Category: Saturn

Saturn’s moon Pandora. Image credit: NASA/JPL/SSI Click to enlarge
While close to Saturn in its orbit, Cassini stared directly at the planet to find Saturn’s moon Pandora in the field of view. The F ring shepherd moon is gliding towards the right in this scene. The F ring is thinly visible just above the main rings. Pandora is 84 kilometers (52 miles) across.
Near the lower left, some variation in the height of Saturn’s cloud tops can be detected. This effect is often visible near the terminator (the day and night boundary), where the Sun is at a very low angle above Saturn’s horizon.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 16, 2005, at a distance of approximately 1.3 million kilometers (800,000 miles) from Saturn. The image scale is about 8 kilometers (5 miles) per pixel on Saturn and about 6 kilometers (4 miles) per pixel on Pandora.

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

Spectrum indicating atmosphere over rings. Image credit: NASA/JPL/SSI/SWRI/UCL Click to enlarge
Data from the NASA/ESA/ASI Cassini spacecraft indicate that Saturn’s majestic ring system has its own atmosphere – separate from that of the planet itself.

During its close fly-bys of the ring system, instruments on Cassini have been able to determine that the environment around the rings is like an atmosphere, composed principally of molecular oxygen.
This atmosphere is very similar to that of Jupiter’s moons Europa and Ganymede.

The finding was made by two instruments on Cassini, both of which have European involvement: the Ion and Neutral Mass Spectrometer (INMS) has co-investigators from USA and Germany, and the Cassini Plasma Spectrometer (CAPS) instrument has co-investigators from US, Finland, Hungary, France, Norway and UK.

Saturn’s rings consist largely of water ice mixed with smaller amounts of dust and rocky matter. They are extraordinarily thin: though they are 250 000 kilometres or more in diameter they are no more than 1.5 kilometres thick.

Despite their impressive appearance, there is very little material in the rings – if the rings were compressed into a single body it would be no more than 100 kilometres across.

The origin of the rings is unknown. Scientists once thought that the rings were formed at the same time as the planets, coalescing out of swirling clouds of interstellar gas 4000 million years ago. However, the rings now appear to be young, perhaps only hundreds of millions of years old.

Another theory suggests that a comet flew too close to Saturn and was broken up by tidal forces. Possibly one of Saturn’s moons was struck by an asteroid smashing it to pieces that now form the rings.

Though Saturn may have had rings since it formed, the ring system is not stable and must be regenerated by ongoing processes, probably the break-up of larger satellites.

Water molecules are first driven off the ring particles by solar ultraviolet light. They are then split into hydrogen, and molecular and atomic oxygen, by photodissocation. The hydrogen gas is lost to space, the atomic oxygen and any remaining water are frozen back into the ring material due to the low temperatures, and this leaves behind a concentration of oxygen molecules.

Dr Andrew Coates, co-investigator for CAPS, from the Mullard Space Science Laboratory (MSSL) at University College London, said: “As water comes off the rings, it is split by sunlight; the resulting hydrogen and atomic oxygen are then lost, leaving molecular oxygen.

“The INMS sees the neutral oxygen gas, CAPS sees molecular oxygen ions and an ?electron view? of the rings. These represent the ionised products of that oxygen and some additional electrons driven off the rings by sunlight.”

Dr Coates said the ring atmosphere was probably kept in check by gravitational forces and a balance between loss of material from the ring system and a re-supply of material from the ring particles.

Last month, Cassini-Huygens mission scientists celebrated the spacecraft’s first year in orbit around Saturn. Cassini performed its Saturn Orbit Insertion (SOI) on 1 July 2004 after its six-year journey to the ringed planet, travelling over three thousand million kilometres.

The Cassini-Huygens mission is a co-operative project of NASA, ESA and ASI, the Italian space agency.

Original Source: ESA Science

Southern polar region of Rhea. Image credit: NASA/JPL/SSI Click to enlarge
Like the rest of Rhea’s surface, the southern polar region of this Saturn moon has been extensively re-worked by cratering over the eons. This close-up shows that most sizeable craters have smaller, younger impact sites within them. Near the left lies an intriguing gash.
The largest well-defined crater visible here is an oval-shaped impact toward the upper right. The crater is 115 by 91 kilometers (71 by 57 miles) in size.

