- Origin of name: From the king
of the gods, Zeus or Jupiter.
- Orbit: Radius 5.20 AU [period
11.9 yr, eccentricity 0.05].
- Viewing: From Earth can see
a few moons and cloud bands; from space, its moons look like
a complex miniature solar system.
- Size: 11.2 Earth
radii, containing 318 Earth masses, or 0.1% of the Sun's mass [its
surface gravity is 2.64 times the Earth's]; Jupiter is
the largest planet, and has more mass than all the others together,
but it is not very dense.
- Rotation: Differential, fast
(one full rotation takes about 10 hours) and bulge.
- Early fly-bys: Pioneer 10 (with
plaque) and 11 in 1973-1974, now leaving the Solar System [possibly detecting
extra forces?]; Voyager 1 and 2 in 1979, also on their way out, and
still functioning; Ulysses in 1992, while on a gravity assist
toward the Sun.
- Recent: The Galileo spacecraft
was in orbit 1995-2003 (and then plunged into the planet); The
Cassini spacecraft flew by in 2000 on its way to Saturn.
- Future plans: A Jupiter
Icy Moons Orbiter had been planned but was cancelled; The Juno mission
is currently planned for 2011; Possible future landers and exploration
of the moons, especially under Europa's icy crust.
Atmosphere and Interior
- Composition: Mostly H2 (70%),
some He; little H2O; The average
density is only 1.3 times that of water.
- General appearance: Circulating,
global cloud bands, with darker, rising "belts" and
lighter, sinking "zones".
- Specific features: Great Red
Spot (a thunderstorm larger than Earth due to a changing high
pressure region, at least 300 years old, but may be shrinking
over many years), Great Dark Spot (at least as large, near the
North Pole), and many smaller spots; Powered by internal heat
and the Sun (the Earth might have them too, if the Sun's energy
was not dissipated by turbulence and friction); [the polar regions
have auroras like Earth, but with additional satellite footprints!]
- Colors: Turbulent and changing,
complex cloud chemistry of white zones and dark belts (methane,
ammonia, sulfur and phosphorus compounds).
- Core: Jupiter may have
a "small" rocky core or none; Most of its heavy elements
are mixed with the rest.
- Energy: Jupiter emits more than
it receives, and was even brighter in the past! Why?
- Magnetic field: 20,000 times
stronger than Earth's; Filled with energetic charged particles
emitting radio waves; Deformed by the solar wind, has a long
tail extending beyond the orbit of Saturn!
- Rings: Thin, made of rock fragments
and dust, unstable and constantly resupplied; They were not expected,
but were seen by Voyager I; Located inside the moons' orbits;
Galilean Moons: Jupiter's
- Overview: The ones that Galileo
saw; From Earth, they appear to be aligned; Why?
- Io: R & mass like
our Moon; Smooth, colored; Active volcanoes, more than 300 [including
Loki, with a lava flow the size of Connecticut] and tall mountains;
In constant geological
activity from tidal stress heating, leaves a trail of plasma
along its orbit, shoots ash and dust like bullets into space.
- Europa: Surface of cracked ice,
with few craters (also very thin oxygen atmosphere); There may
be water underneath! Could life have developed there?
A probe to look under the crust is being planned.
- Ganymede: Largest moon in the
solar system, larger than Mercury! Cratered and ridged surface,
shaped by tectonic forces, criss-crossed with surprisingly smooth
tracts, maybe deep trenches that were later filled with ice;
1:2:4 resonance with Io and Europa.
- Callisto: Similar to Ganymede
(will be resonant in a few hundred million years...).
- Overview: Total = 63 so far
known (as of 2004), far more than any other planet; and there
may be more.
- Inner: Metis, Adrastea, Amalthea
(one of the most unusual moons in the Solar System, because it
gives off more heat than it receives from the Sun), Thebe; rotating
synchronously with their orbit.
- Outer: Leda, Himalia, Lysithea,
Elara; Ananke, Carme, Pasiphae, Sinope; ... many unnamed.
- Origin: Some are probably captured
asteroids, or groups of asteroid fragments from collisions with
other moons; many are on tilted, eccentric and retrograde orbits;
some are as small as 1 km across.
- Big events: 1994, The plunging
of (pieces from) comet Shoemaker-Levy 9 into the planet; 2006, The
appearance of Red Jr and its close encounter with the Great red Spot.
- Puzzle: Pulsating X-rays coming
every 45 minutes from the polar regions.
page by luca bombelli <bombelli at olemiss.edu>,
modified 29 sep 2012