Saturn: Moons: Titan
Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan
is the biggest of the 47 known moons orbiting
Saturn. It is a cold world enclosed by a thick, hazy atmosphere
impenetrable by telescopes and cameras.
With an equatorial radius of 2,575 kilometers (1,600 miles), Titan is the
second largest moon in our solar system. It's bigger than our own
moon and even the planet
Mercury. Only
Jupiter's moon
Ganymede is larger than Titan, with a diameter barely
112 kilometers (62 miles) greater.
The temperature at Titan's surface is about minus 178°C (minus
289°F).
Titan orbits Saturn at a distance of about 1.2 million kilometers
(745,000 miles), taking almost 16 days to complete a full orbit - 15.94
days to be exact.
Titan is of great interest to scientists because it is the only moon
in the solar system known to have clouds and a mysterious, thick,
planet-like atmosphere. In 1980, NASA's
Voyager 1 spacecraft tried to take
close up images of the natural features of Titan's landscape but was
unable to penetrate the thick clouds. Instead, the images showed only
slight color and brightness variations in the atmosphere. Titan's
atmospheric pressure is about 60 percent greater than
Earth's -
roughly the same pressure found at the bottom of a swimming pool.
In 1994, NASA's Hubble Space Telescope recorded pictures of Titan,
which suggested that a huge bright "continent" exists on the hemisphere
that faces forward in orbit. These Hubble results don't prove that
liquid "seas" exist, however; only that Titan has large bright and dark
regions on its surface.
NASA's
Cassini-Huygens spacecraft (currently orbiting Saturn) should
shed new light on Titan's mysteries. The spacecraft's instruments are
designed to reveal many of Titan's characteristics. During dozens of
flybys, the Cassini orbiter will map Titan with cloud-penetrating radar
and collect atmospheric data. The Huygens probe will dive through
Titan's dense atmosphere with instruments capable of analyzing its
components.
Combined with the "big picture" information that the Cassini orbiter
will collect during Titan flybys, data from the Huygens probe will
provide scientists with critical information that may shed light on
ancient questions such as "Where did we come from?" And, "How did the
planets form?"
Because of the extremely cold temperatures typical of celestial
bodies that are that far away from the Sun, the structure of Titan's
chemical atmosphere is in a state of deep freeze. It is this chemical
composition that interests scientists a great deal because Titan's
atmosphere might consist of compounds similar to those present in the
primordial days of the Earth's atmosphere. Titan's thick cloudy
atmosphere is mostly nitrogen, like Earth's, but may contain much
higher percentages of "smog-like" chemicals such as methane and ethane.
The smog may be so thick that it actually rains "gasoline-like"
liquids. The organic nature of some of the chemicals found in Titan's
atmosphere might indicate that this fascinating moon could harbor some
form of life.
Titan in Mythology
A generic name for the children of Ouranos and Gaia.
In the Orphic version, the Titans are the ancestors of the
human race. The Titans devoured the limbs of Dionysus,
the son of Zeus, who intended the child to have dominion
over the world. Enraged, Zeus struck the Titans with
lightning. The fire burned them to ashes, and from the
ashes man was formed.
