archiv~1.txt: SETI [ASTRO] Saturn's Mysterious Moon

SETI [ASTRO] Saturn's Mysterious Moon

Larry Klaes ( )
Thu, 11 Mar 1999 08:12:46 -0500

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>Date: Wed, 10 Mar 1999 22:42:51 GMT
>From: Ron Baalke <>
>Subject: [ASTRO] Saturn's Mysterious Moon
>Reply-To: Ron Baalke <>
>Saturn's Mysterious Moon
>Marshall Space Flight Center
>Skywatchers can view Saturn's enigmatic moon Titan through a small telescope
>this week
>Mar. 10, 1999: Since mid-February the western sky has been a showcase of
>bright planets. On Feb. 23, Venus and Jupiter executed a dazzling
>conjunction seen by millions. Barely two weeks later Mercury appeared from
>behind the sun and four planets -- Mercury, Venus, Jupiter, and Saturn --
>were visible at the same time in the western sky.
>The show is continuing this week, and this time the star, or rather the
>planet, is Saturn.
>Saturn is visible to the naked eye soon after sunset. To find the ringed
>planet, it's easiest to "planet-hop" from Venus. Face west-southwest after
>the sun sets and look just above the horizon. Venus, at magnitude -4.0, will
>be impossible to miss. Venus is so bright that it is often mistaken for an
>airplane, but it does not blink or move so it should be easy to identify.
>Saturn is to the upper left of Venus, approximately 10 degrees away. At
>magnitude +0.5, it will be easily visible to the naked eye.
>Saturn is widely regarded as the jewel of the night sky. It's not the
>brightest planet as seen from Earth, but it rarely fails to evoke a gasp of
>awe when seen through a telescope for the first time. The reason, of course,
>is Saturn's spectacular system of rings spanning over a half a million
>kilometers in diameter.
>This week Saturn offers an added bonus to sky watchers with access to a
>small telescope. From Wednesday, March, 10 through Friday March 12, Saturn's
>largest moon Titan will be visible about 4 ring-lengths west of the planet.
>Titan is one of the strangest places in the Solar System. It is larger than
>the planets Mercury and Pluto, and is one of only two moons known to have a
>substantial atmosphere (Neptune's moon Triton is the other). Although Titan
>has been photographed by spacecraft and Earth's most powerful telescopes,
>its cloud-covered surface remains a mystery. Titan's thick atmosphere is
>mostly nitrogen, like Earth's, but contains much higher percentages of
>chemicals such as methane and ethane. The "smog" may be so thick that it
>actually rains "gasoline-like" liquids.
>While Titan's surface is normally hidden from view, astronomers have
>succeeded in peering through the haze by observing Titan at near-infrared
>wavelengths with the Hubble Space Telescope. At infrared wavelengths, which
>are longer than visible light, Titan's smog-like atmosphere begins to be
>transparent enough to allow glimpses of its surface. The bright feature seen
>in the Hubble image below is about 2,500 miles across, similar in size to
>Australia. The bright and dark areas might represent oceans, continents,
>craters, or other features. There is much speculation, but no one knows.
>Many basic questions about Titan may be answered by the Cassini mission,
>which was launched in 1997 for a rendevous with Saturn in 2004. Once in the
>Saturn system, the spacecraft will release the European Space Agency's
>Huygens Probe. The probe will drop into Titan's atmosphere and slowly
>descend to the surface by parachute. Onboard instruments will measure
>temperature, pressure, density and energy balance in the atmosphere
>throughout the descent. As the Huygens probe breaks through the cloud deck,
>a camera will capture pictures of the Titan panorama. Other instruments will
>directly measure the organic chemistry in Titan's atmosphere, which is
>thought to resemble that of early Earth. Instruments will also be used to
>study properties of Titan's surface remotely, and perhaps even directly if
>the probe survives the descent and landing.
>Astronomers will undoubtedly continue their studies of Titan from afar, but
>Titan is likely to remain an enigma until Cassini reaches Saturn in 2004.
>For now, star gazers who see a tiny point of light west of Saturn's rings
>this week must rely on their own imaginations to provide the answers to the
>mysteries of Saturn's wondrous moon.