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On icy shores far, far away

Digital images transmitted to Earth from the unmanned Cassini spacecraft's recent flyby of Saturn's big moon Titan show clear evidence of a coastline located in the moon's southern hemisphere.

According to NASA's Carolina Martinez, "Hints that this area was once wet, or currently has liquid present, are evident." Unlike Earth, however, Titan's shorelines are lapped by an ultra-cold liquid hydrocarbon sea, perhaps liquid ethane.

"We've been looking for evidence of oceans or seas on Titan for some time. This radar data is among the most telling evidence so far for a shoreline," said Steve Wall, radar deputy team leader from NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The amazing pictures provide a look down on a shoreline dividing two regions roughly 1,060 by 106 miles, said Martinez. "This is the area where liquid or a wet surface has most likely been present, now or in the recent past, said Wall. "Titan probably has episodic periods of rainfall or massive seepages of liquid from the ground."

"We also see a network of channels that run across the bright terrain, indicating that fluids, probably liquid hydrocarbons, have flowed across this region," said Ellen Stofan, Cassini radar expert.

The brightness patterns in the dark area indicate that it may once have been flooded with liquid that may now have partially receded. Bay-like features also lead scientists to speculate that the bright-dark boundary is most likely a shoreline, Martinez said.

Larry Soderblom with the U.S. Geological Survey in Flagstaff, Ariz., said, "It looks as though fluid flowed in these channels, cutting deeply into the icy crust of Titan. Some of the channels extend over 100 kilometers (60 miles). Some of them may have been fed by springs, while others are more complicated networks that were likely filled by rainfall."

According to a NASA news release, Titan has an environment somewhat similar to that of Earth before biological activity forever altered the composition of Earth's atmosphere. The major difference on Titan, however, is the absence of liquid water, and Titan's very low temperature. With a thick, nitrogen-rich atmosphere, Titan was until recently presumed to hold large seas or oceans of liquid methane. Cassini has been in orbit around Saturn for a year and has found no evidence for these large seas.

What's in the Sky: Ironically, the month of September , which means seventh month, is actually the nine calendar month. What gives? The early Roman calendar began in March and lasted just 10 months. January and February were later creations. It was Julius Caesar who decided that the new year would begin with January.

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