Uranus Tilt Q. 45: Uranus’s Giant Impact Caused by giant impact? Unusual seasons Q. 45: Uranus’s Giant Impact

Uranus and Neptune – Colors and Bands Clouds form deep Difficult to see Methane absorbs red light Methane scatters blue light Makes them blue

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

Uranus and Neptune – Storms Like Jupiter and Saturn, Uranus and Neptune have big storms Neptune Uranus

Neptune’s Great Dark Spot Neptune’s super storm Smaller than Red spot It has subsequently disappeared New spot appeared in northern hemisphere

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: 400-2000 km Small: < 400 km Jupiter Io Europa Ganymede Callisto Saturn Enceladus Titan Iapetus Neptune Triton Uranus Miranda Mars Phobos Deimos Pluto Charon Earth Moon

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

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

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

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

Io A little bigger than our moon Colorful mottled appearance No craters Volcanoes!

Io - Composition Rocky Mantle Metal Core No ice/water

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

Volcanoes on the Surface

Volcanoes on the Surface

Active Volcanoes Q. 47: Io and Craters

Resurfacing at Work

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

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

Europa A little smaller than our moon Thin ice layer Cracked icy appearance Less tidal heating Very few craters

Europa – Cracks and Surface Covered in ice, mostly water ice Heating causes stresses that cause cracks Few craters  resurfacing (melting)

Europa’s Cracked Surface

Europa’s Cracked Surface

Europa’s Cracked Surface

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

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

Ganymede – Dark and Light regions Ice broke apart Water welled up and froze

Ganymede – Pressure Ridges Expanding ice Ice deforms

Ganymede – Craters Many craters But not like the Moon

Ganymede – Craters Over time, ice can flow, slowly Plastic deforma-tion Craters get flattened over time

Callisto Same size as Mercury Composition: some rock, mostly water ice Heavily cratered

Craters on Callisto Crater chains

Craters on Callisto Valhalla Crater

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