Organic Materials Spotted High Above Titan's Surface
During its closest flyby of Saturn's moon Titan on April 16, the
Cassini spacecraft came within 1,027 kilometers (638 miles) of
the moon's surface and found that the outer layer of the thick,
hazy atmosphere is brimming with complex hydrocarbons.
Image above: Three views of Titan, from left to right, natural color, near-infrared and false color. Image credit: NASA/JPL/Space Science Institute.
+ Full image and caption.
Scientists believe that Titan's atmosphere may be a laboratory
for studying the organic chemistry that preceded life and
provided the building blocks for life on Earth. The role of the
upper atmosphere in this organic "factory" of hydrocarbons is
very intriguing to scientists, especially given the large number
of different hydrocarbons detected by Cassini during the flyby.
Cassini's ion and neutral mass spectrometer detects charged and
neutral particles in the atmosphere. It provides scientists with
valuable information from which to infer the structure, dynamics
and history of Titan's atmosphere. Complex mixtures of
hydrocarbons and carbon-nitrogen compounds were seen throughout
the range of masses measured by the Cassini ion and neutral mass
"We are beginning to appreciate the role of the upper atmosphere
in the complex carbon cycle that occurs on Titan," said Dr.
Hunter Waite, principal investigator of the Cassini ion and
neutral mass spectrometer and professor at the University of
Michigan, Ann Arbor. "Ultimately, this information from the
Saturn system will help us determine the origins of organic
matter within the entire solar system."
Hydrocarbons containing as many as seven carbon atoms were
observed, as well as nitrogen-containing hydrocarbons (nitriles).
Titan's atmosphere is composed primarily of nitrogen, followed by
methane, the simplest hydrocarbon. The nitrogen and methane are
expected to form complex hydrocarbons in a process induced by
sunlight or energetic particles from Saturn's magnetosphere.
However, it is surprising to find the plethora of complex
hydrocarbon molecules in the upper reaches of the atmosphere.
Titan is very cold, and complex hydrocarbons would be expected to
condense and rain down to the surface.
"Biology on Earth is the primary source of organic production we
are familiar with, but the key question is: what is the ultimate
source of the organics in the solar system?" added Waite.
Interstellar clouds produce abundant quantities of organics,
which are best viewed as the dust and grains incorporated in
comets. This material may have been the source of early organic
compounds on Earth from which life formed. Atmospheres of planets
and their satellites in the outer solar system, while containing
methane and molecular nitrogen, are largely devoid of oxygen. In
this non-oxidizing environment under the action of ultraviolet
light from the Sun or energetic particle radiation (from Saturn's
magnetosphere in this case), these atmospheres can also produce
large quantities of organics, and Titan is the prime example in
our solar system. This same process is a possible pathway for
formation of complex hydrocarbons on early Earth.
This was Cassini's sixth flyby of Titan, but its exploration has
just begun. Thirty-nine more flybys of this strange, remote world
are planned during Cassini's nominal mission. The next Titan
flyby is August 22.
The latest images from the Titan flyby are available at:
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 mission for NASA's Science Mission
Directorate, Washington, D.C.
Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.