Jupiter
Introduction
Jupiter is the
fifth planet in the solar
system and is the largest. It is the first of the “gas” planets which do not
have a solid surface. The name Jupiter would have probably originated from
the
Greeks. In Greek mythology Jupiter was Zeus, the king of all gods and the
son of
Cronus (Saturn). Jupiter has 63 moons.
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Exploration
Jupiter has been
visited by 6 spacecrafts. The
very first spacecraft to visit Jupiter was the Pioneer 10. This was followed
by
Pioneer 11, Voyager 1, Voyager 2, Ulysses and Galileo which is even now in
orbit
around Jupiter after 8 years.
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Composition
Since gas planets
do not have a solid surface,
the appearance of the planet will not look the same all around. When you
look at
a gas planet you are actually looking at the planets clouds in it’s
atmosphere.
Jupiter is almost completely composed of hydrogen and helium. In smaller
quantities you may also find water, methane, ammonia and a bit of rock.
Because
the planet is made of gas, the ingredients of the core of the planet are
unknown. If we were to guess, Jupiter would have a rocky core that is the
size
of about 10 to 15 Earths.
Interior and
Exterior
The interior of Jupiter is at a extremely high
pressure
(almost 5800 times the pressure of Earth). This results in the formation of
liquid hydrogen from hydrogen gas. Hydrogen also gains metallic properties
and
is able to conduct electricity. This is the cause of Jupiter’s magnetic
field.
Higher up (where we see the planet) hydrogen is in its normal gaseous
state.
The streaks of color on Jupiter are actually bands of wind.
The
winds can go over 400 mph. The temperature and chemical differences in these
bands are the causes for the color. The light streaks of color are known as
zones and the darker ones are known as belts.
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The Great Red
Spot:
The Great Red Spot is a red oval that is clearly
visible and
has been known for a long time. It is enormous being 12,000 by 25,000 km.
That
is about the size of two Earths. This area is under higher pressure, and is
colder and higher than the rest of the planet. Click here for a
close-up.
Moons
Callisto:
Callisto is one
and the outermost of the Galilean moons. It is the second largest moon of
Jupiter. According to Greek mythology, Callisto liked Zeus and hated Hera.
Hera
got very angry at Callisto and changed her into a bear. Zeus then put
Callisto
who was now a bear into the sky as a constellation called Ursa Major.
Callisto
has a very tenuous atmosphere composed of carbon dioxide.
Fact File
Distance from Jupiter: 1,883,000
km
Diameter: 4,800 km
Mass: 1.0823 kg
Size
and
Contents
Callisto is one of the biggest moons in the solar
system
nearing the size of Mercury. However, its mass is much more different being
only
one third of Mercury’s. Callisto is mainly covered with ice, but as you get
deeper in to the planet, you find more rock. Callisto contains 40% ice and
about
60% of rock or iron.
Surface
Callisto is
the
oldest body to be found in the solar system. It is close to 4 billion years
old
and is heavily cratered. No other body in the solar system is as heavily
cratered as this moon. The bigger and larger craters are surrounded by huge
cracks. These cracks get filled up by flowing ice, but this may take
centuries.
One interesting feature of the landscape is a long line of craters. This was
probably caused by a comet which was sent hurtling by Jupiter towards
Callisto
causing a line of craters when it hit the surface.
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Ganymede:
Ganymede is one of Jupiter’s Galilean moons. It is the
largest of
Jupiter’s moons. In Greek mythology, Ganymede was a very handsome boy whom
Zeus
carried away to be a cup holder for the gods . Ganymede is the largest moon
in
the whole solar system. In diameter, Ganymede is larger than mercury but not
even half as dense as it and so has a much less mass. Pluto is much smaller
than
Ganymede.
Fact File
Distance from
Jupiter:
1,070,000 km
Diameter: 5262 km
Mass: 1.4823 kg
Though
Ganymede is very similar to Earth, having oxygen and lots of water, it
cannot be
inhabited because there isn’t enough of it. Ganymede’s surface is covered by
dozens of craters. This large amount of craters suggests that Ganymede is
about
3 to 3½ billion years old.
Io:
Io
is one of the four Galilean moons of Jupiter. It is the closest Galilean
moon to
Jupiter. In terms of size, the moon is the fourth largest in the whole solar
system. In Greek mythology, Io was yet another one of Zeus’ beloved maidens
whom
he loved. Io surface is normally only about 130K which is not at all hot,
but at
some places the temperature can reach upto 2000K. Just like Ganymede, Io
also
has a weak magnetic field. Io has a very thin atmosphere made up mainly of
sulphur dioxide.
Fact File:
Distance
from
Jupiter: 422,000 km
Diameter: 3630 km
Mass: 8.9322 kg
Volcanoes:
Most terrestrial planets or
moons
have surfaces that are badly damaged by craters. However, Io’s surface is
comparitively very smooth and has very few craters. From this we can make
out
that Io is very young.. One of the most suprising things about Io is the
presence of volcanoes. Io has hundreds of volcanoes that are continously
coming
up, erupting and dying.
Features:
Io’s
surface has a wide range of features. It has lots of mountains and
volcanoes. It
also has many lakes that are filled with liquid sulphur. Io, unlike the
other
Galilean moons has very little water. Io may have been very hot in the past
because it is the closest of the Galilean moons to Jupiter and hence it has
very
little water.
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Europa is one of Jupiter’s Galilean moons. It is the fourth largest moon of Jupiter and is fairly small being a bit smaller than our own moon. In Greek mythology, Europa was a Phoenician princess who was kidnapped by Zeus to an area called Crete. Europa is mainly covered by a sheet of ice. It is made up of rock. Unlike the other terrestrial planets which have very jagged landscapes, Europa has a very smooth and featureless landscape.
Craters
There are very few craters on Europa; only three craters larger than 5 km in diameter have been found. This would seem to indicate a young and active surface. However, the Voyagers mapped only a fraction of the surface at high resolution. The precise age of Europa's surface is an open question.
Water
The images of Europa's surface strongly resemble images of sea ice on Earth. It is possible that beneath Europa's surface ice there is a layer of liquid water, perhaps as much as 50 km deep, kept liquid by tidally generated heat. If so, it would be the only place in the solar system besides Earth where liquid water exists in significant quantities.
Dark Streaks
Europa's most striking aspect is a series of dark streaks crisscrossing the entire globe. The larger ones are roughly 20 km across with diffuse outer edges and a central band of lighter material. The latest theory of their origin is that they are produced by a series of volcanic eruptions or geysers.
Did You Know?
1.
Jupiter has 63
moons.
2. Jupiter’s mass is twice of the mass of all the other
planets
combined!
3. Jupiter has rings, but they are extremely faint and
almost
unnoticeable. They are very dark and seem to be composed of bits of rock.
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