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Chapter 8 Jovian Systems What are jovian made of? Density Differences

2 1.5 • and 1 are denser than 0.5 because they have less H/He, proportionately. Density (g/cc) 0

JupiterSaturnUranus Neptune

What are jovian planets like on the inside? Inside

• High pressure inside of Jupiter causes the phase of to change with depth.

• Hydrogen acts like a metal at great depths because its move freely. Jupiter’s

Aurora on Jupiter

• Jupiter’s strong gives it an enormous magnetosphere. • Gases escaping feed the donut-shaped Io torus. What is the structure of Jupiter like?

1. Rocky core, thin atmosphere 2. Rocky core, thick atmosphere 3. Gaseous on the outside, then liquid hydrogen, more dense metallic hydrogen, rocky core 4. Gaseous on the outside, then liquid hydrogen, then , then the other elements Jupiter does not have a large metal core like the . How can it have a magnetic field? 1. The magnetic field is left over from when Jupiter accreted. 2. Its magnetic field comes from the . 3. It has metallic hydrogen inside, which circulates and makes a magnetic field. 4. That’s why its magnetic field is weak. What are Saturn’s rings like? Earth-Based View Spacecraft View of Ring Gaps Artist’s Conception of Close-Up Gap

• Some small moons create gaps within rings. Jovian Ring Systems

• All four jovian planets have ring systems. • Others have smaller, darker ring particles than does Saturn. Why do the jovian planets have rings? • They formed from dust created in impacts on moons orbiting those planets.

How do we know this? How do we know?

• Rings aren’t leftover from planet formation because the particles are too small to have survived this long. • There must be a continuous replacement of tiny particles. • The most likely source is impacts with the jovian moons. Ring Formation

• Jovian planets all have rings because they possess many small moons close-in. • Impacts on these moons are random. • Saturn’s incredible rings may be an “accident” of our time.