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SCIENCE IN THE NEWS DAILY

Tropical Lakes on Saturn Moon Could Expand Options for Life

from Nature News

Nestling among the dunes in the dry equatorial region of Saturn's moon Titan is what appears to be a hydrocarbon lake. The observation, by the Cassini spacecraft, suggests that oases of liquid methane -- which might be a crucible for life -- lie beneath the moon's surface. The work is published today in Nature.

Besides Earth, Titan is the only object in the Solar System to circulate liquids in a cycle of rain and evaporation, although on Titan the process is driven by methane rather than water.

This cycle is expected to form liquid bodies near the moon's poles, but not at its dune-covered equator, where Cassini measurements show that humidity levels are low and little rain falls to the surface. "The equatorial belt is like a desert on Earth, where evaporation trumps precipitation," says astrobiologist Jonathan Lunine of Cornell University in Ithaca, New York.

Any surface liquid there should evaporate and be transported to the cooler poles, where it should condense as rain. "Lakes at the poles are easy to explain, but lakes in the tropics are not," says Caitlin Griffith, a planetary scientist at the University of Arizona in Tucson. Indeed, Cassini has spotted hundreds of lakes and three seas in Titan's polar regions.

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