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Uranus Tilt Q. 45: Uranus’s Giant Impact Caused by giant impact?
Unusual seasons Q. 45: Uranus’s Giant Impact
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Uranus and Neptune – Colors and Bands
Clouds form deep Difficult to see Methane absorbs red light Methane scatters blue light Makes them blue
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Uranus and Neptune – Bands and Clouds
False color Like Jupiter and Saturn, Uranus and Neptune have bands Near surface, these planets can have methane ice clouds
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Uranus and Neptune – Storms
Like Jupiter and Saturn, Uranus and Neptune have big storms Neptune Uranus
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Neptune’s Great Dark Spot
Neptune’s super storm Smaller than Red spot It has subsequently disappeared New spot appeared in northern hemisphere
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Moons of the Jovian Planets
Moon Size Moons orbit planets or other objects We will categorize them by: Size Origin Size categories, by diameter: Large: >2000 km Medium: km Small: < 400 km Jupiter Io Europa Ganymede Callisto Saturn Enceladus Titan Iapetus Neptune Triton Uranus Miranda Mars Phobos Deimos Pluto Charon Earth Moon
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Moon Shape and Composition
Large are round and differentiated Rock and metal inside Ices (mostly water) outside* No atmosphere** Medium are round, not differentiated Rock, metal, ices no atmosphere, mixed Small are any shape, not differentiated Rock, metal, ices* no atmosphere, mixed *Terrestrial moons and Io have no ices **Titan and Triton have atmosphere
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Moon Origins Moon Rotation
When large planets formed, they sometimes had their own disks Like mini solar systems These coalesced into moons These moons go around the same way the planets rotate Sometimes, moons are captured by planets much later These moons usually go around backwards Moon Rotation Moons are gravitationally dominated by their planets Usually tidally locked to the planet Like our moon
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Moons of Jupiter Q. 46: Shape of Io Amalthea Thebe Adrastea Metis
4 large moons Io Europa Ganymede Callisto 75 known small moons Q. 46: Shape of Io Amalthea Thebe Adrastea Metis
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Galilean Moons of Jupiter - Size
Io Ganymede Callisto Europa Moon Inner two comparable to Moon Outer two comparable to Mercury All have virtually no atmosphere All are tidally locked to Jupiter Mercury
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Io A little bigger than our moon Colorful mottled appearance
No craters Volcanoes!
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Io - Composition Rocky Mantle Metal Core No ice/water
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Io’s Color and Volcanoes
Io covered with active volcanoes Volcanoes spew out sulfur Variety of sulfur compounds have different colors Sulfur responsible for Io’s colors
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Volcanoes on the Surface
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Volcanoes on the Surface
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Active Volcanoes Q. 47: Io and Craters
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Resurfacing at Work
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Where Does the Heat Come From?
Io too small for radioactivity to keep warm Tidal heating keeps it hot Changing shape as distance changes Flexing generates heat Jupiter Io Q. 48: Relative Tidal Heating of Moons
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Jovian Moons and Tidal Heating
Tidal effects get smaller with distance (Io is closest) Gravity has biggest effect on large moons All Galilean moons are about the same size Io a tad larger
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Europa A little smaller than our moon Thin ice layer
Cracked icy appearance Less tidal heating Very few craters
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Europa – Cracks and Surface
Covered in ice, mostly water ice Heating causes stresses that cause cracks Few craters resurfacing (melting)
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Europa’s Cracked Surface
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Europa’s Cracked Surface
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Europa’s Cracked Surface
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Europa’s Composition Metal core Rocky Mantle “Thin” layer of water
Prospects for life? Lots of water No sunlight Many terrestrial forms of life survive on thermal vents
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Ganymede Largest moon in solar system Larger than Mercury!
Dark regions separted by lighter ice Composition: half rock, half water ice Many craters Little tidal heating
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Ganymede – Dark and Light regions
Ice broke apart Water welled up and froze
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Ganymede – Pressure Ridges
Expanding ice Ice deforms
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Ganymede – Craters Many craters But not like the Moon
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Ganymede – Craters Over time, ice can flow, slowly
Plastic deforma-tion Craters get flattened over time
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Callisto Same size as Mercury Composition: some rock, mostly water ice
Heavily cratered
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Craters on Callisto Crater chains
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Craters on Callisto Valhalla Crater
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Patterns in Jupiter’s Moons
Europa thin ice Callisto mostly ice Io no ice Ganymede half ice Moons have more ice the farther they are from Jupiter Why? Early Jupiter was extremely hot Sometimes called a “failed star” Heated neighborhood very hot Water evaporated from inner moons Q. 49: Ice on Jupiter’s Moons
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