|10-26-2004, 09:31 PM||#1|
Join Date: Oct 2001
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A tour of Titan
A Tour of Titan
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
20 October 2000
You wake long after dawn on Titan, Saturn's largest moon. There's no rush: The day will be long -- 15.9 Earth days, to be exact.
Outside, the sky is dim, not unlike a terrestrial night under a full Moon. But orange.
You slip into the most advanced spacesuit known to humans. Protection against the deep freeze. You know that summer or winter, north or south, the intense cold is ubiquitous. Voyager spacecraft data proved that long ago.
Outside, boots kick up dust and crunch firm ice below. A great river of methane flows past your living quarters into a tranquil sea -- liquid but foreign, it stretches beyond the horizon.
Behind you the largest of Titan's mountains rises somewhat pitifully into the hazy sky. Titanic mountains these are not -- none reach more than 6,500 feet (2,000 meters) high. A hill, by Colorado standards.
Above, the Sun is a fuzzy orange tennis ball, almost inconsequential because of the great distance, rendered even less effective by the persistent layer of smog. A haze-obscured Saturn looms like a giant ghost, close enough to touch.
Gentle breezes loft a scant few puffy clouds high into the sky -- nearly twice as high as any you recall from back home.
And it looks like rain.
The Titan we know, and the Titan we don't
"It is cold, dark and quiescent," explains Caitlin Griffith, Northern Arizona University researcher whose new study has found strong evidence for clouds and rain on Titan.
Griffith and others say little is known about the shrouded moon's surface. This much is speculated: the presence of methane oceans and rivers; a layer of surface dust caused by settling smog; bedrock composed of water ice; and as with the moons of Jupiter, Titan's mountains are probably modest in height.
But thanks to Griffith and her colleagues, Joseph Hall and Thomas Geballe, a picture of Titan's atmosphere is becoming clearer.
"We would not be able to see outside the atmosphere well enough to make out stars through the smog's veil," Griffith explains. "On the ground, the atmosphere would be clear and the visibility un-obscured.
"Every week, sparse clouds might appear high in the sky, barely visible. They would quickly produce rain and disappear. Very infrequently, perhaps once a year, clouds would blanket the sky for a day or two."
The annual profusion of clouds, like many things about Titan, is inexplicable.
While no one is recommending human travel to Titan anytime soon, Griffith and her colleagues hope the Cassini space probe, due to arrive in 2004, will serve well as a scientific stand-in, furthering our knowledge of the odd moon.
More Titan facts
* Titan's diameter is 3,200 miles (5,150 kilometers), about 40 percent as large as Earth.
* The thick haze is about 120 miles (200 kilometers) up.
* The atmospheric pressure near Titan's surface is 60 percent greater than on Earth at sea level.
* The atmospheric temperature near Titan's surface is minus 288 degrees Fahrenheit (minus 178 degrees Celsius).
* As on Earth, the most abundant gas in Titan's atmosphere is nitrogen. Unlike our home planet, methane is the second most abundant gas. More than a dozen other gases are also present.
* The thickness (extent) of Titan's atmosphere is about 10 times that of Earth.
* Titan is the second largest moon in the solar system; only Jupiter's Ganymede is larger.
* Titan and Ganymede are both larger than the planets Mercury and Pluto.
* Titan apparently keeps the same face toward Saturn as it orbits the gas-giant planet (our Moon also keeps one face toward Earth at all times). Hence a Titanic "day" is equivalent to the time it takes it to orbit Saturn.
* Titan orbits Saturn in just under 16 Earth days (orbital period = 15.9454 days).
* Titan orbits Saturn at a distance of 759,210 miles (1,221,830 kilometers) from Saturn's center.