Image: Titan map
ESO
The European Southern Observatory's map of Titan's surface highlights four fanciful forms. From left, they are the Lying H, the Ball, the Dog and the Dragon's Head. The dark features may be hydrocarbon oceans.
By Senior Science Writer
updated 4/20/2004 5:42:06 PM ET 2004-04-20T21:42:06

The most detailed images ever made of Saturn's moon Titan reveal surface features in unprecedented clarity. What emerges — in addition to some useful science — are a dog and a dragon imagined by playful European scientists.

The animals on Titan are actually light and dark regions that indicate areas of high and low reflectivity, suggesting differing compositions on the mostly mysterious moon. The results support other tantalizing hints that the huge moon is at least partly covered by giant seas of liquid hydrocarbons such as methane and ethane.

In separate new observations by the Keck Telescope in Hawaii, astronomers have peered into Titan's smoggy atmosphere and produced an animated plunge through it.

Both studies may help mission managers make final plans for observations by the Cassini spacecraft and its piggybacked Huygens probe, which will parachute to the surface of Titan early next year.

Cassini-Huygens will go into orbit around Saturn in July after a nearly seven-year journey. The mothership will explore Saturn's atmosphere, rings and moons, including Titan on several flybys. Huygens is expected to provide a remarkable and potentially breakthrough look at the unexplored surface of Titan and, scientists hope, reveal in pictures and other data how much Titan resembles the planet Earth in its early years.

Big and smoggy
At 3,200 miles (5,150 kilometers) wide, Titan is Saturn's largest moon. It is the second-largest moon in the solar system behind Jupiter's Ganymede. Titan is about 40 percent the diameter of Earth and roughly 50 percent larger than Earth's moon.

Titan is the only moon with a substantial atmosphere, made mostly of nitrogen, just as is Earth's air.

The air of Titan is also laden with methane, contributing to a smoggy haze of organic molecules that until recent years has prevented any observations of the surface. The methane is continually altered by sunlight, creating hydrocarbons that condense into particulate matter — or smog.

Radar and other observations have indicated the presence of seas and suggested the moon may experience methane rains in a cycle of hydrological activity resembling that on Earth.

Too cold for earthly life
Though too cold to support life as we know it — minus-290 degrees Fahrenheit (-179 Celsius) — the moon is expected to contain interesting prebiotic chemistry. Scientists have long sought to explore the mix in an effort to get an inkling of what Earth might have been like just before life arose from a possibly similar soup of organic chemicals.

Another recent study predicts that Titan's seas, assuming they exist, should contain huge waves, owing to the lesser gravity compared to Earth. Hydrocarbons can remain liquid at much lower temperatures than water.

It is not known what sort of surface the probe will encounter, however. Scientists have said bright glints seen on Titan are consistent with reflections of a hydrocarbon sea. But they can't rule out smooth land features. The first known bright area, seen by the Hubble Space Telescope back in 1994, was about the size of Australia.

Given this limited knowledge and the impending arrival of the Huygens probe, astronomers around the world are mounting multiple ground-based efforts to stretch telescoping to its limits and provide as much information as possible over the next few months.

Best looks yet
The fresh images of Titan's surface were made with a new Simultaneous Differential Imager on the Very Large Telescope at the European Southern Observatory in Chile.

"I'm far too cautious a scientist say these images say absolutely that Titan has hydrocarbon oceans," said Laird Close, who built the camera. "But this does agree with the general gist of the scientific community."

The camera was not designed with Titan as its prime sort of target.

"This camera was invented to look for planets around other stars," Close, of the University of Arizona, told Space.com. "But it turns out that it enables you to take pictures of the atmosphere of a moon, too."

Close and his colleagues have passed their maps and other data on to researchers working on the Huygens mission. "It can't hurt to have a good map of Titan," he said.

Slices of atmosphere
The Keck Telescope observations also peer through the hydrocarbon haze, but instead of seeing Titan's surface, they were designed to split the atmosphere into several slices. The snapshots were combined into a movie that shows how the atmosphere changes from top to bottom -- exactly what Huygens will see on the way down.

"Before, we could see each component of the haze but didn't know where exactly it was in the stratosphere or the troposphere," said atmospheric chemist Mate Adamkovics, a graduate student at the University of California at Berkeley. "These are the first detailed pictures of the distribution of haze with altitude."

The observations confirm previous findings and refine knowledge of how the haze is distributed.

Haze over Titan's south pole is evident between 19 and 31 miles (30 to 50 kilometers) altitude and dissipates seasonally in Titan's long year, which lasts about 29.5 Earth years. Across a broad part of the northern hemisphere, haze is visible high in the stratosphere of Titan, about 93 miles (150 kilometers) up. The stratospheric haze is absent from the southern hemisphere.

The movie is available at http://astron.berkeley.edu/~madamkov/titan/.

Space.com's Tariq Malik contributed to this report.

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