Thursday, December 29, 2011

Titan and Saturn


The colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft.

The north polar hood can be seen on Titan (3,200 miles or 5,150 kilometers across) and appears as a detached layer at the top of the moon here. See PIA08137 and PIA09739 to learn more about Titan's atmosphere and the north polar hood.

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

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained with the Cassini spacecraft narrow-angle camera on May 21, 2011, at a distance of approximately 1.4 million miles (2.3 million kilometers) from Titan. Image scale is 9 miles (14 kilometers) per pixel on Titan.

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

Wednesday, December 28, 2011

Titan and Dione


Saturn's third-largest moon, Dione, can be seen through the haze of the planet's largest moon, Titan, in this view of the two posing before the planet and its rings from NASA's Cassini spacecraft.

The north polar hood can be seen on Titan appearing as a detached layer at the top of the moon here. See PIA08137 and PIA09739 to learn more about Titan's atmosphere and the north polar hood.

See PIA10560 and PIA07638 to learn more about and see a closer view of the wisps on Dione's trailing hemisphere, which appear as bright streaks here.

This view looks toward the sides of Titan (3,200 miles or 5,150 kilometers across) and Dione (698 miles or 1,123 kilometers across) facing away from Saturn. North is up on the moons. This view looks toward the northern, sunlit side of the rings from just above the ring plane.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained with the Cassini spacecraft narrow-angle camera on May 21, 2011, at a distance of approximately 1.4 million miles (2.3 million kilometers) from Titan and 2 million miles (3.2 million kilometers) from Dione. Image scale is 9 miles (14 kilometers) per pixel on Titan and 12 miles (19 kilometers) on Dione.

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

Tuesday, December 27, 2011

Enceladus


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

See PIA11685 to learn more about the surface of Enceladus. See PIA11688 to learn about the jets of water ice emanating from the moon's south polar region. 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 November 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.

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

Monday, December 26, 2011

Titan and Tethys


Saturn's moon Tethys, with its stark white icy surface, peeps out from behind the larger, hazy, colorful Titan in this view of the two moons obtained by NASA's Cassini spacecraft. Saturn's rings lie between the two.

The north polar hood can be seen on Titan appearing as a detached layer at the top of the moon here. See PIA08137 and PIA09739 to learn more about Titan's atmosphere and the north polar hood.

Ithaca Chasma, a long series of scarps or cliffs on Tethys, can be seen faintly running north-south on that moon. See PIA10460 to learn more.

This view looks toward the side of Titan (3,200 miles or 5,150 kilometers across) facing away from Saturn and the side of Tethys (660 miles or 1,062 kilometers across) facing Saturn. This view looks toward the northern, sunlit side of the rings from just above the ring plane.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired with the Cassini spacecraft narrow-angle camera on May 21, 2011, at a distance of approximately 1.4 million miles (2.3 million kilometers) from Titan and 2.4 million miles (3.8 million kilometers) from Tethys. Image scale is 9 miles (14 kilometers) per pixel on Titan and 18 miles (27 kilometers) per pixel on Tethys.

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

Sunday, December 25, 2011

Titan and Dione in Natural Colors


Saturn's largest moon, Titan, appears deceptively small paired here with Dione, Saturn's third-largest moon, in this view from NASA's Cassini spacecraft.

Titan (3,200 miles or 5,150 kilometers across) is much farther from the spacecraft than Dione (698 miles or 1,123 kilometers across) is in this view. The view was captured at a distance of approximately 684,000 miles (1.1 million kilometers) from Titan but only about 85,000 miles (136,000 kilometers) from Dione.

Titan appears in true color but has been brightened by a factor of about 1.6 relative to Dione. This view looks toward the Saturn-facing side of Titan and the area between the Saturn-facing side and leading hemisphere of Dione. North is up on the moons.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained with the Cassini spacecraft wide-angle camera on November 6, 2011. Scale in the original image was 5 miles (8 kilometers) per pixel on Dione and 41 miles (66 kilometers) per pixel on Titan. The image has been magnified by a factor of 1.5 and contrast-enhanced to aid visibility.

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

Saturday, December 24, 2011

Titan


These views from NASA's Cassini spacecraft look toward the south polar region of Saturn's largest moon, Titan, and show a depression within the moon's orange and blue haze layers near the south pole.

The close-up view was captured with the narrow-angle camera. Another view taken a second later with the wide-angle camera is also included here for context.

