[酷图] 卡西尼号最新拍摄的土星风暴（3月26日发布）

土星风暴

GIF 动画: 512x512, 30 帧

High Winds Aloft on Saturn

Wind-blown clouds and hazes high in Saturn's atmosphere are captured in a movi
e made from images taken by the Cassini narrow angle camera between Feb. 15 an
d Feb. 19, 2004. The images were made using a filter sensitive to a narrow ran
ge of wavelengths centered at 889 nanometers where methane in Saturn's atmosph
ere absorbs sunlight. Cassini was 65.6 million kilometers (40.7 million miles)
from Saturn when the images, reduced in size by a factor of two onboard the s
pacecraft, were taken. The resulting image scale is approximately 786 kilomete
rs (420 miles) per pixel.

This is the first movie ever made showing Saturn in these near-infrared wavele
ngths. The movie, consisting of 30 stacked images, spans five days and capture
s five complete but non-consecutive Saturn rotations. The direction of motion
is prograde, or left to right. Each 10.6 hour Saturn rotation is evenly sample
d by six images. In `movie time', there is 0.25 second between each of the six
images in an individual rotation, and one second between rotations. After eac
h rotation sequence, the planet can be seen to grow slightly in the field of v
iew.

Cassini has three filters designed to sense different heights of clouds and ha
zes in Saturn's atmosphere. Any light detected by cameras using the 889 nanome
ter filter is reflected very high in the atmosphere, before the light is absor
bed. Thus, the bright areas in these images represent high hazes and clouds ne
ar the top of Saturn's troposphere.

In the movie, atmospheric motions can be seen most clearly in the equatorial r
egion and at other southern latitudes as well. Saturn's equatorial region seem
s disturbed in the same way that it has been for the past decade, as revealed
by observations from the Hubble Space Telescope. Researchers have speculated t
hat the bright cloud patterns there are associated with water-moist convection
arising from a deeper atmospheric level where water condenses on Saturn, and
rising to levels at or above the visible cloud tops. Close analysis of future
images by scientists on the Cassini-Huygens mission should help determine if t
his is the case.

Saturn's rings are extremely overexposed in these images. Because the range of
wavelengths for this spectral filter is narrow, and because most of this ligh
t is absorbed by Saturn, the disk of Saturn is inherently faint and the exposu
res required are quite long (22 seconds). The rings do not strongly absorb at
these wavelengths, and so reflect more light and are overexposed compared to t
he atmosphere. Orbiting moons in the images were manually removed during proce
ssing.

The Cassini-Huygens mission is a cooperative project of NASA, the European Spa
ce Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a divis
ion of the California Institute of Technology in Pasadena, manages the Cassini
-Huygens mission for NASA's Office of Space Science, Washington, D.C. The imag
ing team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jp
l.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Credit: NASA/JPL/Space Science Institute
Released: March 26, 2004 (PIA 05384)
Image/Caption Information