[meteorite-list] Scientists Discover Possible Titan Volcano

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Jun 8 16:22:04 2005
Message-ID: <200506082021.j58KLN021869_at_zagami.jpl.nasa.gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

News Release: 2005-096 June 8, 2005

Scientists Discover Possible Titan Volcano

A recent flyby of Saturn's hazy moon Titan by the Cassini
spacecraft has revealed evidence of a possible volcano,
which could be a source of methane in Titan's atmosphere.

Images taken in infrared light show a circular feature
roughly 30 kilometers (19 miles) in diameter that does not
resemble any features seen on Saturn's other icy moons.
Scientists interpret the feature as an "ice volcano," a
dome formed by upwelling icy plumes that release methane
into Titan's atmosphere. The findings appear in the June
9 issue of Nature.

"Before Cassini-Huygens, the most widely accepted explanation
for the presence of methane in Titan's atmosphere was the
presence of a methane-rich hydrocarbon ocean," said Dr.
Christophe Sotin, distinguished visiting scientist at NASA's
Jet Propulsion Laboratory, Pasadena, Calif.

"The suite of instruments onboard Cassini and the observations
at the Huygens landing site reveal that a global ocean is not
present," said Sotin, a team member of the Cassini visual and
infrared mapping spectrometer instrument and professor at the
University de Nantes, France.

"Interpreting this feature as a cryovolcano provides an
alternative explanation for the presence of methane in Titan's
atmosphere. Such an interpretation is supported by models of
Titan's evolution," Sotin said.

Titan, Saturn's largest moon, is the only known moon to have a
significant atmosphere, composed primarily of nitrogen, with 2
to 3 percent methane. One goal of the Cassini mission is to
find an explanation for what is replenishing and maintaining
this atmosphere. This dense atmosphere makes the surface very
difficult to study with visible-light cameras, but infrared
instruments like the visual and infrared mapping spectrometer
can peer through the haze. Infrared images provide information
about both the composition and the shape of the area studied.

The highest resolution image obtained by the visual and
infrared mapping spectrometer instrument covers an area 150
kilometers square (90 miles) that includes a bright circular
feature about 30 kilometers (19 miles) in diameter, with two
elongated wings extending westward. This structure resembles
volcanoes on Earth and Venus, with overlapping layers of
material from a series of flows.
  
"We all thought volcanoes had to exist on Titan, and now we've
found the most convincing evidence to date. This is exactly
what we've been looking for," said Dr. Bonnie Buratti, team
member of the Cassini visual and infrared mapping spectrometer
at JPL.

In the center of the area, scientists clearly see a dark
feature that resembles a caldera, a bowl-shaped structure formed
above chambers of molten material. The material erupting from
the volcano might be a methane-water ice mixture combined with
other ices and hydrocarbons. Energy from an internal heat source
may cause these materials to upwell and vaporize as they reach
the surface. Future Titan flybys will help determine whether
tidal forces can generate enough heat to drive the volcano, or
whether some other energy source must be present. Black channels
seen by the European Space Agency's Huygens probe, which
piggybacked on Cassini and landed on Titan's surface in January
2005, could have been formed by erosion from liquid methane rains
following the eruptions.

Scientists have considered other explanations. They say the
feature cannot be a cloud because it does not appear to move and
it is the wrong composition. Another alternative is that an
accumulation of solid particles was transported by gas or liquid,
similar to sand dunes on Earth. But the shape and wind patterns
don't match those normally seen in sand dunes.

The data for these findings are from Cassini's first targeted
flyby of Titan on Oct. 26, 2004, at a distance of 1,200 kilometers
(750 miles) from the moon's surface.

The visual and infrared mapping spectrometer instrument can detect
352 wavelengths of light from 0.35 to 5.1 micrometers. It
measures the intensities of individual wavelengths and uses the
data to infer the composition and other properties of the
object that emitted the light; each chemical has a unique
spectral signature that can be identified.

Forty-five flybys of Titan are planned during Cassini's four-year
prime mission. The next one is Aug. 22, 2005. Radar data of the
same sites observed by the visual and infrared mapping spectrometer
may provide additional information.

For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini . The
visual and infrared mapping spectrometer page is at
http://wwwvims.lpl.arizona.edu .

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet
Propulsion Laboratory, a division of the California Institute of
Technology in Pasadena, manages the mission for NASA's Science
Mission Directorate, Washington, D.C. The Cassini orbiter was
designed, developed and assembled at JPL. The visual and infrared
mapping spectrometer team is based at the University of Arizona.

-end-
Received on Wed 08 Jun 2005 04:21:23 PM PDT