Category: Saturn

Mimas and the small Trojan moon Helene. Image credit: NASA/JPL/SSI. Click to enlarge
Gazing across the ringplane, the Cassini spacecraft spots a Saturn-lit Mimas and the tiny Trojan moon Helene. Only the bright crescent on Mimas’ eastern limb is lit by the Sun; the moon’s night side is illuminated by Saturnshine, or “greylight” as it is called by imaging scientists.

Helene (32 kilometers, or 20 miles across) shares the orbit of Dione (not pictured here) and is visible as a speck to the left of Mimas. This view shows the Saturn-facing side of Mimas (397 kilometers, or 247 miles across).

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 2, 2005, at a distance of approximately 2 million kilometers (1.2 million miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 121 degrees. Helene was about 2.2 million kilometers (1.4 million miles) distant. The image scale is 12 kilometers (7 miles) per pixel on Mimas.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Saturn’s icy F ring. Image credit: NASA/JPL/SSI Click to enlarge
The searing arc of light seen here is Saturn’s icy F ring, seen nearly edge-on. In the background, Rhea (1,528 kilometers, or 949 miles across) is lit by reflected light from Saturn and the rings, with only the slightest sliver of light at its bottom being from direct sunlight.

The faint material surrounding the F ring likely lies in the planet’s equatorial plane, extending radially farther out and in from the main F ring core. A smaller fraction of this material could be vertically extended, and Cassini’s investigations should help to clarify this.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 30, 2005, at a distance of approximately 689,000 kilometers (428,000 miles) from Saturn. The image scale is approximately 4 kilometers (2 miles) per pixel.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Enceladus plume. Image credit: NASA/JPL/UA Click to enlarge
Cassini observations by several instruments have revealed the source of Saturn’s broadest and faintest ring. Recent observations show that tiny particles of frozen water ice are streaming outward into space from the south polar region of the moon Enceladus.

The source of geological activity on Enceladus is a mystery. “We’re amazed to see ice geysers on this little world that was thought to be cold and dead long ago,” commented Dr. Dale Cruikshank of NASA Ames Research center, a member of the visual and infrared mapping spectrometer team. “Some unexpected process is vigorously heating the interior of Enceladus, especially the south polar region, and causing the ejection of the plumes of ice particles.”

As the icy plumes jet out from the moon, the larger particles probably follow paths that mostly bring them back to the surface, while the smaller particles are nudged by sunlight into orbits around Saturn.

“Most of these small particles probably re-impact the moon, but the smallest ones eventually disperse as a result of radiation (light) pressure and interactions with Saturn’s magnetosphere to form the broad E ring,” said Dr. Mark Showalter of the SETI Institute, Mountain View, Calif. Thus, the E ring is currently being regenerated by some kind of geological activity in the interior of Enceladus.

During the Cassini spacecraft’s flyby on Nov. 26, the visual and infrared mapping spectrometer instrument measured the spectrum of the polar plumes of Enceladus. “We see a very clear signature of small ice particles in the plume data, in the form of a strong absorption band at 2.9 microns in an otherwise featureless spectrum,” said Dr. Phil Nicholson, professor of astronomy at Cornell University, Ithaca, N.Y. Nicholson is a member of the visual and infrared mapping spectrometer science team.

The visual and infrared mapping spectrometer images of Enceladus show not only the plume over the south pole, but also the dark side of the moon, silhouetted against a foggy background of light from the E Ring. Measurements of the spectrum show a very similar signature of small ice particles to that in the plumes, confirming earlier expectations that Enceladus is indeed the source of the E ring.

Preliminary analyses suggest that the average size of the particles in the plume is about 10 microns (1/100,000 of a meter), whereas the particles in the E ring are about three times smaller. The sunlit surface of Enceladus itself is also composed of water ice, but with a much larger grain size than the plume.

Original Source: NASA/JPL/SSI News Release

Shepherd moons, Prometheus and Pandora. Image credit: NASA/JPL/SSI Click to enlarge
This spectacular image shows Prometheus (at left) and Pandora (at right), with their flock of icy ring particles (the F ring) between them. Pandora is exterior to the ring, and closer to the spacecraft here. Each of the shepherd satellites has an unusual shape, with a few craters clearly visible.

The effect of Prometheus (102 kilometers, or 63 miles across) on the F ring is visible as it pulls material out of the ring when it is farthest from Saturn in its orbit. Pandora is 84 kilometers (52 miles) across.

The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Oct. 29, 2005, at a distance of approximately 459,000 kilometers (285,000 miles) from Pandora and 483,500 kilometers (300,500 miles) from Prometheus. The image scale is 3 kilometers (2 miles) per pixel on Pandora and 3 kilometers (2 miles) per pixel on Prometheus. The view was acquired from about a third of a degree below the ringplane.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Gaps in Saturn’s rings. Image credit: NASA/JPL/SSI Click to enlarge
Saturn’s rings throw imposing shadows and relegate parts of the planet’s northern regions to darkness. Three thin and bright arcs in this scene represent three well-known gaps in the immense ring system. From bottom to top here (and widest to thinnest) they are the Cassini Division, the Encke Gap and the Keeler Gap.

