Europa
Phoenician
from to
Io stay
– abducted
Callisto––aanoble
nymph
of Artemisdescended
(Diana) vowed
a
by
Zeusbut
in the
form of
whitedisguised
bull and taken
to Crete
virgin,
seduced
byaZeus
as Artemis
and
transformed into a bear – almost slain by her son, Arcas,
but placed among the stars to become a constellation
Ganymede
– Trojan
the most
attractive of mortals
Io
– Priestess
of Heraprince,
– seduced
by Zeus
– abducted by Zeus to serve as cup bearer to the Gods
Jupiter’s Satellites
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What the Galilean satellites are and how
they orbit Jupiter
The similarities and differences among the
Galilean satellites
How the Galilean satellites formed
How tidal forces and synchronous orbits
affect the Galilean satellites
Jupiter’s Satellites
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Why Io is the most volcanically active world
in the solar system
How Io interacts with Jupiter’s magnetic field
The evidence that Europa may have an ocean
beneath its surface
The kinds of geologic activity found on
Ganymede and Callisto
Why most of Jupiter’s moons orbit in the
“wrong” direction
Orbits of the Galilean Satellites
Radius (RJ): Period (days):
Io
Europa
Ganymede
Callisto
5.9
9.4
15
26.3
1
2
4
9.43
What is the relationship between the
orbital periods of the four Galilean
satellites of Jupiter?
A. 1:2:4:8— Europa orbits Jupiter twice,
Ganymede orbits four times and Callisto orbits
eight times during one Io orbit.
B. 1:2—Europa takes twice as long to orbit Jupiter
as Io, but there is no integer relationship
between Callisto and Ganymede with the inner
two Galilean moons.
C. 1:2:4—Io orbits Jupiter four times and Europa
orbits twice during one Ganymede orbit, but
there is no integer relationship between Callisto
and any of the other Galilean moons.
D. The periods appear to be random, with no
simple relationship between them.
Relative Sizes and Distances
from Jupiter
Voyager 1—February 1979
Formation of Galilean Satellites
Protosun “ice-limit”
Proto-Jupiter “ice limit”
Formation of Galilean Satellites
Voyager Mosaic Image
Except for these areas–not seen by Voyager
Io Anomaly Discovery—
Voyager 1 March 8,1979
What’s this?
…an unknown
moon behind
Io???
No!
Galileo composite Image—1996
Side of Io facing Jupiter
Galileo Spacecraft 1996
Galileo—November 1997
Tvashtar Plume—New Horizons,
Feb 28, 2007
Lava Flow from Tvashtar 2000
Change in Lava Flow from Tvashtar
1999-2000
Eruption from Pillan Patera
after several months
The source of intense heating in the interior
of Jupiter's moon Io, causing continuous
and intense volcanic activity, is ______.
A.tidal flexing and distortion, caused by
Jupiter and the other large moons.
B.frictional heating as the solar wind
impacts the moon’s surface.
C.a black hole in its core swallowing up
the matter around it causing Io to
slowly contract and heat up.
D.heat released as it continues to shrink
following its formation, converting
gravitational potential energy into
heat.
Ejection of Sulfur from Io’s Volcanoes
Infrared Glow from Active Volcanoes
Interior of Io
• Thin crust of sulfur
and SO2
• Thicker crust and
Mantle of Silicates
• Dense metallic core
Earth-based Infrared Image
Io Torus
5 Million Amps of Current flows between Jupiter and Io!
Europa—Voyager 1 1979
Galileo Sept 19, 2003—False
Color Infrared and Visible
Europa’s Ridges and Jumbled Terrain
Triple Bands
Formed when crust fractures
• Ridges separate and darken
• Water oozes up and freezes when another fracture occurs
Moving Ice Floes in Canadian Arctic
Ice Rafts on Europa
Interior of Europa
The weak and variable magnetic field
on Europa measured by the Galileo
spacecraft is generated by ______.
A.electrical currents in Europa’s
subsurface ocean water, induced by
Jupiter's intense rotating magnetic
field
B.electrical currents flowing between
Europa and Jupiter
C.the motion of molten iron in Europa's
core
D.electrical currents in the liquid metallic
hydrogen in Europa’s core
Ganymede—Side Facing Away from
Jupiter
Grooved Terrain on Ganymede
Plate Tectonics on Ganymede?
Interior of Ganymede
• Ice Crust
• Icy Mantle probably
includes water and
slush zone
• Large mantle of
silicates
• Iron core
Callisto—Galileo, May 2001
Only complete global color image taken by Galileo
Valhalla Basin
• Largest multiringed impact in
solar system
• Lack of craters
<1 km
• Covered with
dark, dusty
material
Interior of Callisto
• Thick Ice Crust
• Water below crust?
