecting ice? L8 – Jan 31/08 Jovian Planets

Ganymede’s surface shows both old and young regions L8 – Jan 31/08 Jovian Planets

Callisto’s surface is the “oldest” of the four Galilean satellites L8 – Jan 31/08 Jovian Planets

L8 – Jan 31/08 Jovian Planets

Saturn’s Moons many moons, but probably a large number still to be discovered Titan: largest of Saturn’s moon’s – has a thick atmosphere, extending far out into space, probably has frozen water (ice) innermost moons tidally locked to planet moons interact with rings L8 – Jan 31/08 Jovian Planets

Titan: Saturn’s largest moon; has a thick atmosphere methane, nitrogen… smoggy L8 – Jan 31/08 Jovian Planets

Huygens probe shows some surface features on Titan Titan: icy “rocks”, “river” valleys… L8 – Jan 31/08 Jovian Planets

Saturn’s Moons are varied, enigmatic deathstar Mimas icy Enceladus cratered Tethys old Dione streaky Rhea two-faced Iapetus L8 – Jan 31/08 Jovian Planets

Uranus’ moons more than 20 small ones, some irregular in shape, some retrograde five midsized: Miranda, Ariel, Umbriel, Titania, Oberon All icy, varied geological history Miranda is strange – very fractured surface, some cataclysmic event? L8 – Jan 31/08 Jovian Planets

near IR image shows Neptune’s rings and seven of its moons L8 – Jan 31/08 Jovian Planets

Urabus’ Miranda shows a fractured surface, obvious violence, but from what? messed-up Miranda L8 – Jan 31/08 Jovian Planets

Neptune’s moons five small inner moons near ring system two larger, icy… five small outer, retrograde Triton very much larger than any other Neptune moon has thin nitrogen atmosphere surface has nitrogen geysers retrograde (backwards) orbit spiraling in towards Neptune L8 – Jan 31/08 Jovian Planets

Triton: moon of Neptune Nitrogen atmosphere surface has been reshaped by geological activity L8 – Jan 31/08 Jovian Planets

Saturn’s Rings: the brightest, best known within “Roche Limit” of Saturn where any large rocks (moons) break up due to tidal effects major rings (“A”, “B”, and “C”) with gaps between them “Cassini’s Division” composed of icy particles with sizes between 1 micron and 10 meters Voyager discoveries: several other rings fine rings within each ring, like record grooves: “spiral density waves” short-lived spokes braided rings “shepherd” satellites rings are very thin – at most a few tens of meters L8 – Jan 31/08 Jovian Planets

Saturn’s rings are wide, thin, and complex Radio image colours -> particle size purple: mainly >5cm green: mainly <1cm white: particle density too high L8 – Jan 31/08 Jovian Planets

Shepherd moons control the width of rings… L8 – Jan 31/08 Jovian Planets

…and also make gaps L8 – Jan 31/08 Jovian Planets

“spokes” in Saturn’s rings: charged particles briefly suspended above the plane? L8 – Jan 31/08 Jovian Planets

Galileo spacecraft shows rings around Jupiter ring particles are small and dark: debris from Metis.. L8 – Jan 31/08 Jovian Planets

Near IR image shows rings around Uranus and some of its moons L8 – Jan 31/08 Jovian Planets

Neptune’s rings are narrow and bright with dusty regions L8 – Jan 31/08 Jovian Planets