Sunglint South of Titan's Kraken Mare

This near-infrared, color mosaic from NASA's Cassini spacecraft shows the sun glinting off of Titan's north polar seas. While Cassini has captured, separately, views of the polar seas (see PIA17470) and the sun glinting off of them (see PIA12481 and PIA18433) in the past, this is the first time both have been seen together in the same view.

The sunglint, also called a specular reflection, is the bright area near the 11 o'clock position at upper left. This mirror-like reflection, known as the specular point, is in the south of Titan's largest sea, Kraken Mare, just north of an island archipelago separating two separate parts of the sea.

This particular sunglint was so bright as to saturate the detector of Cassini's Visual and Infrared Mapping Spectrometer (VIMS) instrument, which captures the view. It is also the sunglint seen with the highest observation elevation so far -- the sun was a full 40 degrees above the horizon as seen from Kraken Mare at this time -- much higher than the 22 degrees seen in PIA18433. Because it was so bright, this glint was visible through the haze at much lower wavelengths than before, down to 1.3 microns.

The southern portion of Kraken Mare (the area surrounding the specular feature toward upper left) displays a "bathtub ring" -- a bright margin of evaporate deposits -- which indicates that the sea was larger at some point in the past and has become smaller due to evaporation. The deposits are material left behind after the methane & ethane liquid evaporates, somewhat akin to the saline crust on a salt flat.

The highest resolution data from this flyby -- the area seen immediately to the right of the sunglint -- cover the labyrinth of channels that connect Kraken Mare to another large sea, Ligeia Mare. Ligeia Mare itself is partially covered in its northern reaches by a bright, arrow-shaped complex of clouds. The clouds are made of liquid methane droplets, and could be actively refilling the lakes with rainfall.

The view was acquired during Cassini's August 21, 2014, flyby of Titan, also referred to as "T104" by the Cassini team.

The view contains real color information, although it is not the natural color the human eye would see. Here, red in the image corresponds to 5.0 microns, green to 2.0 microns, and blue to 1.3 microns. These wavelengths correspond to atmospheric windows through which Titan's surface is visible. The unaided human eye would see nothing but haze, as in PIA12528.

Image credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

Note: For more information, see PIA18433: Sunglint on a Hydrocarbon Lake and Cassini Sees Sunny Seas on Titan.

Titan's South Polar Vortex

These two views of Saturn's moon Titan show the southern polar vortex, a huge, swirling cloud that was first observed by NASA's Cassini spacecraft in 2012.

The view at left is a spectral map of Titan obtained with the Cassini Visual and Infrared Mapping Spectrometer (VIMS) on November 29, 2012. The inset image is a natural-color close-up of the polar vortex taken by Cassini's wide-angle camera (part of the view previously released as PIA14925).

Three distinct components are evident in the VIMS image, represented by different colors: the surface of Titan (orange, near center), atmospheric haze along the limb (light green, at top) and the polar vortex (blue, at lower left).

To the VIMS instrument, the spectrum of the southern polar vortex shows a remarkable difference with respect to other portions of Titan's atmosphere: a signature of frozen hydrogen cyanide molecules (HCN). This discovery has suggested to researchers that the atmosphere of Titan's southern hemisphere is cooling much faster than expected. Observing seasonal shifts like this in the moon's climate is a major goal for Cassini's current extended mission.

Image credit: NASA/JPL-Caltech/ASI/University of Arizona/SSI/Leiden Observatory and SRON

Note: For more information, see Titan's Swirling Polar Cloud is Cold and Toxic (ESA) and Swirling Cloud at Titan's Pole is Cold and Toxic (JPL).

Unusual Changing Feature in Titan's Ligeia Mare

These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn's moon Titan. The views, taken during three different Cassini flybys of Titan, show that this feature was not visible in earlier radar images of the same region and its appearance changed between 2013 and 2014.

In the images, the dark areas represent the sea, which is thought to be composed of mostly methane and ethane. Most of the bright areas represent land surface above or just beneath the water line. The mysterious bright feature appears off the coast below center in the middle and right images.

The mystery feature had not been seen in preceding SAR observations of the region from 2007 to 2009. After its first appearance in early July 2013, it was not visible in observations by Cassini's Visible and Infrared Mapping Spectrometer, obtained later in July and in September 2013. Low-resolution SAR images obtained in October 2013 also failed to recover the feature.

