Moons
Moons
Small Satellites
Earth = 1
Mars = 2
TOTAL=101
Jupiter = 39
Saturn = 30
Uranus =20
Neptune = 8
Pluto = 1
Time to stop counting moons?
Asteroid Eugenia
Galileo
Mission
Galileo Spacecraft
spins 3 rpm
33 orbits and still going ...
The Galilean Satellites
Galilean Satellite Geology
Callisto’s
Cratered
Surface
Zooming in on Callisto’s Craters
Valhalla
MultiRing
Crater
Chain of
craters on
Callisto
Caused by broken up comets
- such as Comet Shoemaker-Levy 9
Ganymede
Ganymede Global
Ganymede landforms
Ganymede’s Varied Geology
Bright Terrain
Fewer craters
Younger
Grooved & folded
Dark Terrain
Many craters
Older
Grooves caused
by expansion of
Ganymede’s
crust
Callisto and
Ganymede
- Heating of Ganymede led
to separation of dense iron
core, surrounded by rock
with thick layer of ice on
top.
- Dark dust has accumulated
on older surfaces of Callisto
and Ganymede, burying
small craters
- Callisto suffered little
heating and remains a
mixture of ice and rock
Europa
Dark Material Seeping
Through Cracks
Ridges, Spots & Smooth Icy Plains
California
San Andreas Fault
Europa
Astypalaea Linea
Zooming in
on Cracks
and Flows
10 km
5 km
50 km
Ice - sometimes it
suddenly cracks,
sometimes it slowly
flows
Europa’s Triple Bands
Europa landforms
Europa landforms
ball o string
San Fran Scale Comparison
Europa’s
young
surface
shows few
craters
Did this impactor crash right
through the ice?
Tyre
High resolution
images show ice
“rafts” - indication
of thin ice crust,
liquid ocean below?
Europa
• The interior is mostly rock
covered by a ~150 km layer of
water
• A brittle crust (1-10km
thick) has been disrupted in the
past 10 million years by
underlying fluid motions
• Does Europa have a liquid
ocean? Could such ocean
contain life?
• Or, is the water layer frozen,
moving slowly, like a glacier?
Freckles
Upwelling Plumes
Bob Pappalardo
Competing Theories
Tidal Cracking
Rick Greenberg
Europa models - 4
Io
3.57 g/cc
Ganymede
1.94 g/cc
Europa
2.97 g/cc
Callisto
1.86 g/cc
Resonance
4 2 1
Tidal Heating
Laplace orbital Resonance
Tidal forces increase strongly closer to Jupiter
•Heat the interior
•Remove water
•Drive volcanic activity
Plumes
discovered
during
navigation
check trying to fit
a circle to
the disk
Discovery
Early volcanoes
Io
300 km
Amirani
Io’s
Volcanoes
& Geysers
Pilan Plume
Prometheus
Pilan 5 months apart
Pele
IR
After quantities of lava are
removed from below, the crust
cracks and tilts, making tall,
blocky mountains.
11 km high
Hiiaka Patera
Tvashtar
50 km
Io Mtns
Nightside of Io - Visible
Glowing Lava
Plume Gas
& Dust +
Airglow
HST Obervations of Io’s SO2 Atmosphere
Pressure ~ nanobars = 10-9 Earth atmosphere
Variable ….. with volcanic activity?
Jupiter’s Giant Magnetosphere
Ganymede
Io
Europa
Callisto
1 ton / sec
Plasma Production at Io
Schneider & Trauger
Neutral
Sodium
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Ionized
Sulfur
Io Plasma Torus (Schneider & Trauger)
Cassini UltraViolet Imaging Spectrometer
Larry Esposito, University of Colorado
• UV images of the toroidal cloud of ions at Io’s orbit,
• The S+ and O+ ions are trapped by Jupiter’s magnetic field.
• Jupiter is dark at UV wavelengths.
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Clarke et al.
Aurora
Dusk Distortion?
Polar storms
Main Oval
Io footprint
The Io Aurora
Infrared
Ultraviolet
- energetic particles bombard atmosphere
- ‘wake’ emission extends half way around Jupiter
Cassini Spacecraft
Ulysses
Cassini flyby
Dec. 2000
Pioneers
Voyagers
Galileo
Orbiter
33 orbits
Dec. 1995 to
Oct. 2003
Galileo:
The End Game
Sun
• Must never hit Earth or
Europa
• 3 passes close to Io—to
determine if Io has a magnetic
field
• Hits Jupiter October 2003
100 Rjupiter
Titan - 1.5 bars of N2 atmosphere
Voyager 1 (1981)
HST (1996)
QuickT i me™ and a Y UV 420 codec decom pressor are needed to see t his pict ure.
Triton - See Pluto/Charon
Triton