The image was taken in infrared light (752 nanometers) using the Cassini spacecraft wide-angle camera on Oct. 29, 2005, at a distance of approximately 446,000 kilometers (277,000 miles) from Saturn. The image scale is 23 kilometers (14 miles) per pixel. The image was contrast enhanced to improve visibility of features in the atmosphere.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Saturn’s rings very close to edge-on. Image credit: NASA/JPL/SSI Click to enlarge
Viewing Saturn’s rings very close to edge-on produces some puzzling effects, as these two images of the F ring demonstrate.

The upper image was acquired from less than a tenth of a degree beneath the ringplane and shows a mysterious bulge. Such a feature has not been seen previously by the Cassini spacecraft from this angle. It is possible that, because of the very shallow viewing angle, the Cassini spacecraft’s view takes a long path through the ring, making very faint material visible. It also may be that an embedded object of a kilometer or so in size stirs up the neighboring ring particles to create a bulge. Alternatively, an impact into an embedded moonlet that was covered with debris could produce a cloud like this.

Images taken by the Voyager spacecrafts showed clumps that might have been produced in these ways. Cassini’s investigations will help to determine the vertical extent of such clumps and understand their origins.

The lower image was obtained from less than a hundredth of a degree beneath the ringplane. Across the center of the rings is a dark lane, giving them an appearance not unlike that of a spiral galaxy, seen edge-on.

Both images were taken using the clear spectral filters (predominantly visible light) on the Cassini spacecraft narrow-angle camera. The images have been magnified by a factor of two.

The top image was obtained at a distance of 3.6 million kilometers (2.2 million miles) from Saturn on Nov. 11, 2005 and shows wispy fractures on Dione’s trailing hemisphere. The image scale is 22 kilometers (14 miles) per pixel. The bottom image was acquired at a distance of 2.5 million kilometers (1.6 million miles) from Saturn on Nov. 5, 2005. The image scale is 15 kilometers (9 miles) per pixel.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Saturn’s moons, Rhea and Dione. Image credit: NASA/JPL/SSI Click to enlarge
Saturn’s sibling moons, Rhea and Dione, pose for the Cassini spacecraft in this view.

Even at this distance, it is easy to see that Dione (below) appears to have been geologically active in the more recent past, compared to Rhea (above). Dione’s smoother surface and linear depressions mark a contrast with Rhea’s cratered terrain.

Sunlit terrain seen on Rhea (1,528 kilometers, or 949 miles across) is on the moon’s Saturn-facing hemisphere. Lit terrain on Dione (1,126 kilometers, or 700 miles across) is on that moon’s leading hemisphere. North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 1, 2005, at a distance of approximately 1.8 million kilometers (1.1 million miles) from Rhea and 1.2 million kilometers (800,000 miles) from Dione. The image scale is 11 kilometers (7 miles) per pixel on Rhea and 7 kilometers (4 miles) per pixel on Dione.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Saturn’s crescent. Image credit: NASA/JPL/SSI Click to enlarge
Feathery cloud bands fill Saturn’s graceful crescent. Features in the atmosphere are visible all the way to the terminator, the boundary between night and day, where the Sun’s rays are coming in almost horizontally.

Because it is possible to see down to the same level, regardless of how high the Sun is above the horizon, this indicates that the atmosphere above the clouds is relatively clear.

The dark line across the top of the image is the nearly edge-on ringplane.

The image was taken in infrared light (centered at 728 nanometers) with the Cassini spacecraft wide-angle camera on Oct. 31, 2005, at a distance of approximately 1.2 million kilometers (800,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 131 degrees. Image scale is 69 kilometers (43 miles) per pixel. The image was contrast enhanced to improve visibility of features in the atmosphere.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

False-color views of Saturn’s cratered, icy moons, Rhea and Dione. Image credit: NASA/JPL/SSI Click to enlarge
Wrapping up a phenomenally successful year of observing Saturn’s icy moons, the Cassini mission is releasing a flood of new views of the moons Enceladus, Dione, Rhea, Hyperion and Iapetus.

The moons and their intricacies are being highlighted at a news briefing today at the American Geophysical Union meeting in San Francisco.

Several new images of Rhea, a moon measuring 1,528 kilometers (949 miles) across, were taken during Cassini’s most recent close flyby on November 26. During the encounter, Cassini dipped to within 500 kilometers (310 miles) of Rhea’s surface.

Additional new images include two “zoomable” mosaics of Rhea and Hyperion at high resolution; false-color views revealing compositional variation on the surfaces of Hyperion, Dione and Rhea; two movies reproducing Cassini’s exciting encounters with Iapetus and Hyperion; and dazzling new images of the plumes of Enceladus, including a time-lapse movie.

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 Science Mission Directorate, Washington. 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.

The image products being released include large mosaics, movies and false-color views. They are available at: http://saturn.jpl.nasa.gov , http://www.nasa.gov/cassini and http://ciclops.org .

Original Source: NASA News Release

The southwest limb of Saturn. Image credit: NASA/JPL/SSI Click to enlarge
This brooding portrait shows the southwest limb (edge) of the cold gas giant and the thread-like cloud features lurking there. The limb appears smooth, but at the terminator (the boundary between light and dark) and at higher resolution, variations in cloud height can cause shadows that are visible to Cassini (see Such Great Heights).

The image was taken in visible, red light with the Cassini spacecraft wide-angle camera on Oct. 30, 2005, at a distance of approximately 401,000 kilometers (249,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 155 degrees. Image scale is 20 kilometers (13 miles) per pixel. The image was contrast enhanced to improve visibility of features in the atmosphere.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release