Cassini Radar Images Show Dramatic Shoreline on Titan
Images returned during Cassini's recent flyby of Titan show captivating
evidence of what appears to be a large shoreline cutting across the smoggy
moon's southern hemisphere. Hints that this area was once wet, or
currently has liquid present, are evident.
Image right: Radar image of Titan showing that the boundary of the bright (rough) region and the dark (smooth) region appears to be a shoreline. Image credit: NASA/JPL
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"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,
The new radar images can be seen at: http://www.nasa.gov/cassini
The images show what looks like a shoreline dividing a distinct bright and
dark region roughly 1,700 kilometers long by 170 kilometers wide (1,060 by
106 miles). Directly to the right of a bright and possibly rough area is
one that is very dark and smooth.
"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."
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.
"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
Dr. Ellen Stofan, Cassini associate radar team member from Proxemy Research,
Taken together with the two other radar passes in October 2004 and February
2005, these very high resolution images have identified at least two distinct
types of drainage and channel formation on Titan. Some channels in images
from this pass are long and deep, with angular patterns and few tributaries,
suggesting that fluids flow over great distances. By contrast, others show
channels that form a denser network that might indicate rainfall.
Dr. 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."
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.
Cassini encountered an anomaly with one of two solid-state recorders during the Sept. 7
close flyby, resulting in some data not being recorded. Half of the data from the flyby
was received, much to the delight of anxious scientists. The spacecraft team is
troubleshooting the cause, and early indications point to a software problem that would
be correctable with no long-term impacts.
This was Cassini's eighth out of 45 Titan flybys planned in the nominal four-year tour.
The next radar pass will be Oct. 26 when the team will focus on the Huygens probe
landing site close to the equator.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space
Agency and the Italian Space Agency. JPL, a division of the California Institute
of Technology in Pasadena, manages the Cassini-Huygens mission for NASA?s Science
Mission Directorate, Washington. The Cassini orbiter was designed, developed and
assembled at JPL. The radar instrument team is based at JPL, working with team
members from the United States and several European countries.
Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.