Category: Saturn

The great eye of Mimas. Image credit: NASA/JPL/SSI Click to enlarge
The great eye of Saturn’s moon Mimas (MY-muss), a 130-kilometer-wide (80-mile) impact crater called Herschel, stares out from the battered moon in this raw image taken by the Cassini spacecraft during a flyby on Aug. 2.

The Herschel crater is the moon’s most prominent feature, and the impact that formed it probably nearly destroyed Mimas. Cassini flew by Mimas at 62,700 kilometers (38,800 miles) above the moons surface, bringing it closer to the little moon than ever before.

Original Source: NASA/JPL/SSI News Release

Saturn’s moon Rhea. Image credit: NASA/JPL/SSI. Click to enlarge
This view of Saturn’s moon Rhea shows the tremendous bright splat that coats much of the moon’s leading hemisphere. The bright feature may be impact-related and is visible in other Cassini images of Rhea (see Diversity of Impacts). Rhea is 1,528 kilometers (949 miles) across.

North on Rhea is up in this view.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on June 25, 2005, at a distance of approximately 1.1 million kilometers (700,000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of less than one degree. Resolution in the original image was 7 kilometers (4 miles) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility.

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 swirling clouds. Image credit: NASA/JPL/SSI. Click to enlarge
Believe it or not, this extreme close-up of Saturn’s swirling clouds was acquired from more than one million kilometers (621,370 miles) from the gas giant planet. The rings’ image is severely bent by atmospheric refraction as they pass behind the planet.
The dark region in the rings is the 4,800-kilometer-wide (2,980 mile) Cassini Division.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 25, 2005, at a distance of approximately 1 million kilometers (600,000 miles) from Saturn. The image scale is 6 kilometers (4 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

Map showing observed temperatures at Enceladus. Image credit: NASA/JPL/GSFC. Click to enlarge
Saturn’s tiny icy moon Enceladus, which ought to be cold and dead, instead displays evidence for active ice volcanism.

NASA’s Cassini spacecraft has found a huge cloud of water vapor over the moon’s south pole, and warm fractures where evaporating ice probably supplies the vapor cloud. Cassini has also confirmed Enceladus is the major source of Saturn’s largest ring, the E-ring.

“Enceladus is the smallest body so far found that seems to have active volcanism,” said Dr. Torrence Johnson, Cassini imaging-team member at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Enceladus’ localized water vapor atmosphere is reminiscent of comets. ‘Warm spots’ in its icy and cracked surface are probably the result of heat from tidal energy like the volcanoes on Jupiter’s moon Io. And its geologically young surface of water ice, softened by heat from below, resembles areas on Jupiter’s moons, Europa and Ganymede.”

Cassini flew within 175 kilometers (109 miles) of Enceladus on July 14. Data collected during that flyby confirm an extended and dynamic atmosphere. This atmosphere was first detected by the magnetometer during a distant flyby earlier this year.

The ion and neutral mass spectrometer and the ultraviolet imaging spectrograph found the atmosphere contains water vapor. The mass spectrometer found the water vapor comprises about 65 percent of the atmosphere, with molecular hydrogen at about 20 percent. The rest is mostly carbon dioxide and some combination of molecular nitrogen and carbon monoxide. The variation of water vapor density with altitude suggests the water vapor may come from a localized source comparable to a geothermal hot spot. The ultraviolet results strongly suggest a local vapor cloud.

The fact that the atmosphere persists on this low-gravity world, instead of instantly escaping into space, suggests the moon is geologically active enough to replenish the water vapor at a slow, continuous rate.

“For the first time we have a major clue not only to the role of water at the icy moons themselves, but also to its role in the evolution and dynamics of the Saturn system as a whole,” said Dr. Ralph L. McNutt, ion and neutral mass spectrometer-team member, Johns Hopkins University Applied Physics Laboratory, Laurel, Md.

Images show the south pole has an even younger and more fractured appearance than the rest of Enceladus, complete with icy boulders the size of large houses and long, bluish cracks or faults dubbed “tiger stripes.”

Another Cassini instrument, the composite infrared spectrometer, shows the south pole is warmer than anticipated. Temperatures near the equator were found to reach a frigid 80 degrees Kelvin (minus 316 Fahrenheit), as expected. The poles should be even colder because the Sun shines so obliquely there. However, south polar average temperatures reached 85 Kelvin (minus 307 Fahrenheit), much warmer than expected. Small areas of the pole, concentrated near the “tiger stripe” fractures, are even warmer: well over 110 Kelvin (minus 261 Fahrenheit) in some places.

“This is as astonishing as if we’d flown past Earth and found that Antarctica was warmer than the Sahara,” said Dr. John Spencer, team member of the composite infrared spectrometer, Southwest Research Institute, Boulder, Colo.

Scientists find the temperatures difficult to explain if sunlight is the only heat source. More likely, a portion of the polar region, including the “tiger stripe” fractures, is warmed by heat escaping from the interior. Evaporation of this warm ice at several locations within the region could explain the density of the water vapor cloud detected by other instruments. How a 500-kilometer (310-mile) diameter moon can generate this much internal heat and why it is concentrated at the south pole is still a mystery.

