Enceladus

Enceladus's unusual plume is only easily visible when the Cassini spacecraft and the Sun are on opposite sides of Enceladus. So what's lighting up the moon then? It's light reflected off Saturn. This lighting trick allows the Cassini spacecraft to capture both the back-lit plume and the surface of Enceladus in one shot.

This view looks toward the Saturn-facing hemisphere of Enceladus. North on Enceladus is up. The image was taken in blue light with the Cassini spacecraft narrow-angle camera on April 2, 2013.

The view was acquired at a distance of approximately 517,000 miles (832,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 175 degrees. Image scale is 3 miles (5 kilometers) per pixel.

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

F-Ring Mini-Jet

A beautiful "mini-jet" appears in the dynamic F ring of Saturn. Saturn's A ring (including the Keeler gap and just a hint of the Encke gap at the upper-right) also appears.

The mini-jets are thought by imaging scientists to be caused by low-speed collisions in the F ring ejecting dusty material from the ring's core. For more on the mini-jets, see PIA15504.

This view looks toward the unilluminated side of the rings from about 48 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 20, 2013.

The view was obtained at a distance of approximately 841,000 miles (1.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 82 degrees. Image scale is 5 miles (8 kilometers) per pixel.

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

Saturn's Rings

Saturn's rings appear to form a majestic arc over the planet in this image from the Cassini spacecraft.

This view looks toward the sunlit side of the rings from about 17 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on June 15, 2013 using a spectral filter sensitive to wavelengths of near-infrared light centered at 705 nanometers.

The view was acquired at a distance of approximately 657,000 miles (1.1 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 2 degrees. Image scale is 37 miles (60 kilometers) per pixel.

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

Saturn

The huge storm churning through the atmosphere in Saturn's northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA's Cassini spacecraft. This storm is the largest, most intense storm observed on Saturn and is still active today. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

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

Saturn's Northern Hemisphere Storm in Visual and Infrared

This set of images from NASA's Cassini mission shows the turbulent power of a monster Saturn storm. The visible-light image in the back, obtained on February 25, 2011, by Cassini's imaging camera, shows the turbulent clouds churning across the face of Saturn. The inset infrared image, obtained a day earlier, by Cassini's visual and infrared mapping spectrometer, shows the dredging up of water and ammonia ices from deep in Saturn's atmosphere. This was the first time water ice was detected in Saturn's atmosphere. The storm, first detected by Cassini's radio and plasma wave subsystem in December 2011, churned around the planet in a band around 33 degrees north.

The visible-light image can be seen separately at PIA12826.

Image credit: NASA/JPL-Caltech/SSI/University of Arizona/University of Wisconsin

Note: For more information, see Cassini Sees Saturn Storm's Explosive Power.

Dione

Like their semi-divine namesakes, Dione's twin craters Romulus and Remus (just above-right of center) stand together. Dido, the larger crater featuring a central peak, lies just to the southeast on the day/night terminator.

Lit terrain seen here is on the Saturn-facing hemisphere of Dione. North on Dione is up. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 28, 2013.

The view was obtained at a distance of approximately 870,000 miles (1.4 million kilometers) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 77 degrees. Image scale is 5 miles (8 kilometers) per pixel in the original image. This image has been zoomed in by a factor of 1.5 to enhance clarity.

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

Cassini Data: Titan May Have a Rigid Ice Shell

An analysis of gravity and topography data from the Saturnian moon Titan obtained by NASA's Cassini spacecraft suggests there could be something unexpected about the moon's outer ice shell. The findings, published on August 28 in the journal Nature, suggest that Titan's ice shell could be rigid, and that relatively small topographic features on the surface could be associated with large ice "roots" extending into the underlying ocean.

The study was led by planetary scientists Douglas Hemingway and Francis Nimmo at the University of California, Santa Cruz, who used data from Cassini. The researchers were surprised to find a counter-intuitive relationship between gravity and topography.

"Normally, if you fly over a mountain, you expect to see an increase in gravity due to the extra mass of the mountain," said Nimmo, a Cassini participating scientist. "On Titan, when you fly over a mountain, the gravity gets lower. That's a very odd observation."

One potential explanation is that each bump in the topography on the surface of Titan is offset by a deeper "root" that is big enough to overwhelm the gravitational effect of the bump on the surface. The root could act like an iceberg extending below the ice shell into the ocean underneath it. In this model, Cassini would detect less gravity wherever there is a big chunk of ice rather than water because ice is less dense than water.

"It's like a big beach ball under the ice sheet pushing up on it, and the only way to keep it submerged is if the ice sheet is strong," said Hemingway, the paper's lead author and a Cassini team associate. "If large roots under the ice shell are the explanation, this means that Titan's ice shell must have a very thick rigid layer."

If these findings are correct, a thick rigid ice shell makes it very difficult to have ice volcanoes, which some scientists have proposed to explain other features seen on the surface. They also suggest that convection or plate tectonics are not recycling Titan's ice shell, as they do with Earth's geologically active crust.

Video credit: ESA/NASA/JPL/University of Arizona

Titan's North Polar Collar

Titan's polar collar -- previously seen by Voyager 2 and the Hubble Space Telescope -- has now been observed by the Cassini spacecraft, seen here in ultraviolet light. The collar is believed to be seasonal in nature. Researchers are still studying its cause and evolution.

This view looks toward the Saturn-facing hemisphere of Titan. North on Titan is up and rotated 32 degrees to the right. The image was taken with the Cassini spacecraft narrow-angle camera on April 13, 2013 using a spectral filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers.

The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 4 degrees. Image scale is 7 miles (11 kilometers) per pixel.

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

Earhart Propeller in the A-Ring

Cassini scientists continue their quest to understand the origin and evolution of the newly discovered features observed in Saturn's A-ring which have become known as "propellers." In this image, the propeller which scientists have dubbed "Earhart" (at the lower left of the image) has been re-acquired.

Scientists hope to understand how the bodies which generate the features -- themselves too small to be seen, yet significantly larger than a typical ring particle -- move around the ring over time. It is hoped that these features may provide insights about how forming planets move around their solar systems. For more on Earhart, see PIA12790.

This view looks toward the sunlit side of the rings from about 48 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 11, 2013.

The view was acquired at a distance of approximately 250,000 miles (400,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 99 degrees. Image scale is 1 mile (2 kilometers) per pixel.

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

Abisme Crater

From the USGS Astrogeology Science Center:

The IAU Working Group for Planetary System Nomenclature has approved the name Abisme for a crater on Iapetus. For more information, see the map of Iapetus in the Gazetteer of Planetary Nomenclature.