Jupiter

Largest and most massive planet in the solar system Contains almost ¾ of all planetary matter in the solar system. Explored in detail by several space probes: Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, Galileo Most striking features visible from Earth: Multi-colored cloud belts Visual image Infrared false- color image

Exploration of Jupiter Previous Missions Pioneer 10 & 11 Voyager 1 & 2

Latest Jupiter Mission Galileo ( )

Galileo Probe What did it tell us? What did we expect?

Jupiter’s Rotation Jupiter is the most rapidly rotating planet in the solar system Rotation period slightly less than 10 hr. Centrifugal forces stretch Jupiter into a markedly oblate shape.

Jupiter’s Atmosphere Jupiter’s liquid hydrogen ocean has no surface: Gradual transition from gaseous to liquid phases. Only very thin atmosphere above cloud layers; transition to liquid hydrogen zone ~ 1000 km below clouds.

Jupiter’s Cloud layers Haze (at the top) Ammonia Ammonium Hydrosulfide Water (lowest observed layer) What did the Probe find?

At depth of 1 bar (Earth Sea level): T = 130 K (-225 F), P=1 bar Survived to a depth of 150 km: T = 425 K (305 F), P=22 bars Hotter and denser than expected Ammonia and water layers were not detected Wind velocities much greater (435 mph) Chemically like Sun in terms of H, He, but a bit off in other elements

Jupiter’s Atmosphere Three layers of clouds: 1. Ammonia (NH 3 ) crystals 2. Ammonia hydrosulfide (NH 4 SH) 3. Water crystals Heating mostly from latent, internal heat

Observations of Jupiter from the Earth reveal clouds and atmospheric structures Belts Zones

The Cloud Belts of Jupiter Dark belts and bright zones. Zones higher and cooler than belts; high-pressure regions of rising gas.

The Cloud Belts on Jupiter Just like on Earth, high-and low-pressure zones are bounded by high-pressure winds. Jupiter’s Cloud belt structure has remained unchanged since humans began mapping them.

Clouds, clouds, clouds Rotation rate is about 10 hours Differential Rotation (different parts rotate at different rates) Produces turbulence, and storms © Calvin Hamilton

The Great Red Spot 8-year sequence of images of the Great Red Spot on Jupiter Has been visible for over 400 years Giant storm system similar to Hurricanes on Earth: Wind speeds of 430 km/h (= 270 miles/h) Changes appearance gradually over time

The Great Red Spot A storm that has been going on for nearly 400 years 2-3 x size of the Earth

The History of Jupiter Formed from cold gas in the outer solar nebula, where ices were able to condense. Rapid growth Soon able to trap gas directly through gravity Heavy materials sink to the center In the interior, hydrogen becomes metallic (very good electrical conductor) Rapid rotation → strong magnetic field Rapid rotation and large size → belt-zone cloud pattern Dust from meteorite impacts onto inner moons trapped to form ring

Jupiter’s Magnetic Field Magnetic field at least 10 times stronger than Earth’s magnetic field. Magnetosphere over 100 times larger than Earth’s magnetosphere

Aurorae on Jupiter Just like on Earth, Jupiter’s magnetosphere produces aurorae concentrated in rings around the magnetic poles. ~ 1000 times more powerful than aurorae on Earth. Particles producing the aurorae originate mostly from moon Io

Aurora requires a magnetic field What’s Jupiter’s magnetic field like? How is it produced?

Rock and Metal Liquid Metallic Hydrogen Liquid Hydrogen Molecular Hydrogen

Jupiter’s Ring System

Jupiter’s Ring Not only Saturn, but all four gas giants have rings. Jupiter’s ring: dark and reddish; only discovered by Voyager 1 spacecraft. Galileo spacecraft image of Jupiter’s ring, illuminated from behind Composed of microscopic particles of rocky material Location: Inside Roche limit, where larger bodies (moons) would be destroyed by tidal forces.

Satellites of Jupiter Currently 60+ known satellites - most Most small asteroid-like, only a few km in size 4 largest satellites are the Galilean Satellites Io, Europa, Ganymede, Callisto

The Galilean Satellites

Io - The Volcanic World

Io: Bursting Energy Most active of all Galilean moons; no impact craters visible at all. Over 100 active volcanoes! Interior is mostly rock. Activity powered by tidal interactions with Jupiter.

Surface features have changed since the Voyager spacecraft visited (1979) and the Galileo spacecraft’s observations (late 1990’s)

Continual volcanic eruptions Why?

Io has the highest density Io has the fewest craters - youngest surface Io is closest to Jupiter And on the other side are the other 3 large satellites Io is a victim of a tug of war (tidal heating) due to Jupiter and the other moons!

Jupiter’s Influence on its Moons Presence of Jupiter has at least two effects on geology of its moons: 1. Tidal effects: possible source of heat for interior of Ganymede 2. Focusing of meteoroids, exposing nearby satellites to more impacts than those further out.

Interactions with Jupiter’s Magnetosphere Io’s volcanoes blow out sulfur-rich gases → tenuous atmosphere, but gases can not be retained by Io’s gravity → gases escape from Io and form an ion torus in Jupiter’s magnetosphere. → Aurorae on Jupiter are fueled by particles from Io

Europa - The Ice World

Europa: A Hidden Ocean Close to Jupiter → should be hit by many meteoroid impacts; but few craters visible. → Active surface; impact craters rapidly erased.

The Surface of Europa Cracked surface and high albedo (reflectivity) provide further evidence for geological activity.

Ice features that are slowly changing Very few craters Lower density than Io Slightly older surface

The Interior of Europa Europa is too small to retain its internal heat → Heating mostly from tidal interaction with Jupiter. Europa has a liquid water ocean ~ 15 km below the icy surface.

Ganymede - The Largest Moon

Ganymede: A Hidden Past Largest of the 4 Galilean moons. Rocky core Ice-rich mantle Crust of ice 1/3 of surface old, dark, cratered; rest: bright, young, grooved terrain Bright terrain probably formed through flooding when surface broke

Light and Dark Terrain indicates some resurfacing

Lower Density More craters, Less resurfacing Older surface than Europa

Callisto - The Cratered Moon

Callisto: The Ancient Face Tidally locked to Jupiter, like all of Jupiter’s moons. Composition: mixture of ice and rocks Dark surface, heavily pocked with craters. No metallic core: Callisto never differentiated to form core and mantle. → No magnetic field. Layer of liquid water, ~ 10 km thick, ~ 100 km below surface, probably heated by radioactive decay.

Valhalla Impact Basin - rings extend out 1500 km

Lowest Density Most craters Very little resurfacing Oldest surface