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Mercury, November/December 1997 Table of Contents

James C. White II
Middle Tennessee State University

Saturn's moon Titan seems like the stuff of science fiction, but it really exists, out there in the distant reaches of our own Solar System. And you can see it.

Having walked a few minutes away from your spacecraft, you stop and peer into the surrounding darkness. Your spacesuit protects you from the elements on this alien world, yet you still feel your body heat drawn out by the aching cold just a few layers of cloth away. No stars are visible as you look skyward, but a faint yellow glow from just above the horizon captures your attention. Ringed Saturn, heavily veiled by the thick atmosphere of this small world, hangs low and huge in the sky.

You drag your gaze down to an even fainter yellow glow coming from the ground in front of you. Stepping forward to investigate, you feel gentle tapping on your boots and quickly look down to make sure no space varmint is wrapping itself around your legs. You're standing in what looks like a puddle of water. Or is it? Shining the flashlight forward, you suddenly realize that you are in fact at the edge of a sea. That faint yellow glow is simply Saturn's reflection in the sea. Waves lapping at your boots, you turn and head back to the ship for equipment, exhilarated to be on the first human expedition to Titan...

Larger than the planet Mercury and about half the size of the Earth, Titan is outsized in the moon category only by Jupiter's larger natural satellite, Ganymede. But the truly incredible chapter in Titan's history is entitled "Thick and Chewy Atmosphere: Blessing or Curse?"

Before the Voyager 1 spacecraft flitted by Saturn and Titan in 1980, astronomers knew of Titan's atmosphere because of the moon's reddish appearance in Earth-bound telescopes. Its air is only slightly thicker than that of our planet and composed, like ours, mostly of nitrogen, with a bit of argon and methane. The similarities between Earth and Titan stop there, though. Titan hangs 10 times as far from the Sun as Earth, which means it is cold and dark -- very cold and very dark.

But under that heavy atmosphere, planetary scientists believe an exotic world awaits our discovery [see "Saturn and Titan on the Eve of Cassini-Huygens," September/October, p. 10]. Lazy ethane waves rolling rhythmically on slushy methane beaches. Cold darkness broken only by the feeble reflected sunlight of Saturn. Snowstorms of organic compounds. Ahhh, to experience the alienness of such a place.

Observing Guidelines

The temptation will be there. Those saturnian rings will beckon you to spend all your time on them, but fight the urge (a little) and socialize with the satellites. Jupiter's Galilean satellites get all the headlines ("Io Hurls Again!" or "A.C. Clarke Was Right! Leave Europa and Its Sub-Ice Ocean Alone!"), yet Saturn's understated ensemble provide just as much entertainment. All you need is a telescope, a sketch pad, pencils, and perhaps a portable cassette player with, say, Lester Young and Hildegard von Bingen tapes.

The great ringed planet floats during November and December amid relatively dim stars on the boundary between Pisces and Cetus. Look to the northeast in early evening to find bright Saturn if you are in the Southern Hemisphere, to the southeast if you are in the northern. In a 4-inch (10-centimeter) telescope, Titan and Iapetus, in their relatively wide orbits, should be visible. Rhea, Dione, and perhaps even Tethys, in their orbits close to Saturn, will probably be visible, too. Even though highly reflective Enceladus has an albedo of nearly 100 percent, you'll need a pretty large telescope to see it.

Your first inclination may be to pop in a 12-mm or 9-mm eyepiece, but fight that urge. The smaller the number on the eyepiece, the greater the magnification -- but the smaller your field of view. Begin with, say, 25 mm. You'll see a small Saturn, yet enough of the sky to spot Titan and even farther-flung Iapetus. To view Rhea, Dione, and possibly Tethys, pop in that 12-mm or 15-mm eyepiece. This will reduce your field of view, but that extra bit of magnification may bring these inner moons out. And if you want to see detail in those exquisite rings, drop in the smallest-numbered eyepiece.

For each of your observations, sketch Saturn, showing the correct ring tilt (always work on these observing skills); identify what you believe are moons; and draw them with respect to Saturn. Sky & Telescope magazine has a panel on the orbital locations of Saturn's satellites. This or a software package such as Carina's Voyager II is invaluable as you sort out the moons' motions.

Your Guest Observer report should include notes, general sketches or photographs, and one summary sketch of the moon's locations, relative to Saturn, over several nights. Note observation times and, using your moon info, put names to the dots. The orbits should be apparent after 10 or so observations.

Please submit your completed report by Jan. 31, 1998, by regular mail to Jay White, Attn: Guest Observers, Department of Physics and Astronomy, Middle Tennessee State University, Murfreesboro, Tenn., 37132. We welcome reports from observers of all ages in all countries. The selection committee will evaluate the reports and choose the Guest Observer for a future issue.

JAMES C. WHITE II is an astronomy professor at Middle Tennessee State University in Murfreesboro. His email address is jwhite@physics.mtsu.edu.