Cassini acquired this view during a distant flyby of Rhea (1,528 kilometers, or 949 miles across) on July 14, 2005.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera at a distance of approximately 239,000 kilometers (149,000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 56 degrees. The image was obtained using a filter sensitive to wavelengths of infrared light centered at 930 nanometers. The image scale is about 1 kilometer (0.6 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 largest moon Titan. Image credit: NASA/JPL/SSI Click to enlarge
Titan’s equatorial latitudes are distinctly different in character from its south polar region, as this image shows.
The dark terrain, presumably lowland, seen here does not extend much farther south than about 30 degrees South. The successful Huygens probe landed in such a region. The Huygens probe is rotating into the light here, seeing the dawn of a new day.

The bright region toward the right side of Titan’s disk is Xanadu. This area is thought to consist of upland terrain that is relatively uncontaminated by the dark material that fills the lowland regions.

Near the moon’s south pole, and just eastward of the terminator, is the dark feature identified by imaging scientists as the best candidate (so far) for a past or present hydrocarbon lake on Titan (see Clouds in the Distance). Farther east of the lake-like feature, bright clouds arc around the pole. These clouds occupy a latitude range that is consistent with previously-seen convective cloud activity on Titan.

Titan is Saturn’s largest moon, at 5,150 kilometers (3,200 miles) across.

The image was taken with the Cassini spacecraft narrow angle camera on July 7, 2005, at a distance of approximately 1.3 million kilometers (800,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 60 degrees. The image was obtained using a filter sensitive to wavelengths of infrared light centered at 938 nanometers. The image scale is 7 kilometers (5 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

Faint filaments in Saturn’s atmosphere. Image credit: NASA/JPL/SSI Click to enlarge
Faint filaments in Saturn’s atmosphere spiral around two oval-shaped storms in a direction opposite to the winds which rotate around Southern Hemisphere hurricanes on Earth. One storm is seen near the lower right, and the other is near the lower left above a much darker storm.
Atmospheric scientists do not yet fully understand what these filaments are, but some possible explanations have been proposed. The filaments might represent material connecting the spots if the two have recently split from a single storm. The spirals could also represent wind flow in the atmosphere. Further investigation by Cassini imaging scientists is likely to clarify the precise nature of the filaments.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 6, 2005, at a distance of approximately 2.4 million kilometers (1.5 million miles) from Saturn using a filter sensitive to wavelengths of infrared light centered at 750 nanometers. The image scale is 14 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 turbulent atmosphere. Image credit: NASA/JPL/SSI Click to enlarge
Saturn’s turbulent atmosphere is reminiscent of a Van Gogh painting in this view from Cassini. However, unlike the famous impressionist painter, Cassini records the world precisely as it appears to the spacecraft’s cameras.
The feathery band that cuts across from the upper left corner to the right side of this scene has a chevron, or arrow, shape near the right. The center of the chevron is located at the latitude (about 28 degrees South) of an eastward-flowing zonal jet in the atmosphere. Counter-flowing eastward and westward jets are the dominant dynamic features seen in the giant planet atmospheres. A chevron-shaped feature with the tip pointed east means that this is a local maximum in the eastward wind and a region of horizontal wind shear, where clouds to the north and south of the jet are being swept back by the slower currents on the sides of the jet.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 6, 2005, at a distance of approximately 2.5 million kilometers (1.5 million miles) from Saturn using a filter sensitive to wavelengths of infrared light centered at 727 nanometers. The image scale is 14 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 anti-hurricanes. Image credit: NASA/JPL/SSI Click to enlarge
Vortices mingle amidst other turbulent motions in Saturn’s atmosphere in these two comparison images. The image on the right was taken about two Saturn rotations after the image on the left.

Both views show latitudes from minus 23 degrees to minus 42 degrees. The region below center in these images (at minus 35 degrees) has seen regular storm activity since Cassini first approached Saturn in early 2004. Cassini investigations of the atmosphere from February to October 2004 showed that most of the oval-shaped storms in the latitude region near minus 35 degrees rotate in a counter-clockwise direction, with smaller storms occasionally merging into larger ones (see Saturn Movie and Saturn Movie Closeup for a movie of storm activity in this region).

On Earth, hurricanes in the Southern Hemisphere rotate clockwise. Thus, the storms in these images of Saturn’s southern latitudes could be called “anti-hurricanes.” This backwards spiraling (compared to Earth) is common on the giant planets.