The moon's high altitude haze layer appears blue here whereas the main atmospheric haze is orange. The difference in color could be due to particle size of the haze. The blue haze likely consists of smaller particles than the orange haze.

The depressed or attenuated layer appears in the transition area between the orange and blue hazes about a third of the way in from the left edge of the narrow-angle image. The moon's south pole is in the upper right of this image. This view suggests Titan's north polar vortex, or hood, is beginning to flip from north to south. See PIA08137 to learn about Titan's north polar hood. To learn about changes since Saturn's August 2009 equinox, see PIA11603 and PIA11667.

The southern pole of Titan is going into darkness as the Sun advances towards the north with each passing day. The upper layer of Titan's hazes is still illuminated by sunlight.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained on September 11, 2011 at a distance of approximately 83,000 miles (134,000 kilometers) from Titan. Image scale is 2,581 feet (787 meters) per pixel.

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

Thursday, December 22, 2011

Dione


NASA's Cassini spacecraft obtained this unprocessed image on December 12, 2011. The camera was pointing toward Saturn's moon Dione from approximately 76,344 miles (122,864 kilometers) away.

Photo credit: NASA/JPL/Space Science Institute

Wednesday, December 21, 2011

Enceladus and Epimetheus by Saturn's Terminator


A pair of Saturn's moons appear insignificant compared to the immensity of the planet in this Cassini spacecraft view along the terminator where day transitions to night.

The larger moon Enceladus (313 miles, or 504 kilometers across) is also on the left, just a bit closer to the center of the image. Epimetheus (70 miles, or 113 kilometers across) appears as a tiny black speck on the far left of the image, left of Enceladus, just below the thin line of the rings. The rings cast wide shadows on the southern hemisphere of the planet.

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

The image was taken with the Cassini spacecraft wide-angle camera on November 4, 2011 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 746,000 miles (1.2 million kilometers) from Saturn and roughly 600,000 miles (1 million kilometers) from Enceladus and Epimetheus. Image scale is about 47 miles (75 kilometers) per pixel on Saturn, 37 miles (60 kilometers) per pixel on Enceladus and 41 miles (66 kilometers) per pixel Epimetheus.

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

Tuesday, December 20, 2011

Dione


NASA's Cassini spacecraft obtained this unprocessed image on December 12, 2011. The camera was pointing toward Saturn's moon Dione from approximately 69,989 miles (112,636 kilometers) away.

Photo credit: NASA/JPL/Space Science Institute

Note: I'm sorry to say, I don't know off-hand what the other two moons in this picture are.

Tuesday, December 13, 2011

Dione


The Cassini spacecraft examines the anti-Saturnian side of Dione and shows the cratered surface east of the moon's distinctive wispy terrain.

The wispy terrain, which consists of bright cliffs on the moon's trailing hemisphere, can just barely be seen on the limb of the moon on the left of the image. North on Dione (698 miles, or 1,123 kilometers across) is up. See PIA12608 for a better view of the wisps. See PIA07769 for more southern view of Dione presented in dramatic false colors.

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

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 2, 2011. The view was obtained at a distance of approximately 174,000 miles (280,000 kilometers) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 11 degrees. Image scale is 2 miles (3 kilometers) per pixel.

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

Wednesday, December 7, 2011

Mimas, Prometheus and the Rings


Saturn's rings lie between a pair of moons in this Cassini spacecraft view that features Mimas and Prometheus.

Mimas (246 miles or 396 kilometers across) is the more noticeable of the two moons and is in the top left of the view. The smaller moon Prometheus (53 miles, or 86 kilometers across) is near the center of the image and is closest to Cassini. Mimas is beyond the rings and farthest from the spacecraft.

Lit terrain seen on Mimas is on the leading hemisphere of the moon. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on November 4, 2011. The view was acquired at a distance of approximately 746,000 miles (1.2 million kilometers) from Prometheus and 870,000 miles (1.4 million kilometers) from Mimas. Image scale is 4 miles (7 kilometers) per pixel on Prometheus and 5 miles (8 kilometers) per pixel on Mimas.

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

Saturday, December 3, 2011

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.

Wednesday, November 30, 2011

Kraken Mare


The Cassini spacecraft looks toward Saturn's largest moon, Titan, and spies the huge Kraken Mare in the moon's north.

Kraken Mare, a large sea of liquid hydrocarbons, is visible as a dark area near the top of the image. See PIA12811 and PIA11626 to learn more.

