Crescents Slice the Darkness in 'Farewell Jupiter' Picture by Cassini

Lori Stiles
May 31, 2001

Jupiter shines as a crescent, with a much smaller crescent moon Io by its side, in a color-composite picture made from images taken by NASA's Cassini spacecraft looking back at the Jupiter after flying past it five months ago.

That "farewell, Jupiter" image plus a color movie clip of glowing features on Io during an eclipse are now available online from the Cassini Imaging Science team at the University of Arizona, Tucson, at and from NASA's Jet Propulsion Laboratory, Pasadena, Calif., at

The eclipse movie is being presented at meetings of the American Geophysical Union in Boston today. In the sequence of images used to create it, Cassini caught Io's auroras in motion and detected emissions at previously unknown wavelengths. Red glows from oxygen atoms and blue glows from sulfur dioxide molecules in the images, along with thermal glows from hot lava at several active volcanoes.

Cassini Imaging Team leader Carolyn C. Porco says in a message posted today on the Cassini Imaging Team web site, Ciclops: "Cassini's Jupiter flyby officially came to a close at the end of March, when routine imaging of the planet and its satellites and rings ceased and the spacecraft was buttoned up for the cruise to Saturn.

"In all, about 26,000 images were collected -- a bounty that is Voyager-class in size. Our initial findings to date, recorded on the pages of this website (Imaging Diary: Jupiter) indicate promising new directions of research in the study of Jovian atmospheric dynamics, the production of polar stratospheric haze, the nature of Jovian lightning, auroral processes in the planet's northern and southern hemispheres, the interactions between Jupiter's magnetic field and the tenuous atmospheres of some of the Galilean satellites, and much more. The results from the other Cassini instruments have proven equally rewarding. Cassini's traverse through the Jupiter system was every bit the whirlwind we expected. Scientists will surely be poring over these data for years to come.

"Cassini left the Jovian system on a trajectory that kept its view of Jupiter nearly constant with respect to the Sun. That view is shared with all of you today in a release of a mosaic of images taken by the narrow angle camera on January 15, 2001, about two weeks after the spacecraft's closest approach to the planet. No human has yet been far enough from the Sun to enjoy such a view with his own eyes. And until we bodily transport ourselves across the solar system and beyond the orbit of Jupiter, no one ever will. Perspectives like this come only as a result of our explorations with robotic space travelers like Cassini.

"We are also releasing today a color rendition of an earlier black and white Io eclipse movie, making it easier to see and distinguish the different glows emanating from the moon when in the dark of Jupiter's shadow.

"Now, Cassini scientists are turning their attentions towards preparations for Cassini's arrival at Saturn in July, 2004. To those of us who have been part of this mission for the past decade, it seems only around the corner."

Cassini passed its closest to Jupiter on Dec. 30, 2000, gaining a gravitational boost for reaching its main destination, Saturn, in 2004. More information about joint studies of Jupiter by Cassini and NASA's Galileo spacecraft, which has been orbiting Jupiter for more than five years, is available at .

Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini and Galileo missions for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.


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