for National Geographic News
Saturn's moon Titan has odd clouds forming downwind of its lakes—apparently much like clouds seen near North America's Great Lakes, scientists said Monday.
The clouds appear to form from liquid evaporating from the lakes, which then recondense over land, said Mike Brown, a planetary astronomer at the California Institute of Technology.
Near the Great Lakes, similar ribbons of clouds called lake effect clouds form downwind on cold winter days, according to data from NASA's Cassini orbiter.
"Titan is like Buffalo, [New York], without the Bills," Brown quipped.
(Related: "Huge Space Lake Confirmed on Saturn's Moon Titan" [July 31, 2008].)
Scientists have long been interested in a cloud cap above Titan's north pole.
The cloud cap's main layer sits about 40 to 50 kilometers (about 25 to 30 miles) above the moon's surface.
But recent measurements have found another cloud layer—apparently made of the chemical compound methane—about about 6 to 12 miles (10 to 20 kilometers) below that.
"If you look closely at [these] clouds, you see knots and streaks in them," Brown said at an American Geophysical Union meeting in San Francisco.
"They change very rapidly."
In addition to observing lake effect cloud shapes on Titan, Brown noticed that the supposed lake effect clouds only occur downwind of a high-latitude region known to have large lakes.
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