A montage of Cassini images, taken in four different regions of the
spectrum from ultraviolet to near-infrared, demonstrates that there is
more to Saturn than meets the eye.
The pictures show the effects of absorption and scattering of light
at different wavelengths by both atmospheric gas and clouds of differing
heights and thicknesses. They also show absorption of light by colored
particles mixed with white ammonia clouds in the planet's atmosphere.
Contrast has been enhanced to aid visibility of the atmosphere.
Cassini's narrow-angle camera took these four images over a period of
20 minutes on April 3, 2004, when the spacecraft was 44.5 million
kilometers (27.7 million miles) from the planet. The image scale is
approximately 267 kilometers (166 miles) per pixel. All four images
show the same face of Saturn.
In the upper left image, Saturn is seen in ultraviolet wavelengths
(298 nanometers); at upper right, in visible blue wavelengths (440
nanometers); at lower left, in far red wavelengths just beyond the
visible-light spectrum (727 nanometers; and at lower right, in
near-infrared wavelengths (930 nanometers).
The sliver of light seen in the northern hemisphere appears bright
in the ultraviolet and blue (top images) and is nearly invisible at
longer wavelengths (bottom images). The clouds in this part of the
northern hemisphere are deep, and sunlight is illuminating only the
cloud-free upper atmosphere. The shorter wavelengths are consequently
scattered by the gas and make the illuminated atmosphere bright, while
the longer wavelengths are absorbed by methane.
Saturn's rings also appear noticeably different from image to image,
whose exposure times range from two to 46 seconds. The rings appear dark
in the 46-second ultraviolet image because they inherently reflect little
light at these wavelengths. The differences at other wavelengths are
mostly due to the differences in exposure times.
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, D.C. 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, Colo.
For more information, about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov and the Cassini
imaging team home page, http://ciclops.org.
