Chapter 8Jovian Planet Systems

What are jovian planets made of?

Density Differences

0

0.5

1

1.5

2

Jupite

r

Satu

rn

Ura

nus

Nep

tune

Den

sity

(g

/cc

)

• Uranus and Neptuneare denser than Saturnbecause they have lessH/He, proportionately.

What are jovian planets like onthe inside?

Inside Jupiter• High pressure inside

of Jupiter causes thephase of hydrogento change withdepth.

• Hydrogen acts like ametal at great depthsbecause its electronsmove freely.

Jupiter’s Magnetosphere

• Jupiter’s strong magnetic field gives it an enormousmagnetosphere.

• Gases escaping Io feed the donut-shaped Io torus.

Aurora on Jupiter

What is the structure of Jupiter like?1. Rocky core, thin atmosphere2. Rocky core, thick atmosphere3. Gaseous on the outside, then liquid hydrogen,

more dense metallic hydrogen, rocky core4. Gaseous on the outside, then liquid hydrogen,

then helium, then the other elements

Jupiter does not have a large metalcore like the Earth. 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 Sun.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 Moons• Some small moons

create gaps withinrings.

Jovian Ring Systems

• All four jovian planets have ring systems.• Others have smaller, darker ring particles than does Saturn.

Why do the jovian planets haverings?

• They formed from dust created in impactson moons orbiting those planets.

How do we know this?

How do we know?

• Rings aren’t leftover from planet formationbecause the particles are too small to havesurvived this long.

• There must be a continuous replacement oftiny particles.

• The most likely source is impacts with thejovian moons.

Ring Formation

• Jovian planets all have rings because theypossess many small moons close-in.

• Impacts on these moons are random.• Saturn’s incredible rings may be an “accident”

of our time.