The images were taken with the Cassini spacecraft narrow-angle camera on July 4 and 5, 2005, using a filter sensitive to wavelengths of infrared light centered at 750 nanometers. During this time, Cassini’s distance from Saturn was approximately 2.4 million kilometers (1.5 million miles). The image scale is about 14 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 moon Epimetheus just beneath the ring. Image credit: NASA/JPL/SSI Click to enlarge.
Saturn’s moon Epimetheus is seen here from just beneath the ring plane, along with Saturn’s intriguing F ring. The bright, knotted core of the F ring is flanked on both sides by thin, dusty strands. The outer part of the A ring is visible at the left. Epimetheus is 116 kilometers (72 miles) across.

Part of the little moon’s night side is illuminated by reflected light from the planet. For a closer view of Epimetheus see Epimetheus: Up-Close and Colorful.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 30, 2005, at a distance of approximately 1.8 million kilometers (1.1 million miles) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 93 degrees. Resolution in the original image was 11 kilometers (7 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

False color image of Mimas. Image credit: NASA/JPL/SSI Click to enlarge
On its recent close flyby of Mimas, the Cassini spacecraft found the Saturnian moon looking battered and bruised, with a surface that may be the most heavily cratered in the Saturn system.

The Aug. 2 flyby of Saturn’s “Death Star” moon returned eye-catching images of its most distinctive feature, the spectacular 140-kilometer diameter (87-mile) landslide-filled Hershel crater. Numerous rounded and worn-out craters, craters within other craters and long grooves reminiscent of those seen on asteroids are also seen in the new images.

The new Mimas images are available at http://saturn.jpl.nasa.gov, http://www.nasa.gov/cassini and http://ciclops.org . Also available is an approach movie showing Mimas, and a zoom and pan across the surface of one of the highest resolution images.

The closest images show Mimas, measuring 397 kilometers (247 miles) across, in the finest detail yet seen. One dramatic view acquired near Cassini’s closest approach shows the moon against the backdrop of Saturn’s rings. A false color composite image reveals a region in blue and red of presumably different composition or texture just west of, and perhaps related to, the Hershel crater.

Scientists hope that analysis of the images will tell them how many crater-causing impactors have coursed through the Saturn system, and where those objects might have come from. There is also the suspicion, yet to be investigated, that the grooves, first discovered by NASA’s Voyager spacecraft but now seen up close, are related to the giant impact that caused the biggest crater of all, Herschel, on the opposite side of the moon.

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, 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.

Original Source: NASA News Release

Saturn’s auroral emissions. Image credit: NASA/JPL/University of Colorado. Click to enlarge
New images of Saturn obtained by a University of Colorado at Boulder-led team on June 21 using an instrument on the Cassini spacecraft show auroral emissions at its poles similar to Earth’s Northern Lights.

Taken with the Ultraviolet Imaging Spectrograph aboard the Cassini orbiter, the two UV images, invisible to the human eye, are the first from the Cassini-Huygens mission to capture the entire “oval” of the auroral emissions at Saturn’s south pole. They also show similar emissions at Saturn’s north pole, according to CU-Boulder Professor Larry Esposito, principal investigator of the UVIS instrument built at CU-Boulder’s Laboratory for Atmospheric and Space Physics, and Professor Wayne Pryor of Central Arizona College, a UVIS team member and former CU graduate student.

In the false-color images, blue represents aurora emissions from hydrogen gas excited by electron bombardment, while red-orange represents reflected sunlight. The images show that the aurora lights at the polar regions respond rapidly to changes in the solar wind, said the researchers. Previous images have been taken closer to the equator, making it difficult to see the polar regions.

Major changes in the emissions inside the Saturn south-pole aurora are evident by comparing the two images, which were taken about one hour apart, they said. The brightest spot in the left aurora fades, and a bright spot appears in the middle of the aurora in the second image.

Made by slowly scanning the UVIS instrument across the planet, the images also contain more than 2,000 wavelengths of spectral information within each picture element. Researchers will use the wavelength information to study Saturn’s auroras, gases, and hazes and their changing distributions.

The UVIS observation team includes researchers from CU-Boulder, NASA’s Jet Propulsion Laboratory, Central Arizona College and the University of Southern California.

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 Space Science Mission Directorate in Washington, D.C.

More information on the Cassini-Huygens mission is available at the following Web sites: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

Original Source: CU-Boulder News Release