This view looks toward the Saturn-facing side of Titan (3,200 miles across, or 5,150 kilometers,). North on Titan is up and rotated 29 degrees to the left.

The image was taken with the Cassini spacecraft narrow-angle camera on September 14, 2011 using a spectral filter sensitive to wavelengths of near-infrared light centered at 938 nanometers. The view was acquired at a distance of approximately 1.2 million miles (1.9 million kilometers) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 26 degrees. Image scale is 7 miles (12 kilometers) per pixel.

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

Tuesday, November 22, 2011

Hyperion


The Cassini spacecraft looks at Saturn's highly irregular moon Hyperion in this view from the spacecraft's flyby of the moon on August 25, 2011.

Hyperion (168 miles, or 270 kilometers across) has an irregular shape, and it tumbles through its orbit: that is, it does not spin at a constant rate or in a constant orientation. (A standard reference latitude-longitude system has not yet been devised for this moon.) Images such as this one extend previous coverage and allow a better inventory of the surface features, the satellite's shape and changes in its spin.

See PIA06243 and PIA07761 to learn more and to watch a movie.

The image was taken with the Cassini spacecraft narrow-angle camera using a combination of spectral filters sensitive to wavelengths of polarized green light centered at 617 and 568 nanometers. The view was obtained at a distance of approximately 36,000 miles (58,000 kilometers) from Hyperion and at a Sun-Hyperion-spacecraft, or phase, angle of 43 degrees. Image scale is 1,145 feet (349 meters) per pixel.

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

Monday, November 21, 2011

Close-Up of Saturn's Northern Hemisphere Storm


The biggest, most long-lasting Saturnian storm seen by either NASA's Cassini or Voyager spacecraft roils the atmosphere of the gas giant in this nearly true-color mosaic of Cassini images.

See PIA14903 and PIA14905 to learn more about the size and development of this storm. This mosaic shows the storm's effects encircling the planet and was created using 126 images taken in succession as different parts of Saturn's northern hemisphere rotated into Cassini's view.

Images taken using red, green and blue spectral filters are usually combined to create a natural color view. Because visible red light images were not available, images taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers were used in place of red. So the color is close to natural color, but is not exact.

A second version of this mosaic is also included here (Figure 1). This view uses these same nearly true color filters, but the images were contrast enhanced. The result is a view that increases the visibility of features.

The head of the storm is near the center of the mosaic, and a train of vortices appears as blue spots just to the south of the head. These blue spots are parts of the storm's tail that have already encircled the planet and are approaching from the west (left in the image). The blue color indicates they have some high, semi-transparent haze but no thick clouds underneath because there are no white- or yellow-colored clouds shown here.

This mosaic covers an area ranging from about 18 degrees north latitude to 47 degrees north latitude. The views stretch the whole longitude range, passing through 360/0 degrees west longitude near the far right of the mosaics.

The images were obtained with the Cassini spacecraft narrow-angle camera on March 6, 2011, over about 11 hours (about a Saturnian day) at a distance of approximately 2 million miles (3.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 83 degrees. These mosaics are simple cylindrical map projections, defined such that a square pixel subtends equal intervals of latitude and longitude. At higher latitudes, the pixel size in the north-south direction remains the same, but the pixel size (in terms of physical extent on the planet) in the east-west direction becomes smaller. The pixel size is set at the equator, where the distances along the sides are equal. This map has a pixel size of 28 miles (45 kilometers) at the equator.

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

Sunday, November 20, 2011

Chronicling Saturn's Northern Storm


This series of images from NASA's Cassini spacecraft shows the development of the largest storm seen on the planet since 1990. These true-color and composite near-true-color views chronicle the storm from its start in late 2010 through mid-2011, showing how the distinct head of the storm quickly grew large but eventually became engulfed by the storm's tail.

The earliest image of the storm, taken December 5, 2010, is in the top left of the panel. The storm appears only as a small, white cloud on the terminator between the day side and night side of the planet. See PIA14905 for a magnified view of the storm at this time.

The next view, in the top middle of the panel and taken January 2, 2011, shows that the head quickly grew much larger and a tail began to trail a great distance eastward. Some of the clouds moved south and got caught up in a current that flows to the east (to the right) relative to the storm head. In the top right of the panel, this tail, which appears as slightly blue clouds south and now west (left) of the storm head, can be seen encountering the storm in the February 25 image.

