Download The Jovian Planets

The Jovian Planets
Exploration of the Jovian Planets
The outer planets have been visited by several
spacecraft, but only two have stayed in orbit:
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Pioneer 10 and 11 visited Jupiter and Saturn,
Voyager 1 and 2 visited all 4 jovian planets,
the Ulysses solar mission, flyby of Jupiter,
Galileo orbited Jupiter, 1995-2003
Cassini flyby of Jupiter, Saturn orbit since 2004,
New Horizons flyby of Jupiter, en route to Pluto
Each of these missions has provided information
about the planets, their moons, and rings.
Terrestrial vs. Jovian Planets
Terrestrial vs. Jovian Planets
Density of terrestrial worlds (3.3 – 5.5 grams per cm3)
indicate they are made of rock and metal.
Density of jovian planets (0.7 – 1.6 grams per cm3)
indicate they are made of lower density stuff.
Current models of the jovian interiors start with a
small core of rock and metal at the center.
On top of that is a thick atmosphere of hydrogen
and helium gas.
The thick atmospheres of the jovian planets mean
they have no solid surface.
Internal Structure
Lower layers inside an atmosphere must support
the weight of the upper layers.
Locations deeper inside an atmosphere must have
larger pressures & higher temperatures to support
the upper layers.
Internal Structure
Due to their enormous sizes, the pressures inside
Jupiter and Saturn are so high that hydrogen is
squeezed into a liquid and hydrogen compounds
(CH4, NH3, H2O) are squeezed into solids (“ices”).
Jupiter’s Internal Structure
Jupiter’s density tells us
about the interior.
Laboratory studies of H &
He tell us how gases
behave under high
pressure.
Computer models predict
pressure & temperature.
Uranus & Neptune
Uranus & Neptune are essentially twins. They have
nearly the same mass and composition.
They both formed far from the Sun where ices were
very common, so their cores are rich in ices.
They probably grew slowly since collisions would
be slower and less frequent that far from the Sun.
It is thought that they didn’t gather as much gas as
Jupiter and Saturn.
So they are mostly core with “thin” atmospheres.
The Ice Giants: Uranus & Neptune
Uranus & Neptune are more ice and rock than gas.
Astronomers call them “ice giants” to divide them
from Jupiter & Saturn, which are mostly H & He.
Which of the jovian planets have solid surfaces?
A. Jupiter & Saturn
B. Uranus & Neptune
C. All four planets
D. None of them
Magnetic Fields
The recipe for a magnetic field, dynamo theory:
1. Fast rotation
2. Interior filled with electrically conducting fluid
3. Hot interior that undergoes convection
Observations:
1. All 4 jovian planets rotate in less than 20 hours
2. Jupiter & Saturn contain metallic hydrogen
3. All 4 jovian planets have hot interiors
Magnetic Fields
Jupiter: strongest
magnetic field of any
planet, 20000x Earth
Saturn: 600x Earth,
less metallic H, less
magnetic field
Uranus & Neptune: no
metallic hydrogen,
but both have fields
about 50x Earth’s
Magnetospheres
The fields of Earth, Jupiter, and Saturn are aligned
with their rotation axes and centered in the cores.
The fields of Uranus & Neptune are neither aligned
nor centered in the core: generated by oceans?
Auroras on Jupiter & Saturn
The Atmosphere of Jupiter
The atmosphere has
very high speed winds
and hurricane-like
activity, shown here in
a movie recorded by
Voyager 1 in 1979.
One frame was taken
each time the Great
Red Spot was visible.
The Atmosphere of Jupiter
The largest circular
feature in Jupiter’s
atmosphere is the
Great Red Spot.
First observed in 1643.
This single storm
could easily hold
several Earths.
Storms A’Plenty
There are no storms in Earth’s atmosphere that
last for several centuries.
An ongoing topic of Jupiter research is how the
planet’s storms keep going for so long.
This Cassini movie shows Jupiter unrolled.
Saturn’s Atmosphere
Storms are visible on Saturn, but they are far less
colorful and much shorter lived.
New infrared observations of storms at Saturn’s
poles is reviving interest in Saturn’s atmosphere.
The Atmosphere of Uranus
Uranus’ unusual heating from the Sun may play a
role in its “blank” atmosphere. Seasonal changes
may produce formation of clouds or storms.
Voyager 2 flyby images (1986)
showed no clouds or storms.
(Left) natural color,
(Right) enhanced color
showing haze over pole.
Hubble Space
Telescope
images (1999)
The Atmosphere of Neptune
During its 1989 flyby, Voyager 2 found a Great Dark
Spot that appeared to be similar to Jupiter’s Great
Red Spot. By the late 1990’s, the spot was gone.
Faster Rotation, Complex Winds
The jovian planets rotate faster than Earth so it is
not surprising that the wind patterns are complex.
Winds in the zones and belts blow in opposite
directions, at 100-1000 kilometers per hour!
Atmospheres: Jupiter vs. Saturn
Saturn’s atmosphere is cooler and under lower
pressure, so thicker, deeper cloud layers.
Jupiter’s clouds are thin, so
we can see several layers.
Terrestrial planets and jovian planets do share
some features. Which of the following Earthly
feature is not present in/on the jovian planets?
A. rotating cyclonic storms like hurricanes
B. cores of high temperature metal
C. volcanoes, plate tectonics, and impact craters
D. magnetic fields that extend into space