• Mantle of rock and
ice
The surfaces of Ganymede and Callisto
appear to consist mostly of ______.
A.an organic polymer-like goo
B.Ice
C.rocks and lava
D.frozen hydrogen and helium
“It's like imagining we'd flown into the solar system the day before
and said … let's explain it in ten minutes. There was Callisto, with
the highest density of craters of any Galilean satellite, the oldest
of the Galilean surfaces, featuring a huge ‘bull's eye’ that is the
largest single contiguous feature seen so far in the solar system.
There was Ganymede, cratered, but also overrun with fault lines
that looked like ‘tire tracks in the desert,’ showing a surface that
‘had laterally slid, faulted and sheared and sheared again, twisted
and torn apart.’ There was Io–the most bizarre–the one that
scientists thought would be most lunar–like, showing a surface
that had apparently been cooked, steamed and fumed out leaving
deposits all over the surface like you might see around a fumarole
at Yellowstone. It makes it likely that Io is still volcanically active.
There was Europa, with huge linear features unlike those of the
other three Galileans–Europa the mystery satellite, waiting for the
probing eyes of Voyager 2 to survey it in early July.
Ed Stone summed it all up, "I think we have had almost a
decade's worth of discovery in this two-week period … ."
Key Ideas
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Nature of the Galilean Satellites: The four Galilean
satellites orbit Jupiter in the plane of its equator… all in
synchronous rotation.
The orbital periods of Io, Europa, and Ganymede are in
the ratio 1:2:4.
The two innermost Galilean satellites, Io and Europa,
have roughly the same size and density as our Moon.
They are composed principally of rocky material.
The two outermost Galilean satellites, Ganymede and
Callisto, are roughly the size of Mercury. Lower in density
than either the Moon or Mercury, they are made of
roughly equal parts ice and rock.
The Galilean satellites probably formed in a similar
fashion to our solar system but on a smaller scale.
Key Ideas
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

Io: Io is covered with a colorful layer of sulfur
compounds deposited by frequent explosive eruptions
from volcanic vents. These eruptions resemble terrestrial
geysers.
The energy to heat Io’s interior and produce the
satellite’s volcanic activity comes from tidal forces that
flex the satellite. This tidal flexing is aided by the 1:2:4
ratio of orbital periods among the inner three Galilean
satellites.
The Io torus is a ring of electrically charged particles
circling Jupiter at the distance of Io’s orbit. Interactions
between this ring and Jupiter’s magnetic field produce
strong radio emissions. Io may also have a magnetic
field of its own.
Key Ideas
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
Europa: While composed primarily of rock,
Europa is covered with a smooth layer of
water ice.
The surface has hardly any craters, indicating a
geologically active history. Other indications
are a worldwide network of long cracks and
ice rafts that indicate a subsurface layer of
liquid water or soft ice. As for Io, tidal
heating is responsible for Europa’s internal
heat.
An ocean probably lies beneath Europa’s
frozen surface. Minerals dissolved in this ocean
may explain Europa’s induced magnetic field.
Key Ideas
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Ganymede: Two types of terrain are found on
the icy surface of Ganymede: areas of dark,
ancient, heavily cratered surface and regions of
heavily grooved, lighter-colored, younger terrain.
Ganymede is highly differentiated, and probably
has a metallic core. It has a surprisingly strong
magnetic field and a magnetosphere of its own.
While there is at present little tidal heating of
Ganymede, it may have been heated in this
fashion in the past. An induced magnetic field
suggests that it, too, has a layer of liquid water
beneath the surface.
Key Ideas
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
Callisto: Callisto has a heavily cratered crust of
water ice. The surface shows little sign of
geologic activity, because there was never any
significant tidal heating of Callisto. However,
some unknown processes have erased the
smallest craters and blanketed the surface
with a dark, dusty substance.
Magnetic field data seem to suggest that
Callisto has a shallow subsurface ocean.
Key Ideas
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
Other Satellites: As of 2006, Jupiter has a total
of 63 known satellites.
In addition to the Galilean satellites, Jupiter has
four small inner satellites that lie inside Io’s orbit.
Like the Galilean satellites, these orbit in the
plane of Jupiter’s equator.
The remaining satellites are small and move in
much larger orbits that are noticeably inclined to
the plane of Jupiter’s equator. Many of these
orbit in the direction opposite to Jupiter’s
rotation.