Transcript Orbit Speed (km/sec)

The Jovian
Moons
Jupiter has 16 moons. By
far the largest and best
known are the 4 Galilean
Moons, so named because
they were discovered by
Galileo
IO
After Io's romance with Jupiter, she
was turned into a heifer, pursued by
Juno's gadfly
There are no impact craters on Io.
The surface of Io must be younger
than a Million years old, and is
continually being resurfaced by
volcanic activity.
The surface composition on Io
consists largely of sulfur with
deposits of frozen sulfur
dioxide. The surface on Io is
mostly flat plains rising no
more than 1 km. Moutain
ranges up to 9 km high have
also been observed.
Io is the most active object geologically in the Solar System
It is covered
with volcanic
activity that
spews
various
sulfur
compounds
onto the
surface and
accounts for
the color and
pocked
nature of
the surface
This volcanic activity
does not originate in
plate tectonic
activity the way that
much volcanic
activity originates on
the Earth. Its cause
are the tidal forces
associated with the
500 pound gorilla
next door (Jupiter)
In 1979 an engineer responsible for navigation of
the Voyager I spacecraft noticed a strange
mushroom-like object on the limb of Io
It was realized that
the camera had
captured a volcano
erupting on the
surface of Io, the
first live volcano
found in the Solar
System beyond the
Earth
The Io Plasma Torus
A torus of sodium gas along with sulfur ions is spread out
over Io's orbit. This torus is so large that it has been
observed from Earth. As Jupiter rotates, it takes its
magnetic field around with it, sweeping past Io and
stripping off about 1,000 kilograms (1 ton) of Io's material
every second! This material becomes ionized in the
magnetic field and forms a doughnut-shaped cloud of
intense radiation referred to as a plasma torus. Some of
the ions are pulled into Jupiter's atmosphere along the
magnetic lines of force and create auroras in the planet's
upper atmosphere. It is the ions escaping from this torus
that inflate Jupiter's magnetosphere to over twice the size
we would expect.
Discovery:
Jan 7, 1610 by Galileo Galilei
Diameter (km):
3,630
Mass (kg):
8.94x1022
Orbital period (days):
1.769138
Rotational period (days):
1.769138
Density (gm/cm3)
3.57
Orbit Speed (km/sec):
17.34
Surface Composition:
Sulphur
EUROPA
To elude the ever-watchful Juno,
Jupiter approached Europa as a
bull; she climbed upon his back,
and the two swam off to Crete,
where Europa became an object of
worship
Discovery:
Jan 7, 1610 by Galileo Galilei
Diameter (km):
3,138
Mass (kg):
4.8e22
Orbital period (days):
3.551181
Rotational period (days):
3.551181
Density (gm/cm3)
3.01
Surface Composition:
Water Ice
Orbit Speed (km/sec):
13.74
The United States sent two
spacecraft, Pioneer 10 and 11, to
Jupiter in the early 1970's.
The twin Voyager spacecraft
flew by Jupiter and its moons
in 1979, giving us our first
close-up view of Europa.
Galileo images hint at the
possibility of liquid water
beneath the icy crust of this
moon. The bright white and
bluish parts of Europa's
surface are composed almost
completely of water ice. In
contrast, the brownish
mottled regions on the right
side of the image may be
covered by salts (such as
hydrated magnesium-sulfate)
and an unknown red
component. The yellowish
mottled terrain on the left
side of the image is caused
by some other, unknown
contaminant.
Long cracks run for thousands of kilometers over the surface. On
Earth, these cracks would indicate such features as tall mountains and
deep canyons. But none of these features are higher than a few
kilometers on Europa, making it one of the smoothest objects in our
Solar System
Europa is heated by tidal forces from
Jupiter. The surface bends and flexes
and water gushes to the surface and
freezes
Europa is further from Jupiter
than Io, so the tidal effect is
less dramatic. In the case of
Europa, the effect of the tides
induced by Jupiter is to heat
the interior of Europa
sufficiently to keep the
surface soft. Thus, no vertical
relief features can survive for
long on Europa's surface,
explaining its smooth
appearance.
WHAT DO YOU THINK?
GANYMEDE
Ganymede, a "handsome youth" attracted Jupiter's
attention too, who whisked the boy off to become a
cupbearer to the gods
Zeus, made a place for
him among the stars as
Aquarius – the Water
Bearer. There he still
stands, smiling, pouring
nectar and shielded to
this day by the wing of
the Eagle
constellation.
