Surprise Hidden in Titan's Smog: Cirrus-Like Clouds

Feature: 2011-040 Feb. 3, 2011

Surprise Hidden in Titan's Smog: Cirrus-Like Clouds

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-040&cid=release_2011-040

Every day is a bad-air day on Saturn's largest moon, Titan. Blanketed by haze far worse than any
smog belched out in Los Angeles, Beijing or even Sherlock Holmes' London, the moon looks like
a dirty orange ball. Described once as crude oil without the sulfur, the haze is made of tiny
droplets of hydrocarbons with other, more noxious chemicals mixed in. Gunk.

Icky as it may sound, Titan is really the rarest of gems: the only moon in our solar system with an
atmosphere worthy of a planet. This atmosphere comes complete with lightning, drizzle and
occasionally a big, summer-downpour style of cloud made of methane or ethane—hydrocarbons
that are best known for their role in natural gas.

Now, thin, wispy clouds of ice particles, similar to Earth's cirrus clouds, are being reported by
Carrie Anderson and Robert Samuelson at NASA's Goddard Space Flight Center in Greenbelt,
Md. The findings, published this week in the journal Icarus, were made using the composite
infrared spectrometer on NASA's Cassini spacecraft.

Unlike Titan's brownish haze, the ice clouds have the pearly white appearance of freshly fallen
snow. Their existence is the latest clue to the workings of Titan's intriguing atmosphere and its
one-way "cycle" that delivers hydrocarbons and other organic compounds to the ground as
precipitation. Those compounds don't evaporate to replenish the atmosphere, but somehow the
supply has not run out yet.

"This is the first time we have been able to get details about these clouds," says Samuelson, an
emeritus scientist at Goddard and the co-author of the paper. "Previously, we had a lot of
information about the gases in Titan's atmosphere but not much about the [high-altitude]
clouds."

Compared to the puffy methane and ethane clouds found before in a lower part of the
atmosphere by both ground-based observers and in images taken by Cassini's imaging science
subsystem and visual and infrared mapping spectrometer, these clouds are much thinner and
located higher in the atmosphere. "They are very tenuous and very easy to miss," says Anderson,
the paper's lead author. "The only earlier hints that they existed were faint glimpses that NASA's
Voyager 1 spacecraft caught as it flew by Titan in 1980."

The full story is online at:
http://www.nasa.gov/mission_pages/cassini/whycassini/titan-clouds.html .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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 and its two onboard cameras were
designed, developed and assembled at JPL. The CIRS team is based at NASA's Goddard Space
Flight Center in Greenbelt, Md., where the instrument was built.

#2011-040

Written by Elizabeth Zubritsky/NASA Goddard Space Flight Center, Greenbelt, Md.

Media contact: Jia-Rui Cook/Priscilla Vega
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850/354-1357
jccook@jpl.nasa.gov / Priscilla.r.vega@jpl.nasa.gov

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