Unraveling Saturnian Moon Mysteries
Encircled in purple stratospheric haze, Titan appears as a
softly glowing sphere in this colorized image taken one day after
Cassini's first flyby of that moon.
This image shows two thin haze layers. The outer haze layer is
detached and appears to float high in the atmosphere. Because of
its thinness, the high haze layer is best seen at the moon's
The image was taken using a spectral filter sensitive to
wavelengths of ultraviolet light centered at 338 nanometers. The
image has been falsely colored: The globe of Titan retains the pale
orange hue our eyes usually see, and both the main atmospheric haze
and the thin detached layer have been brightened and given a purple
color to enhance their visibility.
The best possible observations of the detached layer are made in
ultraviolet light because the small haze particles which populate
this part of Titan's upper atmosphere scatter short wavelengths
more efficiently than longer visible or infrared wavelengths.
Images like this one reveal some of the key steps in the
formation and evolution of Titan's haze. The process is thought to
begin in the high atmosphere, at altitudes above 400 kilometers
(250 miles), where ultraviolet light breaks down methane and
nitrogen molecules. The products are believed to react to form more
complex organic molecules containing carbon, hydrogen and nitrogen
that can combine to form the very small particles seen as haze. The
bottom of the detached haze layer is a few hundred kilometers above
the surface and is about 120 kilometers (75 miles) thick.
The image was taken with the narrow angle camera on July 3,
2004, from a distance of about 789,000 kilometers (491,000 miles)
from Titan and at a Sun-Titan-spacecraft, or phase, angle of 114
degrees. The image scale is 4.7 kilometers (2.9 miles) per
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 Cassini-Huygens mission for
NASA's Office of Space Science, Washington (DC). The Cassini
orbiter and its two onboard cameras were designed, developed and
assembled at JPL. The imaging team is based at the Space Science
Institute, Boulder (CO).