Four Ways to See Saturn

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, saturn.jpl.nasa.gov/ and the Cassini

imaging team home page, ciclops.org/.

 

credit: NASA/JPL/Space Science Institute

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