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This artist's illustration shows the likely slushy interior structure of Saturn's moon Titan deduced from gravity field data collected by NASA's Cassini spacecraft. Full Story. Credit: NASA/JPL |
The insides of Saturn?s largest moon Titan
are arranged like a slushy mix of rock and ice instead of the rigidly layered
structures found in other bodies across the solar system, NASA's Cassini
spacecraft has found.
Astronomers were able to determine the
temperature and consistency of Titan's slushy innards by measuring the
gravitational tugs registered by Cassini as it flew by the cloudy Saturn
moon.
"There have been several flybys of Titan
by Cassini," said study co-author David Stevenson, a professor of
planetary science at the California Institute of Technology in Pasadena, Calif.
"As it goes by, its path is deflected by the
gravity of Titan. We use that deflection to learn about the gravity of
Titan."
The gravity data reveals that the first 300
miles (500 km) down into Titan
is devoid of any rock fragments, while ice and rock are mixed to various
extents at greater depths. Cassini was able to record the data during four
flybys of Titan between February 2006 and July 2008.
Scientists have long-known that Titan is made
up of about equal parts rock and ice. Cassini's gravity data confirmed
that finding and also revealed new details on the exact consistency and
distribution of the interior material's makeup.
Cassini researchers described Titan's
interior as "a sorbet of ice studded with rocks," in a recent NASA
statement.
Researchers think Titan never heated
up beyond a relatively lukewarm temperature, which explains why the moon's ice
and rock have not fully divided and formed layers within Titan's interior like
other bodies in the solar system.
"To avoid separating the ice and the
rock, you must avoid heating the ice too much," Stevenson told SPACE.com.
"This means that Titan was built rather slowly for a moon, in perhaps
around a million years or so, back soon after the formation of the solar
system."
Cassini built the gravity map of Titan by
flying about 800 to 1,200 miles (1,300 to 1,900 km) above the moon. Scientists
then used ground-based antennas with the Deep Space Network to note changes
within five thousandths of a millimeter per second in the Cassini's speed as
Titan's gravity perturbed the spacecraft path along its orbit.
"These results are fundamental to understanding
the history of moons of the outer solar system," said Cassini project scientist
Bob Pappalardo at JPL. "We can now better
understand Titan's place among the range of icy satellites in our solar
system."
Cassini
has been studying Saturn and its rings and moons since 2004, when it arrived in
orbit around the gas giant planet. The spacecraft completed its initial mission
in 2008 and received and extended flight through 2017 earlier this year.
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