Rocks/Ice sheets/Enceladus

This is an enhanced color view of Enceladus. Credit: NASA/JPL/Space Science Institute.

"The mosaic was created from 21 false-color frames taken during the Cassini spacecraft's close approaches to Enceladus on March 9 and July 14, 2005. Images taken using filters sensitive to ultraviolet, visible and infrared light (spanning wavelengths from 338 to 930 nanometers) were combined to create the individual frames."

"The mosaic is an orthographic projection centered at 46.8 degrees south latitude, 188 degrees west longitude, and has an image scale of 67 meters (220 feet) per pixel. The original images ranged in resolution from 67 meters per pixel to 350 meters (1,150 feet) per pixel and were taken at distances ranging from 11,100 to 61,300 kilometers (6,900 to miles) from Enceladus."

Astronomy

These images are the trailing and leading hemispheres of Enceladus from left to right. Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute.

These are the north and south polar hemispheres of Enceladus from left to right. Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute.

"This set of global, color mosaics of Saturn's moon Enceladus was produced from images taken by NASA's Cassini spacecraft during its first ten years exploring the Saturn system. These are the first global color maps of these moons produced from the Cassini data."

"The yellowish and magenta tones in the map are believed to be due to differences in the thickness of surface deposits there. In addition, many of the most recently formed fractures on Enceladus have a stronger ultraviolet signature (meaning they are brighter), and they appear bluish in these maps. The famous "tiger stripe" fractures, which are the sources of the plumes venting gas and dust into space have a similar color. Researchers think this color could be due to large-grained ice exposed on the surface. Other subtle color markings are related to the moon's local and regional geologic history."

"The colors shown in these global mosaics are enhanced, or broader, relative to human vision, extending into the ultraviolet and infrared range."

"Resolution on Enceladus in the maps is 100 meters per pixel."

"Image selection, radiometric calibration, geographic registration and photometric correction, as well as mosaic selection and assembly [have been performed]."

Geophysics

Main article: Geophysics

File:Saturn lit side.jpg

Enceladus lit both by sunshine and Saturnshine. Credit: NASA/Cassini.

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This is an Enceladus tiger stripe from Cassini. Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA.

"The south polar terrain is marked by a striking set of 'blue' fractures and encircled by a conspicuous and continuous chain of folds and ridges, testament to the forces within Enceladus that have yet to be silenced."

The image on the right shows both sunlit and Saturnlit Enceladus.

The second image down on the right is an Enceladus tiger stripe close up.

"Previously, the tiger stripe regions were found to be expelling plumes of water-ice, fueling speculation that liquid seas might occur beneath Enceladus' frozen exterior. Such seas are so interesting because they are candidates to contain extraterrestrial life. Important processes in tiger stripe formation may include heating from below and moonquakes. Visible above is terrain on Enceladus so young that only a few craters are visible. This newly released raw image shows at least one type of false artifact, however, as seeming chains of craters are not so evident in other concurrently released images of the same region. The large tiger stripe across the image middle is impressive not only for its length and breadth, but because a large internal shadow makes it also appear quite deep."

Nearby, this Enceladus tiger stripe, or large canyon, are catenae or geyser remnants shown in the second photo down on the right.

True polar wanders

Saturn's moon Enceladus may have tipped over. Credit: NASA/JPL-Caltech/Space Science Institute/Cornell University.{{free media}}

"Working with image data from NASA's Cassini mission, researchers have found evidence that Saturn's moon Enceladus may have tipped over, reorienting itself so that terrain closer to its original equator was relocated to the poles. This phenomenon is known as true polar wander."

"Researchers discovered a chain of basins across the surface of Enceladus along with a pair of depressions that line up with an equator and poles, respectively, if the moon's axis of rotation was reoriented by about 55 degrees of latitude."

"These maps look toward the icy moon's southern hemisphere, with colors representing highs and lows. Purple represents the lowest elevations, while red represents the highest."

"The map at left shows the surface of Enceladus in its possible ancient orientation, millions of years ago. The chain of basins representing topographic lows can be seen in blue and purple, running along the equator, with an additional low region around the original south pole. The region that encloses the moon's currently active south polar terrain, with its long, linear "tiger stripe" fractures, would have been at middle latitudes just south of the equator. The map at right shows the current orientation of Enceladus."

Theoretical Enceladus

Def. a satellite of Saturn, the eighth major closest to the planet is called Enceladus.

Visuals

Main articles: Radiation astronomy/Visuals and Visuals

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on November 6, 2011. Credit: NASA/JPL-Caltech/Space Science Institute Cassini.

At right is Saturn's natural satellite, the rocky object, Enceladus.

Enceladus, a moon of Saturn, has one of the highest known albedos of any body in the Solar system, with 99% of EM radiation reflected.

"The Cassini spacecraft looks at a brightly illuminated Enceladus and examines the surface of the leading hemisphere of this Saturnian moon."

"North on Enceladus (313 miles across, or 504 kilometers) is up and rotated 21 degrees to the right."

"The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 6, 2011. The view was obtained at a distance of approximately 67,700 miles (109,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 21 degrees. Image scale is 2,130 feet (649 meters) per pixel."