Cassini’s cosmic dust analyzer detected a large increase in the number of particles near Enceladus. This observation confirms Enceladus is a source of Saturn’s E-ring. Scientists think micrometeoroids blast the particles off, forming a steady, icy, dust cloud around Enceladus. Other particles escape, forming the bulk of the E ring.

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. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.

Additional information and graphics on these results are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Original Source: NASA News Release

Tethys and Mimas circling Saturn. Image credit: NASA/JPL/SSI. Click to enlarge
Far above the howling winds of Saturn, its icy moons circle the planet in silence. Mimas is seen near the upper right, while Tethys hovers at the bottom. Dark shadows cast by the see-through rings slice across the northern hemisphere. Mimas is 397 kilometers (247 miles) across. Tethys is 1,071 kilometers (665 miles) across.
The dark, doughnut-shaped storm near the south pole is at least 1,600 kilometers (1,000 miles) across and could easily swallow any of Saturn’s moons except giant Titan (5,150 kilometers, 3,200 miles across).

The image was taken with the Cassini spacecraft wide-angle camera on June 21, 2005, through a filter sensitive to wavelengths of infrared light centered at 752 nanometers at a distance of approximately 2.2 million kilometers (1.3 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 53 degrees. The image scale is 125 kilometers (78 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 team is based at the Space Science Institute, 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 splendid rings made visible by sunlight. Image credit: NASA/JPL/SSI. Click to enlarge
This view shows the unlit side of Saturn’s splendid rings made visible by sunlight filtering through the rings from the lit side. Light from the illuminated side of the rings brightens the night side of the planet’s southern hemisphere with “ringshine” (seen here at lower right). The feeble glow from transmitted light dimly illuminates the planet’s northern half.
Saturn’s shadow stretches across the rings toward lower left.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 8, 2005, at a distance of approximately 477,000 kilometers (296,000 miles) from Saturn. The image scale is 25 kilometers (15 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 team is based at the Space Science Institute, 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

The southern polar terrain of Enceladus. Image credit: NASA/JPL/SSI. Click to enlarge
NASA’s Cassini spacecraft has obtained new, detailed images of the south polar region of Saturn’s moon Enceladus. The data reveal distinctive geological features and the most youthful terrain seen on the moon. These findings point to a very complex evolutionary history for Saturn’s brightest, whitest satellite.

Cassini’s July 14 flyby brought it within 175 kilometers (109 miles) of the surface of the icy moon. The close encounter revealed a landscape near the south pole almost entirely free of impact craters. The area is also littered with house-sized ice boulders carved by unique tectonic patterns found only in this region of the moon.

As white as fresh snow, Enceladus has the most reflective surface in the solar system. Previous Cassini flybys revealed Enceladus, in contrast to Saturn’s other icy moons, has lightly cratered regions, fractured plains and wrinkled terrain.

The new findings add to the story of a body that has undergone multiple episodes of geologic activity spanning a considerable portion of its lifetime. The moon’s southernmost latitudes have likely seen the most recent activity.

These same latitudes may also bear the scars of a shift in the moon’s spin rate. If true, this speculation may help scientists understand why Enceladus has a tortured-looking surface, with pervasive crisscrossing faults, folds and ridges. The most remarkable images show ice blocks about 10 to 100 meters (33 to 328 feet) across in a region that is unusual in its lack of the very fine-grained frost that seems to cover the rest of Enceladus.

“A landscape littered with building-sized blocks was not expected,” said Dr. Peter Thomas, an imaging-team member from Cornell University, Ithaca, N.Y. “The minimal cover of finer material and the preservation of small, crossing fracture patterns in the surrounding areas indicate that this region is young compared to the rest of Enceladus.”

False color composites of this region, created from the most recent images, show the largest exposures of coarse-grained ice fractures seen anywhere on the moon, which also supports the notion of a young surface at southern latitudes. Some of the latest images may hint at the answer. The images revealed additional examples of a distinctive “Y-shaped” tectonic feature on Enceladus. In this unusual element, parallel ridges and valleys appear to systematically fold and deform around the south polar terrains.

“These tectonic features define a boundary that isolates the young, south polar terrains from older terrains on Enceladus,” noted Dr. Paul Helfenstein, an associate of the imaging team also at Cornell University. “Their placement and orientation may tell us a very interesting story about the way the rotation of Enceladus has evolved over time and what might have provided the energy to power the geologic activity that has wracked this moon.”

The apparent absence of sizable impact craters also suggests the south pole is younger than other terrain on Enceladus. All these indications of youth are of great interest to scientists, who have long suspected Enceladus as one possible source of material for Saturn’s extensive and diffuse E ring, which coincides with the moon’s orbit. Young terrain requires a means to generate the heat needed to modify the surface. Other Cassini instrument teams are working to understand data about the temperature, composition, particles and magnetic field. Together with image interpretation, these data can create a more complete picture.

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. 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.

These Cassini images are available on the Web at: http://www.nasa.gov/cassini , http://saturn.jpl.nasa.gov and http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Image depicting radio emissions at Saturn. Image credit: NASA/JPL/University of Iowa. Click to enlarge
Saturn’s radio emissions could be mistaken for a Halloween sound track.

