Images from Titan indicate liquid, ice

Scientists view radar data captured by spacecraft passing moon of Saturn

October 29, 2004|By John Johnson | John Johnson,LOS ANGELES TIMES

PASADENA, Calif. - The first radar images of Saturn's smoggy moon Titan show what appears to be a large lake, rolling ridges and lava-like flows of ice or ammonia, researchers at the Jet Propulsion Laboratory here said yesterday.

The images from the Cassini spacecraft provide the best evidence yet that liquid lakes, or even seas, exist on Titan's surface, team members said.

The potential lake was christened "Si-Si the Halloween Cat" in honor of a scientist's daughter who first recognized the feline resemblance in its shape.

The putative lake appeared as a blackened-out area about the size of Lake Tahoe on the radar image.

The Cassini team urged caution in interpreting the findings because the black-and-white radar image covered only 1 percent of the moon's surface, a swath of land roughly 75 miles wide and 1,250 miles long.

Over the next four years, Cassini is scheduled to make 44 more close passes of Titan, which scientists said should provide a much clearer picture of the solar system's second-largest moon.

Organic material

On the basis of data received from the first close pass Tuesday, some space scientists said the frozen moon could turn out to be the strangest place in the solar system.

Not only does it likely possess methane lakes and water ice, but the surface appears to be heavily carpeted in organic material, such as ethane, propane and acetylene. Those compounds had already been observed high in the moon's atmosphere.

Researchers speculate that the surface might be the consistency of powder, flakes or even sticky, plastic-like substances.

"Titan is an extremely dynamic and active place," said Jonathan Lunine, a Cassini scientist from the University of Arizona.

Although it is too cold for life, with temperatures as low as minus 290 degrees Fahrenheit, Titan appears to be a massive organic chemistry laboratory in which carbon-based substances could be endlessly combining and recombining into a wide variety of molecules.

"Titan is really covered in organics," said Ralph Lorenz, a member of the radar imaging team.

Cassini's radar also produced streaky images that scientists said could be ice ridges. Other images resembled lava-like flows. They couldn't be from an erupting volcano, however, because Titan's interior isn't hot enough to melt rock.

Flat, lacking craters

The landscape surveyed in the close approach was definitely flat, scientists said, with variations in elevation of little more than 150 feet.

No craters were detected, though such a large moon would have been struck by asteroids many times in its history.

Although its atmosphere is much denser than Earth's, Titan is far less massive, being composed of equal proportions of water ice and rock. The flows on Titan are probably liquid water and possibly ammonia, Lunine said.

Lunine speculated that the ridges were the result of the very thin surface cracking open under pressure.

Scientists hope to learn more when Cassini sends its Huygens probe to the surface in January.

If it survives the landing, Huygens is designed to analyze the atmosphere, as well as the surface, possibly answering questions as to whether Titan has a gloppy, sticky, powdery or rocky surface. Or all of the above.

The $3.2 billion mission is a collaboration among the National Aeronautics and Space Administration, the European Space Agency and the Italian Space Agency.

The Los Angeles Times is a Tribune Publishing newspaper. The New York Times contributed to this article.

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