Angling Saturn

The Cassini spacecraft takes an angled view toward Saturn, showing the southern reaches of the planet with the rings on a dramatic diagonal.

North on Saturn is up and rotated 16 degrees to the left. This view looks toward the southern, unilluminated side of the rings from about 14 degrees below the ringplane. The rings cast wide shadows on the planet's southern hemisphere.

The moon Enceladus (313 miles, or 504 kilometers across) appears as a small, bright speck in the lower left of the image.

The image was taken with the Cassini spacecraft wide-angle camera on June 15, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.8 million miles (2.9 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 72 degrees. Image scale is 11 miles (17 kilometers) 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.

Image credit: NASA/JPL-Caltech/Space Science Institute

Colorful Colossi and Changing Hues

A giant of a moon appears before a giant of a planet undergoing seasonal changes in this natural color view of Titan and Saturn from NASA's Cassini spacecraft.

Titan, Saturn's largest moon, measures 3,200 miles, or 5,150 kilometers, across and is larger than the planet Mercury. Cassini scientists have been watching the moon's south pole since a vortex appeared in its atmosphere in 2012. See PIA14919 and PIA14920 to learn more about this mass of swirling gas around the pole in the atmosphere of the moon.

As the seasons have changed in the Saturnian system, and spring has come to the north and autumn to the south, the azure blue in the northern Saturnian hemisphere that greeted Cassini upon its arrival in 2004 is now fading. The southern hemisphere, in its approach to winter, is taking on a bluish hue. This change is likely due to the reduced intensity of ultraviolet light and the haze it produces in the hemisphere approaching winter, and the increasing intensity of ultraviolet light and haze production in the hemisphere approaching summer. (The presence of the ring shadow in the winter hemisphere enhances this effect.) The reduction of haze and the consequent clearing of the atmosphere makes for a bluish hue: the increased opportunity for direct scattering of sunlight by the molecules in the air makes the sky blue, as on Earth. The presence of methane, which generally absorbs in the red part of the spectrum, in a now clearer atmosphere also enhances the blue.

This view looks toward the northern, sunlit side of the rings from just above the ring plane.

This mosaic combines six images -- two each of red, green and blue spectral filters -- to create this natural color view. The images were obtained with the Cassini spacecraft wide-angle camera on May 6, 2012, at a distance of approximately 483,000 miles (778,000 kilometers) from Titan. Image scale is 29 miles (46 kilometers) per pixel on Titan.

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.

Image Credit: NASA/JPL-Caltech/SSI

NASA'S Cassini Finds Probable Subsurface Ocean on Saturn Moon

Dwayne Brown

Headquarters, Washington

202-358-1726

dwayne.c.brown@nasa.gov

 

Jia-Rui C. Cook

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-0850

jccook@jpl.nasa.gov

WASHINGTON -- Data from NASA's Cassini spacecraft have revealed Saturn's moon Titan likely harbors a layer of liquid water under its ice shell.

Researchers saw a large amount of squeezing and stretching as the moon orbited Saturn. They deduced that if Titan were composed entirely of stiff rock, the gravitational attraction of Saturn would cause bulges, or solid "tides," on the moon only 3 feet (1 meter) in height. Spacecraft data show Saturn creates solid tides approximately 30 feet (10 meters) in height, which suggests Titan is not made entirely of solid rocky material. The finding appears in today's edition of the journal Science.

"Cassini's detection of large tides on Titan leads to the almost inescapable conclusion that there is a hidden ocean at depth," said Luciano Iess, the paper's lead author and a Cassini team member at the Sapienza University of Rome, Italy. "The search for water is an important goal in solar system exploration, and now we've spotted another place where it is abundant."

Titan takes only 16 days to orbit Saturn, and scientists were able to study the moon's shape at different parts of its orbit. Because Titan is not spherical but slightly elongated like a football, its long axis grew when it was closer to Saturn. Eight days later, when Titan was farther from Saturn, it became less elongated and more nearly round. Cassini measured the gravitational effect of that squeeze and pull.

Scientists were not sure Cassini would be able to detect the bulges caused by Saturn's pull on Titan. By studying six close flybys of Titan from Feb. 27, 2006, to Feb. 18, 2011, researchers were able to determine the moon's internal structure by measuring variations in the gravitational pull of Titan using data returned to NASA's Deep Space Network (DSN).

"We were making ultrasensitive measurements, and thankfully Cassini and the DSN were able to maintain a very stable link," said Sami Asmar, a Cassini team member at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "The tides on Titan pulled up by Saturn aren't huge compared to the pull the biggest planet, Jupiter, has on some of its moons. But, short of being able to drill on Titan's surface, the gravity measurements provide the best data we have of Titan's internal structure."

An ocean layer does not have to be huge or deep to create these tides. A liquid layer between the external, deformable shell and a solid mantle would enable Titan to bulge and compress as it orbits Saturn. Because Titan's surface is mostly made of water ice, which is abundant in moons of the outer solar system, scientists infer Titan's ocean is likely mostly liquid water.

On Earth, tides result from the gravitational attraction of the moon and sun pulling on our surface oceans. In the open oceans, those can be as high as two feet (60 centimeters). While water is easier to move, the gravitational pulling by the sun and moon also causes Earth's crust to bulge in solid tides of about 20 inches (50 centimeters).