The April 22 image, in the bottom left of the panel, is one of Cassini's last views of the storm when it still had a recognizable head. In this view, the tail is south of the head and is well established by this time.

The May 18 view, in the bottom middle, shows only the storm's tail. The head still existed at this time, but it is beyond the horizon and out of the field of view here.

Between the time of the May 18 image and the next image shown here (from August 12), the head of the storm was engulfed by the part of the storm's tail that spread eastward at the same latitude as the head. The August 12 image, in the bottom right, shows that the head has lost its distinct identity and is now just part of the jumble of the storm.

Also visible in these images are several of Saturn's moons and the shadows cast onto the planet by moons. For example, the planet's second largest moon, Rhea, can be seen in the February 25 view.

The February 25 and August 12 views are true color. Images taken using red, green and blue spectral filters were combined to create these natural-color views.

The December 5, January 2, April 22 and May 18 views are nearly true color. Because a visible red light image was not available, an image taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers was used in place of red. So the color is close to natural color, but it is not exact.

These views were acquired at distances ranges from approximately 1.4 million miles (2.2 million kilometers) to 1.9 million miles (3.0 million kilometers) from Saturn and at Sun-Saturn-spacecraft, or phase, angles of 41 degrees to 99 degrees. All the views are set to a scale of 101 miles (162 kilometers) per pixel.

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

Note: For other pictures in this series, see PIA14901: Eleven Hours Later and PIA14902: Birth of a Behemoth Storm.

Saturday, November 19, 2011

Saturn's Northern Hemisphere Storm


Saturn's northern storm marches through the planet's atmosphere in the top right of this false-color mosaic from NASA's Cassini spacecraft.

See PIA14905 to learn more about this storm and watch its development over several months. Earlier in the Cassini mission, the spacecraft chronicled a smaller storm in the southern hemisphere, called the "Dragon Storm." See PIA06197 to learn more about that storm and to see a similar, false-color view.

Saturn's atmosphere and its rings are shown here in a false-color composite made from 12 images taken in near-infrared light through filters that are sensitive to varying degrees of methane absorption. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable along the top edge of the view, indicate intermediate clouds. White and blue indicate high clouds and haze. The rings appear as a thin horizontal line of bright blue because they are outside of the atmosphere and not affected by methane absorption.

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

The images were taken with the Cassini spacecraft wide-angle camera using a combination of spectral filters sensitive to wavelengths of near-infrared light. The images filtered at 890 nanometers are projected as blue. The images filtered at 728 nanometers are projected as green, and images filtered at 752 nanometers are projected as red.

The images were taken on January 11, 2011, over about 50 minutes, at a distance of approximately 569,000 miles (915,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 45 degrees. The images were re-projected to the same viewing geometry, so that scale in this final mosaic is 63 miles (102 kilometers) per pixel.

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

Note: For similar images, see PIA12828: Storm Head in False Color and PIA12829: Storm Tail in False Color.

Tuesday, November 15, 2011

Enceladus and Epimetheus


During a flyby of Saturn's moon Enceladus on October 1, 2011, the Cassini spacecraft snapped this portrait of the moon joined by its sibling Epimetheus and the planet's rings.

Enceladus (313 miles, or 504 kilometers across) takes up the center of the image, and its famous south polar jets can faintly be seen at the bottom of the image. See PIA11688 to learn more about those jets.

Epimetheus (70 miles, or 113 kilometers across) peeps into view from beyond the northern reaches of Enceladus. Lit terrain seen on Enceladus is in the area between the leading hemisphere and anti-Saturn side of the moon. North is up. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

Enceladus and Epimetheus have been contrast enhanced and brightened by a factor 1.8 relative to the rings. Enceladus is closest to the spacecraft here.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was obtained at a distance of approximately 175,000 kilometers (109,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 151 degrees. Image scale is about 3,280 feet (1 kilometer) per pixel on Enceladus.

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

Tuesday, November 8, 2011

Tethys


Saturn's moon Tethys shows off its tortured surface in this Cassini spacecraft image.

On the top left of the image there is huge Odysseus Crater. See PIA07693 for a closer view. On the bottom right there is Ithaca Chasma, a series of scarps that runs north-south across the moon for more than 620 miles (1,000 kilometers). North on Tethys is up and rotated 25 degrees to the right. See PIA07734 and PIA10460 to learn more.

This view looks toward the area between the leading hemisphere and Saturn-facing side of Tethys (660 miles, or 1,062 kilometers across).

