Life on Saturn's Moon Titan: Who Needs Water Anyway?

Article excerpt

The search for life on Saturn's moon Titan shows that organisms appear to thrive on far less water than conventional wisdom holds is needed to keep microbes active and alive.

If life gained a foothold on Saturn's moon Titan, what would it be like?

Organisms with a persistent case of malodorous breath? Blood based on liquid methane? Life forms more like lichen than house cats?

That's a picture painted by British astrobiologist William Bains at a Royal Astronomical Society astronomy meeting in Glasgow last week.

But Dirk Schulze-Makuch suggests something simpler, if just as exotic: single-cell Titan residents, similar to the liquid-asphalt- loving species he and his colleagues have discovered in Pitch Lake, a natural pool of liquid asphalt on the island of Trinidad in the Caribbean.

These organisms thrive on liquid hydrocarbons. Lakes filled with liquid methane and other hydrocarbons cover up to 10 percent of Titan's surface at times -- part of what researchers term the moon's hydrocarbon cycle, similar to Earth's water cycle.

Temperatures there are far colder than those found at Pitch Lake, the researchers acknowledge. Still, they say, the discovery marks Pitch Lake as a useful stepping-off point for trying to understand the potential for life in what they call liquid-hydrocarbon environments on Titan.

Scientific sleuthing in tar pits

Compared with bacteria and other single-celled organisms found at natural pitch seeps such as the La Brea Tar Pits in Los Angeles, the organisms at Pitch Lake "were distinctly different from there," says Dr. Schulze-Makuch, an astrobiologist at Washington State University in Pullman, Wash. "About 30 percent of the species we detected are unknown organisms."

But the more profound implication of the discovery may lay in the observation that these organisms appear to thrive on far less water than conventional wisdom holds is needed to keep microbes active and alive, team members say.

In its Mars exploration program, NASA's mantra has been "follow the water." It's a bumper-sticker phrase that highlights the importance scientists have attached to understanding Mar's climate history. That, in turn, will yield important clues on whether the red planet once hosted -- or may still host -- at least simple forms of organic life.

Yet the team's results suggest that it may be as important to follow the liquid, rather than just liquid water.

From an astrobiology standpoint, "that's probably the importance of this," says Villanova University astronomer Edward Guinan, whose research focuses on studying extrasolar planets and the evolution of sun-like stars. Dr. Guinan is a member of the team making the discovery.

Pitch Lake is the world's largest surface reservoir of liquid asphalt. The hydrocarbon lake is some 250 feet deep and covers nearly 100 acres. …


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