Saturn's smoggy moon Titan has hundreds of times more natural gas and other liquid hydrocarbons than all the known oil and natural gas reserves on Earth, scientists said today.

The hydrocarbons rain from the sky on the miserable moon, collecting in vast deposits that form lakes and dunes. This much was known. But now the stuff has been quantified using observations from NASA's Cassini spacecraft.

"Titan is just covered in carbon-bearing material — it's a giant factory of organic chemicals," said Ralph Lorenz, a Cassini radar team member from the Johns Hopkins University Applied Physics Laboratory. "This vast carbon inventory is an important window into the geology and climate history of Titan."

At minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan would be an awful place to live. Instead of water, liquid hydrocarbons in the form of methane and ethane are present on the moon's surface, and tholins probably make up its dunes. The term "tholins" was coined by Carl Sagan in 1979 to describe the complex organic molecules at the heart of prebiotic chemistry.

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Titan has long been viewed as a place that might be somewhat like Earth just before biology got going.

Cassini has mapped about 20 percent of Titan's surface with radar. Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves, according to a NASA statement. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.

Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300 times the amount of energy the entire United States uses annually for residential heating, cooling and lighting, according to the release. Dozens of Titan's lakes individually have the equivalent of at least this much energy in the form of methane and ethane.

"This global estimate is based mostly on views of the lakes in the northern polar regions," Lorenz said. "We have assumed the south might be similar, but we really don't yet know how much liquid is there."

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