That’s how two researchers describe their recent findings, published in the July 23 issue of the Geophysical Research Letters. Their paper is based on data from the Cassini spacecraft radio and plasma wave science instrument. The study investigates sounds that are not just eerie, but also descriptive of a phenomenon similar to Earth’s northern lights.

“All of the structures we observe in Saturn’s radio spectrum are giving us clues about what might be going on in the source of the radio emissions above Saturn’s auroras,” said Dr. Bill Kurth, deputy principal investigator for the instrument. He is with the University of Iowa, Iowa City. Kurth made the discovery along with Principal Investigator Don Gurnett, a professor at the University. “We believe that the changing frequencies are related to tiny radio sources moving up and down along Saturn’s magnetic field lines.”

Samples of the resulting sounds can be heard at http://www.nasa.gov/cassini , http://saturn.jpl.nasa.gov and http://www-pw.physics.uiowa.edu/cassini/ .

The radio emissions, called Saturn kilometric radiation, are generated along with Saturn’s auroras, or northern and southern lights. Because the Cassini instrument has higher resolution compared to a similar instrument on NASA’s Voyager spacecraft, it has provided more detailed information on the spectrum and the variability of radio emissions. The high-resolution measurements allow scientists to convert the radio waves into audio recordings by shifting the frequencies down into the audio frequency range.

The terrestrial cousins of Saturn’s radio emissions were first reported in 1979 by Gurnett, who used an instrument on the International Sun-Earth Explorer spacecraft in Earth orbit. Kurth said that despite their best efforts, scientists still haven’t agreed on a theory to fully explain the phenomenon.

They will get another chance to solve the radio emission puzzle beginning in mid-2008 when Cassini will fly close to, or possibly even through, the source region at Saturn. Gurnett said, ?It is amazing that the radio emissions from Earth and Saturn sound so similar.?

Other contributors to the paper include University of Iowa scientists George Hospodarsky and Baptiste Cecconi; Mike Kaiser (currently at Goddard Space Flight Center, Greenbelt, Md.); French scientists Philippe Louarn, Philippe Zarka and Alain Lecacheux; and Austrian scientists Helmut Rucker and Mohammed Boudjada.

Cassini, carrying 12 scientific instruments, on June 30, 2004, became the first spacecraft to orbit Saturn. It is conducting a four-year study of the planet, its rings and many moons. The spacecraft carried the Huygens probe, a six-instrument European Space Agency probe that landed on Titan, Saturn’s largest moon, in January 2005.

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. JPL designed, developed and assembled the Cassini orbiter. The radio and plasma wave science team is based at the University of Iowa, Iowa City.

For information on the Cassini mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini

Original Source: NASA News Release

Saturn appears as a bright object to the left of the Sun. Image credit: SOHO. Click to enlarge
In this SOHO image taken July 21, 2005, the Sun is represented by the white circle in the center. Saturn is the bright object to the left of the Sun. Interestingly, the streak accompanying Saturn is not the rings but a distortion caused by Saturn’s brightness.

Saturn is approaching “superior conjunction,” that is, it will be almost directly behind the Sun from Earth — thus the Cassini spacecraft, in orbit around Saturn, will not be able to send or receive transmissions normally. Regular science data collection has been temporarily suspended.

As Cassini passes closest by the limb (edge) of the Sun on July 24 PDT, communications will be impossible because of the Sun’s radio noise. The spacecraft will regain full communication with Earth on July 27, once again returning Saturn science data. In the meantime, controllers are sending approximately 100 commands per day to test communication status. Cassini radio scientists are taking advantage of this opportunity to study the Sun’s corona from its effects on the radio signals that reach Earth.

SOHO (Solar and Heliospheric Observatory Satellite) orbits the Sun parked in one of the five gravitational-neutral spots, called Lagrange Points. This specific spot, called L1, stays in the same place relative to the Sun and the Earth, offering a continuously uninterrupted view of the Sun.

Saturn is not in sight again until the evening of July 24. After that date, it will be to the RIGHT of the sun.

For more information on “superior conjunction,” visit: http://www.jpl.nasa.gov/basics/bsf1-2.html#conj .

For more information on the Lagrange Points, visit: http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html

For more information on SOHO, visit: http://sohowww.nascom.nasa.gov/ .

Finally, the latest SOHO images are available at: http://sohowww.nascom.nasa.gov/data/realtime/c3/1024/latest.gif .

Original Source: NASA/JPL/SSI News Release

F ring appears against the planet and above Prometheus. Image credit: NASA/JPL/SSI. Click to enlarge
Cassini peers through the icy particles that comprise Saturn’s rings as Prometheus sits perched on the planet’s limb (edge). The rings cast shadows on the planet, with darker regions corresponding to places where the ring material is denser. The narrow dense regions are created by gravitational resonances with moons, like Prometheus, that orbit near the rings. Prometheus is 102 kilometers (63 miles) across.
The thin, bright core of the F ring can be seen against the planet and above Prometheus.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 3, 2005, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Saturn. The image scale is 13 kilometers (8 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 team is based at the Space Science Institute, 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