The Sun and Moon

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Jupiter
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The Gas Giants

• Jupiter, Saturn, Uranus, and Neptune
• much larger masses and lower densities than
  terrestrial planets
• mostly H and He enough gravity to hold onto
  these light atoms
• no solid surfaces atmospheres become hotter,
  denser, and higher pressure with greater depth,
  changing from gas to liquid to solid

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Basic Properties of Jupiter
Diameter 11.2 Dearth Mass 318 Mearth Distance
from Sun 5.2 AU Gravity 2.5 g Atmosphere
H2, He, etc. Temperature varies with
depth Rotational period (its day) 9.9
hours Orbital period (its year) 11.9
years Magnetic field very strong Moons
several dozen
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The View of Jupiter from Earth

• Because Jupiter is so large, telescopes on Earth
  are able to detect features in its atmosphere,
  such as the Great Red Spot.
• Sharper images are provided by Hubble, but as
  with other planets, the most detailed images are
  produced by spacecraft that have visited Jupiter.

ground-based telescope
Hubble Space Telescope
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Missions to Jupiter
Most of our knowledge of the outer planets comes
from space probes. Pioneer 10 (1972) was the
first spacecraft to travel through the asteroid
belt and to visit Jupiter (1973). Pioneer 11
(1973) conducted flybys of both Jupiter (1974)
and Saturn (1979), obtaining a gravity assist
from Jupiter along the way. Both spacecraft are
coasting into deep space and are more than 80 AU
from the Sun. These spacecraft provide the first
close-up pictures of Jupiter, Saturn, and their
moons.
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Missions to Jupiter
Voyager 1 and 2 (1977) took advantage of a rare
planetary alignment that happens only once every
175 years to visit multiple gas giants. Each
spacecraft arrived at Jupiter in 1979 and used a
gravity assist to continue to Saturn in
1980-1981. Voyager 1 then headed out of the solar
system, while Voyager 2 used a gravity assist
from Saturn to travel to Uranus in 1986 and
Neptune in 1989 before continuing out of the
solar system. Both are now about 100 AU from the
Sun.
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Missions to Jupiter
After gravity assists from Earth and Venus,
Galileo (1989) arrived at Jupiter in 1995. Unlike
Pioneer and Voyager, Galileo entered orbited
around Jupiter and studied the planet and its
moons for several years. In 2003, the spacecraft
was nearly out of fuel, which was needed for
adjustments to its orbit. To avoid the
possibility of an impact with Europa and
contamination of this promising site for life,
Galileo was placed on a collision course with
Jupiter.
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Missions to Jupiter
In addition to the orbiter, Galileo included a
probe that was dropped into the atmosphere of
Jupiter. It transmitted data on the temperature,
pressure, and chemical composition for 1 hour as
it descended through 200 km of atmosphere until
it was eventually crushed and destroyed by the
high pressures.
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Missions to Jupiter
The Cassini (1997) spacecraft conducted a flyby
of Jupiter in 2000 during a gravity assist on its
way to Saturn.
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Atmosphere of Jupiter
The clouds in the atmosphere of Jupiter are
complex in appearance. Alternating light and
dark belts are found near the equator while more
mottled clouds appear toward the poles. The
varying structures are caused by differing cloud
heights, thickness, and chemical compositions.
Because of Jupiter's rapid rotation and the
convection of hot gases upward and cool gases
downward, the bands of clouds are constantly
changing and moving.
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Atmosphere of Jupiter
The rapid rotation of Jupiter causes the cloud
layers to move very fast. The velocities of the
layers vary with latitude, which resembles the
differential rotation of the Sun. The belts and
zones are equivalent to high- and low-pressure
systems on Earth. However, because of Jupiter's
rapid differential rotation, these systems wrap
all the way around the planet, instead of forming
localized circulating storms.
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The Great Red Spot
The most distinctive feature of Jupiters
atmosphere is the Great Red Spot, which is a huge
storm that is larger than the Earth.
Observational records indicate that it has
existed continuously in one form or another for
more than 300 years, and it may well be much
older.
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The Great Red Spot
On Earth, hurricanes form over warm ocean water
and may survive for a week, but they dissipate
quickly once they move over land or colder water
and no longer have a source of energy. Jupiter
has no continents, so once a storm is established
and has reached a size at which other storm
systems cannot destroy it, apparently little
affects it. The larger the system, the longer its
lifetime.
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The Colors of Jupiter
This brown oval is a break in the upper cloud
