Stress at Enceladus

These images, based on ones obtained by NASA's Cassini spacecraft, show how the pull of Saturn's gravity can deform the surface of Saturn's moon Enceladus in the south polar region crisscrossed by fissures known as "tiger stripes." The blue arrows show the different kinds of stress that can occur at the tiger stripes, allowing jets of water vapor and organic particles to spray out. As Enceladus orbits Saturn, Saturn's gravitational forces can cause the fissure to pull apart (middle panel) or cause the two banks to move side-to-side like California's San Andreas Fault. The red stripe shows where gaps open because of motion and would be places where material could erupt. The images here focus on the tiger stripe known as Alexandria Sulcus.

Image credit: NASA/JPL-Caltech/SSI/LPI/GSFC

Note: For more information, see Cassini Sees Saturn Stressing out Enceladus.

Dione in False Colors

This view highlights tectonic faults and craters on Dione, an icy world that has undoubtedly experienced geologic activity since its formation.

To create the enhanced-color view, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. This "color map" was then superposed over a clear-filter image. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

This view looks toward the leading hemisphere on Dione (1,126 kilometers, or 700 miles across). North is up and rotated 20 degrees to the right.

See PIA07690 for a similar monochrome view.

All images were acquired with the Cassini spacecraft narrow-angle camera on December 24, 2005 at a distance of approximately 151,000 kilometers (94,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 99 degrees. Image scale is 896 meters (2,940 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Note: For more information, see Cassini Detects Hint of Fresh Air at Dione.

Southern Enceladus in Radar View

NASA's Cassini spacecraft obtained these views of the south polar area of Saturn's moon Enceladus in visible and near-visible (ultraviolet and infrared) light and synthetic-aperture radar (SAR). The region is south of 45 degrees South latitude. The SAR image, acquired November 6, 2011, is shown as an arc running from upper left to lower right, accented in light blue. Bright and dark edges of this arc are artifacts of the radar imaging process. The background image was taken with visible-light (PIA08342), with color added for emphasis (see below). Visible-light images, like we normally see in photographs, are mostly bright or dark depending on their target's chemical composition, while brightness in SAR images usually depends on how rough or smooth the surface is. The SAR swath is about 15 miles (25 kilometers) wide and is centered at 655 South latitude, 295 West longitude.

The color in the background image is used to separate different materials using ultraviolet, visible and infrared images taken from 2004 to 2009 (see PIA13423). Blue colors represent icy material that originated in the plumes and fell back to the surface. Since these images were taken using illumination by sunlight, they sense ice particles and other roughness in the wavelength range of 50 to 100 microns. The SAR swath uses microwaves 2 centimeters long in wavelength to "light" the surface, so it senses roughness in that range. In addition, the SAR may be seeing that roughness slightly under the surface.

From east-to-west (bottom right to top left), the SAR image crosses near-south-polar terrain close to many of the active sulci, which are long fissures. Throughout the scene, the surface is covered with a network of linear and near-linear grooves and fractures, interpreted to be due to extension, or pulling apart, of Enceladus' crust. These are dominated by a set of larger grooves, about a mile (kilometer) wide, running many tens of miles (kilometers) in length, and smaller grooves about 700 feet (200 meters) wide. A v-shaped region near the lower (eastern) end of the SAR swath, bounded by large faults, appears brighter to radar than most other areas, most likely the result of a rougher surface in the 2-centimeter-wavelength scale. Within, the terrain appears to be slightly more broken up, possibly the result of more dynamic tectonic forces disrupting the surface. The few-miles-wide (few-kilometers-wide) fault bounding the westernmost edge (top) edge of this area looks similar to the four active sulci that run parallel to it, suggesting that it is formed by the same processes; this feature is discussed in PIA15171. A similar fault about 1 to 2 miles (2 to 3 kilometers) wide runs along the center of much of the SAR swath for at least 47 miles (75 kilometers). Farther west still, the swath crosses another v-shaped, SAR-bright region bounded by large faults, including part of the Mosul Sulci system (see PIA15170). Once again, the network of fractures within the bright region appear to be rougher and more broken up. It also coincides with unusually colored terrain surrounding the active sulci (seen in the background images), and so possibly indicates a relatively young or active surface.

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

Note: For other images in this series, see PIA15170: Enceladus Sparkle and PIA15171: Groovy Enceladus.

Geology of Tethys

Geologic faults among craters on Saturn's moon Tethys are depicted in this image captured during a flyby of the moon by NASA's Cassini spacecraft on August 14, 2010.

The brightly illuminated, prominent impact crater near the bottom middle of this image has been dissected by numerous parallel faults that run diagonally across the image. The presence of the faults that cut through the crater and the movement of surface materials have made the crater outline somewhat non-circular. Near the center of the image, running diagonally from the left to right, is an old graben, or linear depression of terrain between faults. See PIA07736 and PIA07734 for images showing geologic features on Tethys taken during an earlier flyby.

Below these faults and near the middle top of the image is a large ancient impact crater that is so highly overprinted by more recent craters that it can barely be recognized.

On the left of the image, there are some horizontal lines that can be seen very faintly cutting across craters. These lines are artifacts of missing data in the raw image that could not be eliminated through processing the image.

This view looks toward the leading hemisphere of Tethys (1062 kilometers, 660 miles across). The view is centered on terrain at 59 degrees North latitude, 79 degrees West longitude.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 40,000 kilometers (25,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 103 degrees. Image scale is 234 meters (767 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute