Page 311 - NS-2 Textbook

306 NAUTICAL SCIENCES

southern hemisphere. The Red Spot is some 17,000 miles time before 2010, and a possible mission to send a sub-
long by 8,500 miles wide. It drifts slowly around the marine probe to Europa to burrow through the ice and
planet, staying generally in the same latitude. Its color look for life underneath.
sometimes fades to a gray and then returns to its red-or- Undoubtedly, many more amazing discoveries about
ange state. Some scientists think the Red Spot is a long- Jupiter and its moons aV\Tait in years to come.
lived storm that will eventually disappear. Others think
that it is a concentration of methane, anunonia, and hy-
drogen-the characteristic gases of Earth's earliest
SATURN
ahnosphere.
In October 1989 the Gali/eo spacecraft was launched Named for the Roman god of time, the beautiful ringed
from the space shuttle Atlantis with a dual mission to planet Sahlm is the solar system's second-largest planet.
launch an exploratory probe into the Jovian ahnosphere SahU'n's rings are made up of billions of tiny solid parti-
and thence to orbit the planet for at least two years in cles. They extend outward from 7,000 miles to 171,000
order to conduct an extensive survey of the planet and miles above the planet's surface. They are on the plane of
its four major moons, called the Galilean satellites in the planet's equator, tipped to the orbit at an angle of 26.8
honor of their discoverer. While on its way it passed degrees. The rings rotate about the planet, the inside ring
near the asteroid belt, close enough to get detailed pic- moving at a faster speed than the outer ones.
hues of two asteroids, and discover a small moon orbit- It is believed that Saturn's interior is composed of a
ing around one of them. In July 1994 another spectacu- core of rock covered by a mantle of ice. This in turn is
lar series of pictures was made of the impact on Jupiter surrounded by a dense ahnosphere of compressed hy-
of fragments of comet Shoemaker-Levy. Huge fireballs drogen, topped with clouds of methane and anunonia.
and plumes of dust and gas were observed, followed by At 886 million miles from the Sun, Saturn has extremely
black and brown discolorations, some of which were as low temperatures. It is probable that there is no solid sur-
large as planet Earth. face for thousmds of miles under the cloud layers. In this
Galileo entered orbit around Jupiter in December respect, Saturn may be quite slmilm' to Jupiter.
1995, the same day as its probe released months earlier The Piolleer 11 spacecraft that flew by Jupiter in late
slammed into the Jovian ahnosphere at a speed of about 1973 was redirected to make a flyby of Saturn in Septem-
106,000 miles per hour (47 kilometers per second). The ber 1979, while Piolleer 10 continued outbOWld. There
probe incorporated experiments to measure temperature ,vas some concern that its instruments would not con-
and pressure along the descent path, locate major cloud tinue to function for the Saturn encounter, as they had
decks, and analyze the chemistry of ahnospheric gases. been designed to last only for ilie Jupiter mission, but in
TIle probe also attempted to detect and study Jovian the end most worked perfectly, and continued to do so
lightning both by looking for optical flashes and by lis- for years thereafter.
tening for the radio static they generate. It traveled to be- The two more capable Voyager spacecraft flew by
tween 130 and 160 kilometers below Jupiter's cloud tops Saturn md several of its moons in late 1980 md August
before the extreme ahnospheric pressure there rendered 1981. A tremendous amount of new knowledge about
it inoperable. the plmet, its rings, md its moons was gained as a result,
Although Gali/eo's mission was originally planned including dozens of spectacular high-resolution color
to last only two years, it ultimately explored Jupiter and pictures.
its moons for a total of eight years until it was sent on a The total of all the data on Saturn gailiered by Piolleer
final plunge into the Jovian ahnosphere in September 11, Voyager 1, md Voyager 2 has revealed that Sahu'n is a
2003. Many new discoveries about Jupiter and its moons planetary system unlike any other in our solar system. In-
were made by Gali/eo and its probe. Particularly intrigu- deed, with its multiple rings and some thirty known
ing was the discovery that liquid water probably exists satellites, Saturn is a kind of solar system in miniature. It
beneath the moon Europa's icy surface. The moon ap- displays many of the fund31llental physical processes
pears to be covered by a layer of ice about 12 miles thick connected with the formation and early evolution of our
over most of its surface, and calculations based on planetmy system. The continued Shldy of Saturn may
GaWeo's data indicate there may be a 65-mile deep ocean shed much light on how the solm' system was formed.
beneath the ice, kept in liquid form by energy from the The exploration of Saturn by the Pioneer md Voyager
gravitational pulls of the planet plus its other moons. In- spacecraft is considered to be among the greatest achieve-
dications are that this ocean nlay have all the elements ments of science in the last cenhuy.
necessmy to harbor life in some form, at least at the FollOWing their enCOlmters with Sahu'n, Voyager 1
microbial level. This possibility has excited scientists continued on a path out of the solar system, and Voyager
and led to planning follow-on missions that include an- 2 was redirected toward eventual flybys of Uranus in
other planetary orbiter called JlIllO to be launched some- January 1986 and Neptune in August 1989. After having