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on September 14, 2011. The view was acquired at a distance of approximately 178,000 miles kilometers (287,000) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 11 degrees. Image scale is about 1 mile (2 kilometers) per pixel.

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

Tuesday, November 1, 2011

Hyperion


The sponge-like surface of Saturn's moon Hyperion is highlighted in this Cassini portrait, captured during the spacecraft's September 16, 2011, flyby.

Hyperion (168 miles, or 270 kilometers across) has an irregular shape, and it tumbles through its orbit: that is, it does not spin at a constant rate or in a constant orientation. (A standard reference latitude-longitude system has not yet been devised for this moon.) Images such as this one extend previous coverage and allow a better inventory of the surface features, the satellite's shape and changes in its spin. See PIA06243 and PIA07761 to learn more and to watch a movie.

The image was taken in visible blue light with the Cassini spacecraft narrow-angle camera. The view was obtained at a distance of approximately 55,000 miles (88,000 kilometers) from Hyperion and at a Sun-Hyperion-spacecraft, or phase, angle of 37 degrees. Image scale is 1,720 feet (524 meters) per pixel.

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

Thursday, October 27, 2011

Map of Titan - April 2011


This global digital map of Saturn's moon Titan was created using images taken by the Cassini spacecraft's imaging science subsystem (ISS).

The images were taken using a filter centered at 938 nanometers, allowing researchers to examine variations in albedo (or inherent brightness) variations across the surface of Titan. Because of the scattering of light by Titan's dense atmosphere, no topographic shading is visible in these images.

The map is an equidistant projection and has a scale of 2.5 miles (4 kilometers) per pixel. Actual resolution varies greatly across the map, with the best coverage (close to the map scale) along the equator near the center of the map at 180 degrees west longitude and near the left and right edges at 0 and 360 degrees west longitude. The worst coverage is on the leading hemisphere (particularly around 120 degrees west longitude) and in some northern latitudes. Coverage in the northern polar region continues to improve as the north pole comes out of shadow after Titan's northern vernal equinox in August 2009. Large dark areas, now known to be liquid-hydrocarbon-filled lakes, have been documented at high latitudes (see PIA11146).

This map is an update to the version released in February 2009 (see PIA11149). Data from the last two years, including the most recent data in the map from April 2011, have improved coverage in the southern trailing hemisphere and over portions of the north polar region.

The mean radius of Titan used for projection of this map is 1,600 miles (2,575 kilometers). Titan is assumed to be spherical until a control network -- or model of the moon's shape based on multiple images tied together at defined points on the surface -- is created at some point in the future.

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

Tuesday, October 25, 2011

Titan, Dione, Pan and Pandora with Saturn's Rings


A quartet of Saturn's moons, from tiny to huge, surround and are embedded within the planet's rings in this Cassini composition.

Saturn's largest moon, Titan, is in the background of the image, and the moon's north polar hood is clearly visible. See PIA08137 to learn more about that feature on Titan (3,200 miles, or 5,150 kilometers across). Next, the wispy terrain on the trailing hemisphere of Dione (698 miles, or 1,123 kilometers across) can be seen on that moon which appears just above the rings at the center of the image. See PIA10560 and PIA06163 to learn more about Dione's wisps. Saturn's small moon Pandora (50 miles, or 81 kilometers across) orbits beyond the rings on the right of the image. Finally, Pan (17 miles, or 28 kilometers across) can be seen in the Encke Gap of the A ring on the left of the image.

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

The image was taken in visible blue light with the Cassini spacecraft narrow-angle camera on September 17, 2011. The view was obtained at a distance of approximately 1.3 million miles (2.1 million kilometers) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 27 degrees. Image scale is 8 miles (13 kilometers) per pixel on Dione.

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

Thursday, October 20, 2011

Saturn


The giant planet Saturn, as observed with the VLT NAOS-CONICA Adaptive Optics instrument on December 8, 2001; the distance was 1,209 million km. It is a composite of exposures in two near-infrared wavebands (H and K) and displays well the intricate, banded structure of the planetary atmosphere and the rings. Note also the dark spot at the south pole at the bottom of the image. One of the moons, Tethys, is visible as a small point of light below the planet. It was used to guide the telescope and to perform the adaptive optics "refocusing" for this observation. More details in the text.

