Jupiter Moons

Jupiter, the largest of the Jovian planets, reigns supreme throughout the solar
system. Named after the Roman god Jove, the ruler of Olympus; "Jupiter is
the fifth planet from the sun and is also the largest planet in the Earth\'s
solar system. It is 318 times moremassive than Earth and is two thirds of the
planetary mass in the solar system. Jupiter\'s surface, unlike earth, is gaseous
and not a solid. It is about 90% hydrogen and 10% helium with traces of methane,
ammonia, water and rock. Jupiter\'s interior is very similar to the Sun\'s
interior but with a far lower temperature."(Columbia) However, it is still
unknown for certain, but Jupiter is believed to have a core of liquid metallic
hydrogen. This exotic element can only be achieved at a pressure greater than 4
million bars. Jupiter radiates more energy in space than it receives from the
sun. "Jupiter\'s orbit lies beyond the asteroid belt at a mean distance of
c.483 million mi (773 million km) from the sun; its period of revolution is

11.86 years." (Seeds) In order from the sun it is the first of the Jovian
planets (Jupiter, Saturn, Uranus, and Neptune), very large, massive planets of
relatively low density, having rapid rotation and a thick, opaque atmosphere.
"Jupiter has a diameter of 88,679 mi (142,800 km), more than 11 times that
of the earth. Its mass is 318 times that of the earth and about 2 1/2 times the
mass of allother planets combined." (Columbia) A measurement of the
diameter of Jupiter determined the planet\'s polar flattening. The flattening of

Jupiter was revealed by Pioneer to be slightly greater than that derived from
the best Earth-based measurements. "The diameter of the planet was measured
at a pressure of 800 mbar near the cloud tops (a bar is roughly equal to the
pressure of 1 atm of Earth). Its polar diameter is 133,540 km (82,980 miles) and
its equatorial diameter is142, 796 kilometers (88,732 miles)." (Seeds)

These values were established by the timing of the occultation of the spacecraft
by Jupiter. Thus, Jupiter is nearly 20 times more fattened than Earth,
principally because of its non-solid state and its higher rate of rotation. The
average density of Jupiter, calculated from its mass and volume, was confirmed
as 1.33 gm/cm^3 (the density of water is 1). The atmosphere of Jupiter is
composed mainly of hydrogen, helium, methane, and ammonia. "It appears the
atmosphere is divided into a number of light and dark bands parallel to its
equator and shows a range of complex features, including an ongoing storm called
the Great Red Spot, located in its southern hemisphere and measuring 16,150 mi
long by 8,700 mi wide (26,000 by 14,000 km)." (Columbia) This Great Red

Spot is still present in Jupiter\'s atmosphere, more than 300 years later. It is
now known that it is a vast storm, spinning like a cyclone. Unlike a low-
pressure hurricane in the Caribbean Sea, however, the Red Spot rotates in a
counterclockwise direction in the southern hemisphere, showing that it is a
high-pressure system. "Winds inside this Jovian storm reach speeds of about

270 mph. The Red Spot is the largest known storm in the Solar System. With a
diameter of 15,400 miles, it is almost twice the size of the entire Earth and
one-sixth the diameter of Jupiter itself." (Fimmel) The Great Red Spot was
first detected by Robert Hooke in 1664. Jupiter has no solid rock surface. One
theory pictures a gradual transition from the outer ammonia clouds to a thick
layer of frozen gases and finally to a liquid or solid hydrogen mantle.
"The Spot and other markings of the atmosphere also provide evidence for

Jupiter\'s rapid rotation, which has a period of about 9 hr 55 min. This rotation
causes a polar flattening of over 6%." (Columbia) The temperature of

Jupiter ranges from about -190° F (-124°C) for the visible surface of the
atmosphere, to 9° F (-13° C) at lower cloud levels; localized regions reach as
high as 40° F (4° C) at still lower cloud levels near the equator. Jupiter
radiates about four times as much heat energy as it receives from the sun,
suggesting an internal heat source. This energy is thought to be due in part to
a slow contraction of the planet. Jupiter is also characterized by intense
non-thermal radio emission; in the 15-m range it is the strongest radio source
in the sky. Jupiter has a simple ring system that is composed of an inner halo,
a main ring and a Gossamer ring. To the Voyager spacecraft, the Gossamer ring
appeared to