Ganymede is larger than the planet Mercury but only half
its mass. It is the largest Jovian satellite, and the largest
moon in the solar system
Its diameter is 5270 km, much larger than
our own Moon (3476 kilometers).
Ganymede is
the third of
the Galilean
moons
Bright frost is visible at the north and
south poles. The very bright icy impact
crater, Tros, is near the center of the
image in a region known as Phrygia
Sulcus. The dark area to the northwest
of Tros is Perrine Regio; the dark
terrain to the south and southeast is
Nicholson Regio.
Ganymede's
surface is
characterized by a
high degree of
crustal deformation
Ganymede's surface is a roughly equal mix of two types of
terrain: very old, highly cratered dark regions (left), and
somewhat younger (but still ancient) lighter regions marked
with an extensive array of grooves and ridges (right). Their
origin is clearly of a tectonic nature, but the details are
unknown. In this respect, Ganymede may be more similar to the
Earth than either Venus or Mars (though there is no evidence
of recent tectonic activity).
The brownish-gray color
is believed due to
mixtures of rocky
materials and ice.
Geologically recent
impact craters and
their ejecta are
indicated by bright
regions
New and old terrain
The structure of Ganymede
Ganymede is composed of silicate rock and water ice, with
an ice crust floating over a slushy mantle that may
contain a layer of liquid water
Preliminary indications
from the Galileo probe
data suggest that
Ganymede is
differentiated into a
three layer structure: a
small molten iron or
iron/sulfur core
surrounded by a rocky
silicate mantle with a
icy shell on top.
CALLISTO
The Galilean satellites are all named
after objects of mythological
Jupiter's wide-ranging fancies.
Callisto was a beautiful maiden who
enticed Jupiter, thereby invoking the
wrath of Juno, Jupiter's wife. She
turned Callisto into a bear
Callisto and her son
Arcas transformed as
the Great Bear and
the Bear Warden.
(c) 1995 Visula
Language. All rights
reserved.
With a diameter of over 4,800 km (2,985 miles),
Callisto is the third largest satellite in the solar
system and is almost the size of Mercury
Discovery:
Jan 7, 1610 by Galileo Galilei
Orbit Speed (km/sec):
8.21
Mass (kg):
1.077e23
Rotational period (days):
16.68902
Orbital period (days):
16.68902
Callisto is the outermost of the Galilean satellites,
and orbits beyonds Jupiter's main radiation belts.
It has the lowest density of the Galilean satellites
(1.86 grams/cubic centimeter).
Callisto is also made of ice and is heavily
cratered. It is the least reflective of the
four, but brighter than our moon. It is hard
to see from Earth. The surface temperature
on Callisto varies from a high of -118° F to a
low of -193°.
Callisto is the most heavily
cratered object in the solar
system. It is thought to be a
long dead world, with a
nearly complete absence of
any geologic activity on its
surface. In fact, Callisto is
the only body greater than
1000 km in diameter in the
solar system that has shown
no signs of undergoing any
extensive resurfacing since
impacts have molded its
surface. With a surface age
of about 4 billion years,
Callisto has the oldest
landscape in the solar
system.
The large Valhalla multi-ring structure
(visible near the center of the image)
has a diameter of about 4,000
kilometers, making it one of the
largest impact features in the Solar
System
It is only weakly influenced by Jupiter-induced tides. The
evidence suggests that the crust of Callisto probably froze as it
was formed, and essentially nothing has happened geologically on
Callisto for 4.5 billion years except for the influence of large
and small meteor impacts.
The Other Moons
of Jupiter
Jupiter has a dozen moons other than the large Galilean
satellites. These are much smaller than the Galilean moons
University of Hawaii astronomers announce the discovery of 11
new satellites of Jupiter. These new satellites, when added to
the eleven discovered the previous year by the Hawaii team,
bring the total of known Jupiter satellites to 39. Jupiter now
has more known satellites than any other planet.
The new
satellites were
discovered
during midDecember of
2001
http://antwrp.gsfc.nasa.gov/apod/ap010102.html
http://www.resa.net/nasa/callisto.htm
http://csep10.phys.utk.edu/astr161/lect/jovian_moons/jovian_moons.html