The presence of a subsurface layer of liquid water at Titan is not itself an indicator for life. Scientists think life is more likely to arise when liquid water is in contact with rock, and these measurements cannot tell whether the ocean bottom is made up of rock or ice. The results have a bigger implication for the mystery of methane replenishment on Titan.

"The presence of a liquid water layer in Titan is important because we want to understand how methane is stored in Titan's interior and how it may outgas to the surface," said Jonathan Lunine, a Cassini team member at Cornell University. "This is important because everything that is unique about Titan derives from the presence of abundant methane, yet the methane in the atmosphere is unstable and will be destroyed on geologically short timescales."

A liquid water ocean, "salted" with ammonia, could produce buoyant ammonia-water liquids that bubble up through the crust and liberate methane from the ice. Such an ocean could serve also as a deep reservoir for storing methane.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate in Washington. DSN, also managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. Cassini's radio science team is based at Wellesley College in Massachusetts.

For more information about the mission, visit http://www.nasa.gov/cassini.

- end -

Serene Scene

Even in a peaceful looking scene such as this one of Saturn and its moon Tethys, the Cassini spacecraft reveals clues about how Saturn is ever-changing. Saturn's northern hemisphere still shows the scars of the huge storm that raged through much of 2011 (see PIA14905). And, day by day, the shadows cast by the rings on the planet's southern hemisphere are growing wider as the seasons progress toward northern summer. See PIA11667 and PIA09793 to learn about the changing seasons and the shadows cast by the rings.

Tethys (660 miles, or 1,062 kilometers across) appears above the rings to the left of the center of the image.

The image was taken with the Cassini spacecraft wide-angle camera on Jan. 10, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 39 degrees. Image scale on Saturn is 84 miles (136 kilometers) per pixel.

Image Credit: NASA/JPL-Caltech/Space Science Institute

Saturn's Brightly Reflective Moon Enceladus

A brightly reflective Enceladus appears before Saturn's rings, while the planet's larger moon Titan looms in the distance.

Jets of water ice and vapor emanating from the south pole of Enceladus, which hint at subsurface sea rich in organics, and liquid hydrocarbons ponding on the surface on the surface of Titan make these two of the most fascinating moons in the Saturnian system.

Enceladus (313 miles, or 504 kilometers across) is in the center of the image. Titan (3,200 miles, or 5,150 kilometers across) glows faintly in the background beyond the rings. This view looks toward the anti-Saturn side of Enceladus and the Saturn-facing side of Titan. The northern, sunlit side of the rings is seen from just above the ringplane.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on March 12, 2012. The view was acquired at a distance of approximately 600,000 miles (1 million kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 36 degrees. Image scale is 4 miles (6 kilometers) per pixel on Enceladus.

Image credit: NASA/JPL-Caltech/Space Science Institute

Cassini Spacecraft Sees New Objects Blazing Trails in Saturn Ring

Dwayne Brown

Headquarters, Washington

202-358-1726

dwayne.c.brown@nasa.gov

 

Jia-Rui C. Cook

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-0850

jccook@jpl.nasa.gov

WASHINGTON -- Scientists working with images from NASA's Cassini spacecraft have discovered strange, half-mile-sized objects punching through one of Saturn's rings and leaving glittering trails behind them. The results will be presented tomorrow at the European Geosciences Union meeting in Vienna, Austria.

The penetration occurred in the outermost of Saturn's main rings, called the F ring, which has a circumference of 550,000 miles (881,000 kilometers). Scientists are calling the trails in the F ring "mini-jets." Cassini scientists combed through 20,000 images and found 500 examples of these rogues during the seven years Cassini has been at Saturn.

"Beyond just showing us the strange beauty of the F ring, Cassini's studies of this ring help us understand the activity that occurs when solar systems evolve out of dusty disks that are similar to, but obviously much grander than, the disk we see around Saturn," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

Scientists have known relatively large objects can create channels, ripples and snowballs, or clumps of icy material, in the F ring. However, scientists did not know what happened to these snowballs after they were created. Some were broken up by collisions or tidal forces in their orbit around Saturn. Scientists now have evidence some of the smaller ones survived, and their differing orbits mean they go on to strike through the F ring on their own.

"I think the F ring is Saturn's weirdest ring, and these latest Cassini results go to show how the F ring is even more dynamic than we ever thought," said Carl Murray, a Cassini imaging team member based at Queen Mary University of London, U.K. "These findings show us that the F ring region is like a bustling zoo of objects from a half-mile (0.8-kilometer) in size to moons like Prometheus a hundred miles (160.9 kilometers) in size, creating a spectacular show."

These small objects appear to collide with the F ring at gentle speeds about 4 mph (2 meters per second). The collisions drag glittering ice particles out of the F ring with them, leaving a trail of 20-110 miles (40-180 kilometers) long.

In some cases, the objects traveled in packs, creating mini-jets that looked exotic, like the barb of a harpoon. Other new images show grand views of the entire F ring and the swirls and eddies from the different kinds of objects moving through and around it.

Saturn's rings are comprised primarily of water ice. The chunks of ice that make up the main rings spread out 85,000 miles (140,000 kilometers) from the center of Saturn. Scientists believe the rings' average thickness is approximately 30 feet (10 meters).

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington. The imaging team is based at the Space Science Institute in Boulder, Colo.

New images and movies of the mini-jets are available at http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20120423.html.

For information about Cassini, visit http://www.nasa.gov/cassini.

- end -