This image of Saturn, the second-largest planet in the solar system, was obtained at a time when Saturn was close to summer solstice in the southern hemisphere. At this moment, the tilt of the rings was about as large as it can be, allowing the best possible view of the planet's South Pole. That area was on Saturn's night side in 1982 and could therefore not be photographed during the Voyager encounter. The dark spot close to the South Pole is a remarkable structure that measures approximately 300 km across. The bright spot close to the equator is the remnant of a giant storm in Saturn's extended atmosphere that has lasted more than 5 years.

The present photo provides what is possibly the sharpest view of the ring system ever achieved from a ground-based observatory. Many structures are visible, the most obvious being the main ring sections, the inner C-region (here comparatively dark), the middle B-region (here relatively bright) and the outer A-region, and also the obvious dark "divisions," including the well-known, broad Cassini division between the A- and B-regions, as well as the Encke division close to the external edge of the A-region and the Colombo division in the C-region. Moreover, many narrow rings can be seen at this high image resolution, in particular within the C-region.

Photo credit: ESO

Wednesday, October 19, 2011

Enceladus


The Cassini spacecraft takes a close view of some of the southern terrain of Saturn's moon Enceladus, where newly created terrain is on display.

See PIA11685 for a mosaic of this geologically active moon's leading hemisphere that shows the more recently created terrain of the south polar region meeting older, crater-filled terrain farther north. The area shown here is between the leading hemisphere and Saturn-facing side of Enceladus (313 miles, or 504 kilometers across). This view is centered on terrain at 35 degrees south latitude, 45 degrees west longitude. North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on September 13, 2011. The view was acquired at a distance of approximately 26,000 miles (42,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 52 degrees. Image scale is 830 feet (253 meters) per pixel.

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

Tuesday, October 11, 2011

Pendent Pair


A pair of Saturn's moons appears as if hung below the planet's rings in this Cassini spacecraft view.

Enceladus (313 miles, or 504 kilometers across) appears just below the rings here, near the center of the image. Tethys (660 miles, or 1,062 kilometers across) is near the bottom center of the image. Tethys is closer to Cassini than is Enceladus.

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

The image was taken in visible light with the Cassini spacecraft wide-angle camera on September 13, 2011. The view was obtained at a distance of approximately 169,000 miles (272,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 135 degrees. The view was obtained at a distance of approximately 129,000 miles (208,000 kilometers) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 135 degrees. Image scale is 10 miles (16 kilometers) per pixel on Enceladus and 7 miles (12 kilometers) per pixel on Tethys.

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

Thursday, October 6, 2011

Enceladus


NASA's Cassini spacecraft successfully completed its October 1 flyby of Saturn's moon Enceladus and its jets of water vapor and ice. At its closest approach, the spacecraft flew approximately 62 miles (100 kilometers) above the moon's surface. The close approach was designed to give some of Cassini's instruments, including the ion and neutral mass spectrometer, the chance to "taste" the jets themselves.

At a higher vantage point during the encounter, Cassini's high-resolution camera captured pictures of the jets emanating from the moon's south polar region. The latest raw images of Enceladus are online at: http://saturn.jpl.nasa.gov/photos/raw/.

The images of the surface include previously seen leading-hemisphere terrain. However, during this encounter, multi-spectral imaging of these terrains extended farther into the ultraviolet region of the electromagnetic spectrum than had previously been achieved at this resolution. By looking at the surface at ultraviolet wavelengths, scientists can better detect the difference between surface materials and shadows than they can at visible wavelengths, where icy materials are highly reflective and shadows are washed out. With both ultraviolet and visible images of the same terrain available to them, scientists will better understand how the surface coverage of icy particles coming from the vents and plumes changes with terrain type and age.

Cassini's next pass of this fascinating moon will be October 19, when the spacecraft flies by at an altitude of approximately 765 miles (1231 kilometers).

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

Wednesday, October 5, 2011

Saturn's Lengthening Shadows


The Cassini spacecraft watches as the shadows of Saturn's rings grow wider and creep farther south as the seasons progress from the planet's August 2009 equinox.

See PIA11667 to learn more about the changing seasons and to see a view from equinox when the rings cast only a thin shadow on Saturn's equator. See PIA09793 for an even earlier view of the rings' wide shadows draped high on the northern hemisphere.

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

The image was taken with the Cassini spacecraft wide-angle camera on August 22, 2011 using a spectral filter sensitive to wavelengths of near-infrared light centered at 939 nanometers. The view was acquired at a distance of approximately 252,000 miles (405,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. Image scale is 13 miles (21 kilometers) per pixel.

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