gas giants. Mostly hydrogen and helium, atms ~1000km thick, liquid h interiors (high pressures, liquid metal at v high pressures), rocky cores (rock, ice, metal, etc w temps of > 20k C). Uranus/Neptune: Ice giants. Atms: H, He, methane (absorbs red light giving planets blue color). Mantle: water, ammonia, methane ices (superheated 2,500-5k C and high pressure), core: rocks and ices. Weather: clouds divided into bands, lightly-colored zones and relatively dark belts. Runs east-west, parallel to the equator. Bounded by wind flows called jets ( due to planet’s rapid rotational speeds). Jovian spots are storms called ovals (high pressure anti cyclone systems, can’t move north-south. Lifetime from several days to centuries (depending on size, 1-6k km dia storms: 1-3 years. Jupiter’s great red spot: 25k across, first observed over 340 years ago. Saturn’s layers are the same as Jupiter’s, but deeper in- more subdued. Serpent Storm on Saturn. Uranus: nearly featureless disk. 84 year orbit. Spin axis tilt (98 deg) forces seasons. Seasonal changes on Uranus: as uranus’ seasons have progressed from (southern) summer to fall, weather activity has increased. Neptune: more earth-like tilt of 30 deg. Cloud bands, large storms ( great dark spot, 2,400 kph winds), white high- altitude clouds (frozen methane). Jovian planet moons: large moons (> 1500 km, many have ongoing geological activity). Medium-sized moons (300-1,500km, most had geological activity in past), small moons (<300 km, no geological activity). Jupiter’s Galilean Moons: Io, Europa, Ganymede, Callisto. Io is the most volcanically active body in the SS. Jupiter’s gravity deforms Io: creates tidal bulges on its near and far sides; bulges are largest when Io is nearest Jupiter in its elliptical orbit. Changing bulges flexes Io: heats Io’s interior. Europa’s ice surface is criss-crossed with ridges. May house a deep liquid water ocean. Ganymede: largest moon in SS, bigger than mercury. Composition: 50/50 rock/ice. Two terrain surface: dark, heavily cratered regions (30%), lighter grooved terrain, richer in water ice (70%). Callisto: heavily cratered ice ball, furthest of the Galilean moons from Jupiter (little tidal heating from Jupiter). Ancient surface, no recent geological activity. Titan: Saturn’s largest moon; 2 nd largest in SS; has an atms. Thick hazy atms mostly of N2 but also argon, methane, ethane. 60% greater pressure at surface than Earth’s. Cold! -180C at surface. Surface: rocks made of ices, erosion by liquid methane and ethane. Titan’s “great ethane lake”. Plumes of icy material extend above the southern polar region of Saturn’s moon Enceladus . Neptune’s Moon Triton: Impact craters filled by lava, like the moon’s maria, but lava was “molten ice.” Triton orbits Neptune backwards (suggests Neptune captured it). Triton was probably part of a two-body object similar to the Pluto-Charon system (pair strayed too close to Neptune, companion escaped but left Triton behind). Saturn possesses the most extensive planetary ring system of any planet in our SS. Rings are made of billions of ice particles . (99.9% pure water ice). Primarily made of particles from 1cm to 10m across. Ring particles clump together.
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