20. gas giants

Voyager 2 is the only spacecraft to visit all four outer planets.

Spacecraft to the Outer Solar System

Flybys: Pioneer 10, 11 Voyager 1, 2

Orbiters/ : Galileo, CassiniLanders (Jupiter) (Saturn)

Gas Giant Planets

• Our goals for learning• What are jovian planets like?

• What are the clouds like? (Jupiter as a type example)

What are Jovian planets Like?

Similarities: Ring Systems

• All four jovian planets have ring systems, Saturn merely the most obvious.

• Others have smaller, darker ring particles than Saturn

Rotation and Shape• Jovian planets

are not quite spherical because of their rapid rotation

Similarities: Interiors

• No solid surface. • Layers under high pressure and temperatures.• Strong magnetic fields => conducting materials • Cores (~10 Earth masses) made of hydrogen

compounds, metals & rock• The layers are different for the different planets

due to differences in composition and pressure.

Inside Jupiter (the best understood)

• Inside Jupiter, high pressures cause hydrogen to change phase with depth.

• Hydrogen acts like a metal at great depths because the hydrogen is squeezed until electrons move freely

Inside Jupiter

• Core is thought to be made of rock, with some metals, and hydrogen compounds

• Core is about same size as Earth but 10 times as massive

Subdividing the Gas Giants

Differences: Composition• Jupiter and Saturn

– Mostly H and He gas

• Uranus and Neptune– Mostly hydrogen compounds: water (H2O),

methane (CH4), ammonia (NH3)– Some H, He, and rock

Differences: Interiors

• Models suggest cores of jovian planets have similar composition

• Lower pressures inside Uranus and Neptune mean no metallic hydrogen

What are the Clouds Like?

Colors of The Gas Giants

Colors of the gas giants are temperature controlled

different gasses will form clouds at diff temps.

Colors of The Gas Giants

high thin haze

high haze

thicker clouds .

thick heavy clouds

• Jupiter - high brown and white clouds

• Saturn- bands deeper thicker smog haze

• Uranus -light blue

• Neptune dark blue

•Decreasing temp: increasing methane clouds•Methane clouds reflect blue light

Jupiter

Jupiter’svertical

atmosphericstructure

Different materials form stable ice clouds at different temperatures & pressures

=> different clouds form at different heights

Jupiterconvection

Convection cells create a pattern of white high clouds & brown low clouds

Great Red Spot

-Giant storm

Saturn

Close up of Saturn’s E-W cloud bands

S. Pole of Saturn -Cassini IR

Methane absorbing λs Methane free λs

Uranus

Early Voyager images, taken at southern summer, showed no cloud bands

Earth’s tilt 23½°

Uranus’ tilt 98°

the large axial tilt causes the poles of Uranus receive more sunlight than the equator, during the summer and winter.

Northern Summer

Sun heats the North

pole

Northern Winter Sun heats the South pole

Even heating on both hemispheres

Even heating on both hemispheres

This seriously affects the planet's wind flow during the summer and winter, so that Uranus' clouds appear unusually smooth.

Voyager flew past the south pole during its summer and took very bland images.

This Hubble image shows the Uranus, system, with its ten rings and eight of its moons.

In this false color image, taken in infrared light, the moving bands of cloud show up well.

Uranus

Neptune

© 2014 Pearson Education, Inc.

Surprising discovery or fraud? - Saturn's core is pockmarked with impact craters and dotted

with volcanoes erupting basaltic lava.

A. Plausible. Saturn's moons also show impact craters and volcanoes.

B. Plausible. Saturn's atmosphere originated from the volatiles in impactors that were released via volcanic activity.

C. Implausible. No impactors would survive the immense pressures at the depth of Saturn's core.

D. Implausible. Saturn's high rotation would prevent an impactor from reaching its core.

© 2014 Pearson Education, Inc.

Since there are a lot of flammable gases on Gas Giants, such as methane and propane,

if you lit a match, would Jupiter burn?

A. yesB. no

What have we learned?• What are the clouds like?

– The gas giant planets have different color clouds at different heights due to temperature differences

– They are striped because different clouds are visible due to convection plus rapid rotation causing a strong coriolis effect.