Crescent Mimas

A thin sliver of Mimas is illuminated, the long shadows showing off its many craters, indicators of the moon's violent history.

The most famous evidence of a collision on Mimas (246 miles, or 396 kilometers across) is the crater Herschel that gives Mimas its Death Star-like appearance. See PIA12568 for more on Herschel.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 40 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2013.

The view was acquired at a distance of approximately 100,000 miles (200,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 130 degrees. Image scale is 4,000 feet (1 kilometer) per pixel.

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

Quintet of Moons

Five moons pose for the international Cassini spacecraft to create this beautiful portrait with Saturn’s rings.

This view, from 29 July 2011, looks toward the northern, sunlit side of the rings from just above the ringplane.

At the far right, and obscuring Saturn itself, is the planet’s second largest moon Rhea, which spans 1528 km. Rhea is closest to Cassini in this composition, at a distance of 1.1 million kilometers. Its heavily cratered surface bears witness to a violent history, with many craters overlapping or erasing the traces of older impact events.

The nearly 400 km-wide Mimas lies just beyond, and seemingly levitates just above Saturn’s innermost rings. The outline of the moon’s large, distinguishing crater Herschel is partially covered by Rhea, but can just be made out along with numerous smaller craters.

Brightly reflective Enceladus appears above the center of the image and lies beyond the rings, at a distance of 1.8 million kilometers from Cassini. Although not visible in this image, icy Enceladus is covered with a network of frozen ridges and troughs, with plumes of ice particles jetting from fissures in its southern hemisphere.

To the lower left, tiny Pandora, just 81 km across, appears skewered by Saturn’s outer rings – in fact, it orbits between the planet’s A and F rings.

Last but not least, the irregularly shaped Janus lies at the far left of the image, several shadowy surface markings corresponding to large impact craters.

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

Enceladus Creating Saturn's E-Ring

Wispy fingers of bright, icy material reach tens of thousands of kilometers outward from Saturn's moon Enceladus into the E ring, while the moon's active south polar jets continue to fire away.

This astonishing, never-before-seen structure is made visible with the sun almost directly behind the Saturn system from Cassini's vantage point. The sun-Enceladus-spacecraft angle here is 175 degrees, a viewing geometry in which structures made of tiny particles brighten substantially.

These features are very likely the result of particles injected into Saturn orbit by the Enceladus geysers: Those injected in the direction of the moon's orbital motion end up on larger, slower orbits and trail Enceladus in its orbit, and those injected into the opposite direction end up smaller, faster orbits and lead Enceladus. (Orbital motion is counter-clockwise.) In addition, the configuration of wisps may hint at an interaction between Saturn's magnetosphere and the torrent of particles issuing from Enceladus.

In addition to the wisps, another unexpected detail is the dark gore in the center of the ring, following the moon in its orbit, likely brought about by the sweeping action of Enceladus as it orbits in the center of the E ring.

The view looks down onto Enceladus (505 kilometers, or 314 miles across) from about 15 degrees above the ringplane. Tethys (1,071 kilometers, or 665 miles across) is visible to the left of Enceladus.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 15, 2006, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Enceladus. Image scale is 128 kilometers (80 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Note: The above image is one of several used in a recent ESA press release, Herschel Confirms Enceladus as Primary Water Supply for Saturn's Atmosphere. This story is unique in that this is the first instance where a moon is directly affecting the atmosphere of the host planet.

Mimas

The Cassini spacecraft turns the eye of its camera toward Saturn's moon Mimas and spies the large Herschel Crater which itself looks like the iris of an eye peering out into space.

Herschel Crater is 130 kilometers, or 81 miles, wide and covers most of the right of this image. Scientists continue to study this impact basin and its surrounding terrain (see PIA12568).

Lit terrain seen here is on leading hemisphere of Mimas (396 kilometers, or 246 miles across). North on Mimas is up and rotated 1 degree to the left.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 16, 2010. The view was obtained at a distance of approximately 103,000 kilometers (64,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 113 degrees. Image scale is 613 meters (2,011 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Mimas' Blue Streak

This enhanced-color view of Saturn's moon Mimas was made from images obtained by NASA's Cassini spacecraft. It highlights the bluish band around the icy moon's equator. The view shows the hemisphere that faces forward in Mimas' orbit around Saturn. The large round gouge on the surface is Herschel Crater.

This composite image was made by processing raw images obtained by Cassini's imaging cameras from 2004 to 2009. Scientists analyzed frames shot through visible-light, ultraviolet and infrared filters. The processing enhanced our views of these moons beyond what could be seen by the human eye.

The dark, bluish band around Mimas matches patterns one might expect if the surface were being irradiated by high-energy electrons that drift in a direction opposite to the flow of plasma in the magnetic bubble around Saturn. Scientists are still figuring out exactly what is happening, but the electrons appear to be zapping the Mimas surface in a way that matches the Pac-Man thermal pattern detected by Cassini's composite infrared spectrometer early in 2010.

Photo credit: NASA/JPL/SSI/LPI

Note: For a brief technical discussion about how Mimas got its blue streak, see PIA13425: Moons Under Bombardment.

Mimas and Dione

The smaller moon Mimas upstages the larger moon Dione as the dramatic Herschel Crater is spotlighted on Mimas in this Cassini spacecraft view.

Herschel Crater is about 130 kilometers, or 81 miles, wide and covers a significant part of Mimas (396 kilometers, or 246 miles across) at the top of this picture. Smaller craters are visible on Dione (1,123 kilometers, or 698 miles across) in the lower portion of this image.

Because of the particular viewing geometry here, sunlight illuminates the leading hemisphere of Mimas on the left, and light reflected off Saturn dimly lights the Saturn-facing side of Mimas on the right. Lit terrain seen on the left of Dione is on the anti-Saturn side of that moon.

The image was taken in visible red light with the Cassini spacecraft narrow-angle camera on March 23, 2010. The view was obtained at a distance of approximately 1.6 million kilometers (994,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 87 degrees. The view was obtained at a distance of approximately 1.2 million kilometers (746,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 87 degrees. Image scale is 10 kilometers (6 miles) per pixel on Mimas and 7 kilometers (4 miles) per pixel on Dione.

Photo credit: NASA/JPL/Space Science Institute

Herschel Crater on Mimas

Herschel Crater features prominently on the moon Mimas in this Cassini spacecraft image, which gives the impression of an eye staring out into space.

Herschel Crater is about 130 kilometers, or 81 miles, wide and covers a significant part of the moon. This view looks toward the leading hemisphere of Mimas (396 kilometers, or 246 miles across). North on Mimas is up and rotated 1 degree to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 3, 2010. The view was acquired at a distance of approximately 476,000 kilometers (296,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 56 degrees. Image scale is 3 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Note: For an excellent close-up view of Herschel Crater, see this earlier post on one of my other blogs, Ministry of Space Exploration.