You might have
thought Saturn's moon Titan was a somewhat dead issue after the Cassini
spacecraft did not find convincing evidence for methane seas that scientists
had predicted
would exist.
But the smoggy moon
is back in the news today as a new Cassini image reveals a dark
feature that scientists speculate might be a lake.
The feature is
"remarkably lake-like," according to a NASA statement that noted the
appearance of smooth, shore-like boundaries unlike any seen previously on
Titan.
"I'd say
this is definitely the best candidate we've seen so far for a liquid
hydrocarbon lake on Titan," said Alfred McEwen, imaging team member and a
professor at the University of Arizona.
The feature is
145 miles long by 45 miles wide (230 by 70 kilometers), or about the size of
Lake Ontario on the U.S. Canadian border.
The possible
lake is under the densest clouds on Titan. Scientists speculate methane rains
might have fallen there recently.
"It's
possible that some of the storms in this region are strong enough to make
methane rain that reaches the surface," Cassini
imaging team member Tony DelGenio of NASA's Goddard
Institute for Space Studies in New York. "Given Titan's cold temperatures,
it might take a long time for any liquid methane collecting on the surface to
evaporate. So it might not be surprising for a methane-filled lake to persist
for a long time."
It's also
possible the feature was once a lake, but has since dried up, leaving behind
dark deposits, said Elizabeth Turtle, Cassini imaging team associate
at the University of Arizona. Or the region is simply a broad depression filled
by dark, solid hydrocarbons falling from the atmosphere onto Titan's surface.
In this case, the smooth outline might be the result of a process unrelated to
rainfall, such as a sinkhole or a volcanic caldera.
A previous
image of Titan revealed what scientist believe to be a
volcano.
"It is
already clear that whatever this lake-like feature turns out to be, it is only
one of many puzzles that Titan will throw at us as we continue our
reconnaissance of the surface over the next few years," said Carolyn Porco, imaging team leader at the Space
Science Institute in Boulder, Colo.
Officials plan
39 more Titan flybys.
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