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
Organisms with a persistent case of malodorous breath? Blood
based on liquid methane? Life forms more like lichen than house
That's a picture painted by British astrobiologist William Bains
at a Royal Astronomical Society astronomy meeting in Glasgow last
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
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
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
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. …