Greens

Main articles: Radiation astronomy/Greens and Green astronomy

This false-color, close-up look at Saturn's moon Enceladus yields new insight into the different processes that have shaped the moon's icy surface. Credit: NASA/JPL/Space Science Institute.

"This false-color, close-up look at Saturn's moon Enceladus yields new insight into the different processes that have shaped the moon's icy surface."

"Extending through the center of this image is a system of rifts 3 kilometers wide (2 mile) and lanes of grooved terrain 20 kilometers wide (12 mile), which separate two distinct geological provinces. To the right of the boundary is older, cratered terrain - a region peppered with craters ranging from 10 kilometers (6 miles) in diameter, down craters near the limit of resolution. The region is believed to be old because it has accumulated a relatively high density of impact craters over time and the topography is soft and muted, suggesting that it is covered by a layer of particulate materials. The cratered terrain is cut crosswise by numerous faults and fractures ranging in width from hundreds of meters to a few kilometers."

"On the left side of the scene are grooved, icy plains. This broad, relatively flat region is scored by an extensive band of parallel grooves that appear to subdivide the surface into narrow lanes approximately 1 kilometer or half a mile wide. The low abundance of impact craters and crisp relief on topographic features here imply that this region is geologically much younger than the cratered terrain at the right."

"This view is a composite of images taken using filters sensitive to ultraviolet (centered at 338 nanometers), green (centered at 568 nanometers), and near-infrared (centered at 930 nanometers) light, and has been processed to accentuate subtle color differences."

"The uppermost surface of these terrains has a relatively uniform pinkish cast in this picture, suggesting that it is covered with materials of homogeneous composition and grain size. However, many of the fractures reveal a distinctly different color (represented by greenish tones in this false-color image) than the typical surface materials in this region. The fractures seem to penetrate down to a material that is texturally or compositionally different than most surface materials. One possibility is that the walls of the fractures expose outcrops of solid ice or ice with different grain-sizes compared to powdery surface materials that mantle flat-lying surfaces. It is also possible that the color identifies some compositional difference between buried ice and ice at the surface."

"The scene is located on the side of Enceladus that faces away from Saturn. The images were obtained with the Cassini spacecraft narrow-angle camera when the spacecraft was at a distance of approximately 25,700 kilometers (15,969 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 46 degrees. Resolution in the image is about 150 meters (490 feet) per pixel."

The area of the image is at approximately between 0-20°N 135°E on the trailing hemisphere.

Oranges

Main articles: Radiation astronomy/Oranges and Orange astronomy

This color Voyager 2 image mosaic shows the water-ice-covered surface of Enceladus, one of Saturn's icy moons. Credit: NASA/JPL/USGS.

"This color Voyager 2 image mosaic shows the water-ice-covered surface of Enceladus, one of Saturn's icy moons. Enceladus' diameter of just 500 km would fit across the state of Arizona, yet despite its small size Enceladus exhibits one of the most interesting surfaces of all the icy satellites. Enceladus reflects about 90% of the incident sunlight (about like fresh-fallen snow), placing it among the most reflective objects in the Solar System. Several geologic terrains have superposed crater densities that span a factor of at least 500, thereby indicating huge differences in the ages of these terrains. It is possible that the high reflectivity of Enceladus' surface results from continuous deposition of icy particles from Saturn's E-ring, which in fact may originate from icy volcanoes on Enceladus' surface. Some terrains are dominated by sinuous mountain ridges from 1 to 2 km high (3300 to 6600 feet), whereas other terrains are scarred by linear cracks, some of which show evidence for possible sideways fault motion such as that of California's infamous San Andreas fault. Some terrains appear to have formed by separation of icy plates along cracks, and other terrains are exceedingly smooth at the resolution of this image. The implication carried by Enceladus' surface is that this tiny ice ball has been geologically active and perhaps partially liquid in its interior for much of its history. The heat engine that powers geologic activity here is thought to be elastic deformation caused by tides induced by Enceladus' orbital motion around Saturn and the motion of another moon, Dione."

Infrareds

Main articles: Radiation astronomy/Infrareds and Infrared astronomy

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These are temperature maps for Enceladus. Credit:NASA/Cassini.

The images on the right show a predicted thermal, or temperature, map for Enceladus in the left frame. The image in the right frame is an actual thermal scan from Cassini.

Chemicals

Main article: Chemicals

The lower panel is a mass spectrum that shows the chemical constituents sampled in Enceladus' plume. Credit: NASA/JPL/SwRI.{{free media}}

"The lower panel is a mass spectrum that shows the chemical constituents sampled in Enceladus' plume by Cassini's Ion and Neutral Mass Spectrometer during its fly-through of the plume on Mar. 12, 2008. Shown are the amounts, in atomic mass per elementary charge (Daltons [Da]), of water vapor, methane, carbon monoxide, carbon dioxide, simple organics and complex organics identified in the plume."

"The Ion and Neutral Mass Spectrometer was designed and built at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, and the team is at Southwest Research Institute (SwRI) in San Antonio, Texas."

Hypotheses

Main article: Hypotheses

1. Enceladus has an ice sheet covering its entire surface.

See also

• Enceladus
• Ices
• Ice sheets
• Saturn
• Volcanoes/Enceladus

References

External links

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