layer, allowing us to see deeper into the
atmosphere to where the clouds are brown. The
oval's length is equal to Earth's
diameter. Trace amounts of sulfur and phosphorus
may play important roles in influencing the cloud
colors, particularly the reds, browns, and
yellows.
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The atmospheric probe launched by Galileo
provided a great deal of new information
concerning the structure of Jupiters atmosphere.
It is quite complex with many layers of varying
composition, pressure, and temperature.
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Internal Structure of Jupiter
The pressure is so high deeper into Jupiter that
hydrogen is compressed to a liquid and eventually
a solid (metal). The core of the planet may be
similar in composition to the Earth, but 10 times
the mass of the Earth.
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Magnetic Field of Jupiter
Helped by its fast rotation, Jupiter generates a
very strong magnetic field. When the solar wind
interacts with the magnetic field, aurora appear
in the upper atmosphere near the poles of
Jupiter, just as on Earth.
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Magnetic Field of Jupiter
In addition to the solar wind, electrical
currents between Jupiter and its larger moons
also account for some of the aurora. Volcanic
eruptions on Io produce charged particles that
flow along the magnetic field of Jupiter down to
Jupiters atmosphere, where they produce a
particularly bright footprint in the aurora.
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Jupiters Rings
In 1979, Voyager 1 discovered faint rings around
Jupiter. They can be seen from Earth only with
large telescopes. These rings are made of dust
that is kicked up from inner moons by meteoroid
impacts. Saturns rings contain more debris and
are made of ice, making them much brighter.
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Impact with Comet Shoemaker-Levy 9
In 1993, the comet Shoemaker-Levy 9 was
discovered near Jupiter. It was the first comet
found in orbit around a planet. At the time of
its discovery, the comet consisted of several
fragments close together, which spread apart over
time. The sizes of the fragments ranged from 0.1
km to 2 km.
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Impact with Comet Shoemaker-Levy 9
After its orbit was measured, astronomers
realized that the comet had been torn apart in
1992 by tidal forces of Jupiter when it passed
with the Roche limit of the planet. And most
importantly, the orbit indicated that the comet
would collide with Jupiter in 1994, which would
be the first impact of a large asteroid or comet
ever witnessed.
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Impact with Comet Shoemaker-Levy 9
More the a dozen fragments collided with Jupiter
between July 16-22, 1994. The impacts occurred on
the night side of the planet, so they were not
directly visible from the Earth, but the impact
sites quickly rotated around into view. The
imprints of the collisions persisted for months.
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Impact with Comet Shoemaker-Levy 9
These chains of craters on the moons Callisto and
Ganymede were probably produced by impacts of
comets like Shoemaker-Levy 9 that were torn apart
by Jupiters tidal forces.
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Jupiters Moons
Galileo drew these sketches after discovering
four moons orbiting Jupiter in 1610. They were
the first moons discovered beyond the Earth and
are Jupiters largest moons. They are called the
Galilean satellites.
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Jupiters Moons
The innermost moon, Io, is the most geologically
active object in the solar system. Volcanoes are
constantly erupting and producing lava flows. As
a result, the surface is smooth and doesn't have
impact craters. This activity is caused by
heating of the interior by Jupiters tidal forces.
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Jupiters Moons
Europa has an icy crust that is heavily
fractured, as indicated by the dark lines across
its surface. These fractures appear to be filled
with a mixture of ice slush and rocks. The outer
shell of ice is about 100 km thick and may be
partially liquid due to warming from Jupiters
tidal forces. An ocean under the crust of Europa
is one of the most promising sites for life
elsewhere in the solar system.
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Jupiters Moons
Ganymede is the largest moon the solar system,
and is even larger than Mercury and Pluto. Darker
areas of the surface are older and are probably
part of the original crust (like the highlands on
the Moon). Lighter regions are younger and were
produced by flooding and freezing of water
brought to the surface by giant impacts (like the
Moons maria). Ganymede also has grooves and
ridges that were probably produced by motions of
crustal plates.
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Jupiters Moons
Callisto similar to Ganymede, except that it is
slightly smaller and is more heavily cratered.
Because it is more distant from Jupiter, it has
experienced less tidal heating and resurfacing.
Although it is colder than Europa and Ganymede,
Callisto may also have an ocean 100 km below the
crust.