Download Class 32

ASTRONOMY 202 Spring 2007: Solar System Exploration
Instructor: Dr. David Alexander
Web-site: www.ruf.rice.edu/~dalex/ASTR202_S07
Class 32: Jovian Planets [4/9/07]
Announcements
Jovian Planets
Interiors
Atmosphere
Magnetosphere
Jovian Moons
Chapter 11
Now Playing:
Planetary Rings
Announcements
Homework
HW8 is due NOW
HW9 online tonight due Mon Apr 16
Observing
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Interior Structure
The composition of the cores of all four Jovian planets is expected to be very
similar despite their large range of size and density.
Jupiter and Saturn are large enough to have metallic hydrogen and to have
liquid cores of rock, metal and H compounds.
The cores of Uranus and Neptune are relatively large because they are less
compressed by the surrounding gas.
Jovian Planetary Atmospheres
Like Earth, the Jovian planets have a complicated atmospheric structure,
featuring a troposphere, stratosphere and thermosphere.
The tropospheres are particularly interesting giving a range of dynamic
weather features such as clouds, storms and global wind patterns.
Jupiter’s Cloud Cover
Jovian Weather Systems
Jupiter’s cloud layers are a
result of global wind
patterns, altitude variations
and composition: ammonia
clouds are white, cool and
high while the ammonium
hydrosulphide clouds are
brown, lower and warmer.
Great Red Spot is a
>300 year old
storm which spins
in opposite sense to
what is expected
Other, shorter lived
storms are also
seen.
Great Red Spot
Jupiter’s New Red Spot
The official name of this storm is "Oval BA," but "Red Jr." might be better. It's about
half the size of the famous Great Red Spot and almost exactly the same color.
Oval BA first appeared in the year 2000 when three smaller spots collided and merged.
The oval was white in November 2005, it slowly turned brown in December 2005, and
red a few weeks ago.
Magnetospheres
Each of the Jovian planet’s is
surrounded by a magnetosphere: a
bubble of plasma contained by a
magnetic field generated in the
interior of the planet.
Jupiter’s magnetic field is 20,000
times stronger than the Earth’s
and extends some 3 million km
towards the Sun.
Magnetospheres and the Moons
Volcanic activity on Io populates the
inner regions of Jupiter’s
magnetosphere with a charged
particle belt known as the Io torus.
Ganymede shows signs of a dense
magnetic core and exhibits a strong
magnetic field
Jovian Moons
The Jovian planets have over 100 moons between them. Some of them are
comparable in size to a small planet like Pluto or even Mercury and a number are
larger than the Earth’s Moon.
Saturn’s moon, Titan, has a dense atmosphere while the four Galilean moons of
Jupiter, Io, Europa, Ganymede and Callisto all show interesting geological
behaviour.
Io
Volcanoes
Europa
Ice Geology
Ganymede
Magnetic Field
Callisto
Salty Ocean
Titan
Dense atmosphere
Io : the most volcanically active world in the solar system
Io has so much volcanic activity that no impact craters
are evident.
The outgassing from the volcanoes are the source of the
large amounts of ionized gas (plasma) in Jupiter’s
magnetosphere.
Io loses atmospheric gas faster than any other world in
the solar system.
Volcanic eruptions on Io’s dark side
Tidal heating
Moons like Io are too small and too old to be generating significant amounts of
internal heat so the source of energy for the volcanism on Io has to be due to
something else.
The size and shape of Jupiter together with the closeness and eccentricity of Io’s
orbit provides for internal heating due to tidal forces.
Europa: The Water World?
Europa’s surface and crust
are made almost entirely of
water ice. It also has a
metallic core and a rocky
mantle.
The cracked structure
reveals the presence of tidal
heating and suggests a
liquid ocean some 100 km
thick under the icy crust.
Titan: The Smoggy Moon
Titan has a smoggy atmosphere composed mostly of
Nitrogen (90%), somewhat like the Earth (77%),
with the remainder being made up of Argon,
methane and ethane, making Titan warmer than
expected (-180oC). Titan has a surface pressure only
slightly larger than the Earth’s.
The relatively low proportions of methane and
ethane in the atmosphere suggests that it ‘rained’ out
and may form liquid oceans on the surface. This is
borne out by infrared images of the surface.
Titan may have liquid oceans of methane and ethane topped by a nitrogen atmosphere
Hydrocarbon Lake –
Titan South Pole
High ridge area including the flow down
into a major river channel from
different sources.
Hydrocarbon Lake –
Titan South Pole
Titan volcano?
Enceladus: The stripy moon
Enceladus’ surface has a distinctive
tectonic structure. Its outer
boundary is marked by a series of
pronounced tectonic 'gashes' that
form a hoop-like boundary, near 60
degrees south latitude. In this image,
this fault zone forms the transition
region from the presumably older,
cratered terrain in the north to the
younger, nearly crater-free region in
the south.
Plumes of icy material extend above the southern
polar region of Saturn's moon Enceladus.
Scientists believe that the plumes are geysers
erupting from pressurised sub-surface reservoirs of
liquid water above 273K (0°C).
Planetary Rings
The Jovian planets all display a system of rings comprised of
millions of icy particles ranging in size from dust to boulders.
Ring particles are made mostly of water ice and
are bright where there are enough particles to
scatter sunlight back to us.
Each particle in the rings orbit according to
Kepler’s laws.
The rings of Saturn show a large number of
features
Pan
Cassini Division
Rings and Gaps
Gap Moons
Spokes
Planetary Rings
Uranus
Jupiter
Saturn
Neptune