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Old December 13th 03, 12:57 AM
Ron Baalke
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Default Saturn Rings in the New Year


http://science.nasa.gov/headlines/y2...dec_saturn.htm

Saturn Rings in the New Year
NASA Science News
December 12, 2003

Lovely Saturn is going to have a close encounter with Earth this year on
New Year's Eve.

Dec. 12, 2003: When the clock strikes midnight on Dec. 31st, heralding the
start of 2004, dash outside and look up. Directly overhead you'll see a yellow
star outshining the others around it. That star is a planet: Saturn, having its
closest encounter with Earth for the next 29 years.

"Saturn's going to be really beautiful," says NASA astronomer Mitzi Adams. "Not
only will Saturn be about as close to Earth as it can get--748 million miles away--
but also its rings are tipped toward us. Sunlight reflected from
Saturn's rings makes the planet extra bright."

If you have a telescope, advises Adams, be sure to point it at Saturn. Even a small
'scope will reveal the spectacular rings. "They're breathtaking," she says.

2004 is going to be a big year for Saturn. The Cassini-Huygens spacecraft, en
route since 1997, will arrive there in June. Other spacecraft have visited Saturn--
Pioneer 11 and the Voyagers--but they merely flew by, taking hurried pictures during
encounters that lasted little more than days. When Cassini reaches Saturn it will stay,
orbiting and studying the planet for at least four years.

Saturn is a world of great mystery. Consider its rings: Researchers aren't sure what
made them or when. Some evidence suggests that the rings are young--only a few hundred
million years old. If so, they first encircled Saturn at about the same time dinosaurs
took over the Earth. In the cosmic scheme of things, this is recent history.

Saturn's rings might be collapsing just as fast as they formed--so say some theorists.
Small moons orbiting through the outermost regions of the ring system are gaining angular
momentum at the expense of the rings, a result of gravitational interactions between the
moons and chunks of ring-matter. During the next few hundred million years, the outer half
of the rings could sag toward the planet as the little moons (called shepherd satellites)
are flung away. Saturn will look much less impressive after that.

Could it really happen? Cassini will gather the data scientists need to answer that
question and many others about Saturn's rings, moons, weather and magnetism. There's
much to learn about this distant planet.

At least as intriguing as Saturn is its giant moon Titan. "You can see
Titan through a telescope--an 8th magnitude 'star' a few
ring-diameters from Saturn, moving from night to night as it orbits the
planet," notes Adams. Titan is bigger than Mercury and Pluto, and it
has an atmosphere 60% denser than Earth's. In other words, Titan is
a full-fledged world. If it orbited the sun it would surely be considered
a planet.

The curious thing about Titan is how little we know about it. It could
be teeming with life or peppered by ruins from ancient civilizations,
and we wouldn't know because Titan is completely covered by thick
orange clouds. A camera onboard the Hubble Space Telescope has
been able to see through them, to a degree, by observing at infrared
wavelengths. The images hint of continents and seas, but Titan is so
far away even Hubble can't take a clear picture of it.

In January 2005, Cassini will drop the European Space Agency's Huygens probe
through the clouds to find out what lies underneath. This could be one of the
most exciting moments in solar system exploration--ever. Huygens will take more
than 1,100 pictures during its two and a half hour descent by parachute.
Scientific instruments will sample Titan's atmosphere, gauge its winds, and--if
the probe survives landing--measure the physical properties of the
ground.

Huygens probably won't find evidence of life, at least not life as we
know it. Titan is too cold. Its surface temperature, researchers
estimate, is 289°F below zero. This doesn't mean life is impossible,
though. Titan's atmosphere is rich in organic compounds: ethane,
methane, hydrogen cyanide and others. The low temperature of the
moon encourages ethane and methane to liquefy, so there might be
puddles, lakes or even oceans of liquid hydrocarbons sloshing around
on the surface. Perhaps these are places where organic molecules get
together for the first stirrings of simple life.

The truth is, no one knows what Huygens will find. Or Cassini. And
that's what makes exploration fun--something worth pondering this
New Year's Eve. At the stroke of midnight. Looking up at a world of mystery.