The SAR observation from Cassini's August 21, 2014 Titan flyby shows that the feature was still visible, although its appearance changed during the 11 months since it was last observed. The feature seems to have changed in size between the images from 2013 and 2014 -- doubling from about 30 square miles (about 75 square kilometers) to about 60 square miles (about 160 square kilometers). Ongoing analyses of these data may eliminate some of the explanations previously put forward, or reveal new clues as to what is happening in Titan's seas.

The Cassini radar team is investigating possible origins for the feature, including surface waves, rising bubbles, floating solids, solids that are suspended just below the surface or perhaps something more exotic. Researchers suspect that the appearance of this feature could be related to changing seasons on Titan, as summer draws near in the moon's northern hemisphere. Monitoring such changes is a major goal for Cassini's current extended mission.

The upper half of the middle image uses data from the April 26, 2007 Titan flyby. That area did not receive SAR coverage during the July 10, 2013 encounter, so the earlier data was used to fill-in the scene.

Image credit: NASA/JPL-Caltech/ASI/Cornell

Artist's Conception of Cassini Observing Sunsets on Titan

Using data collected by Cassini's Visual and Infrared Mapping Spectrometer, or VIMS, while observing Titan's sunsets, researchers created simulated spectra of Titan as if it were a planet transiting across the face of a distant star. The research helps scientists to better understand observations of exoplanets with hazy atmospheres.

Image Credit: NASA/JPL-Caltech

Note: For more information, see Sunsets on Titan Reveal the Complexity of Hazy Exoplanets.

Saturn's Auroras

Ultraviolet and infrared images from NASA's Cassini spacecraft and Hubble Space Telescope show active and quiet auroras at Saturn's north and south poles.

Saturn's auroras glow when energetic electrons dive into the planet's atmosphere and collide with hydrogen molecules. Sometimes a blast of fast solar wind, composed of mostly electrons and protons, creates an active aurora at Saturn, as occurred on April 5 and May 20, 2013.

The first set of images, as seen in the ultraviolet part of the spectrum by Hubble, shows an active aurora dancing around Saturn's north pole on April 5. The movie then shows a relatively quiet time between April 19 to 22 and between May 18 and 19. The aurora flares up again in Hubble images from May 20. This version, shown in false-color, has been processed to show the auroras more clearly.

A second set of ultraviolet images shows a closer view of an active north polar aurora in white. This set comes from Cassini ultraviolet imaging spectrograph observations on May 20 and 21.

The last set of images, in the infrared, shows a quiet southern aurora (in green) in observations from Cassini's visual and infrared mapping spectrometer on May 17. Saturn's inner heat glows in red, with dark areas showing where high clouds block the heat.

Video credit: NASA/JPL-Caltech/University of Colorado/Central Arizona College and NASA/ESA/University of Leicester and NASA/JPL-Caltech/University of Arizona/Lancaster University

Note: For more information, see PIA17668: Saturn's Colorful Aurora, NASA Spacecraft Get a 360-Degree View of Saturn's Auroras and PIA17669: Pulses from the Sun.

Titan's North Polar Lakes and Evaporite Deposits

This false-color mosaic, made from infrared data collected by NASA's Cassini spacecraft, reveals the differences in the composition of surface materials around hydrocarbon lakes at Titan, Saturn's largest moon. Titan is the only other place in the solar system that we know has stable liquid on its surface, though its lakes are made of liquid ethane and methane rather than liquid water. While there is one large lake and a few smaller ones near Titan's south pole, almost all of Titan's lakes appear near the moon's north pole.

Scientists mapped near-infrared colors onto the visible color spectrum. Red in this image was assigned a wavelength of 5 microns (10 times longer than visible light), green 2.0 microns (four times longer than visible light), and blue 1.3 microns (2.6 times longer than visible light).

The orange areas are thought to be evaporite -- the Titan equivalent of salt flats on Earth. The evaporated material is thought to be organic chemicals originally from Titan's haze particles that once dissolved in liquid methane. They appear orange in this image against the greenish backdrop of Titan's typical bedrock of water ice.

In this mosaic, Kraken Mare, which is Titan's largest sea and covers about the same area as Earth's Caspian Sea and Lake Superior combined, can be seen spreading out with many tendrils on the upper right,. The big dark zone up and left of Kraken is Ligeia Mare, the second largest sea. Below Ligeia, shaped similar to a sports fan's foam finger that points just up from left, is Punga Mare, the third largest Titan Sea. Numerous other smaller lakes dot the area. Titan's north pole is located in the geographic location just above the end of the "finger" of Punga Mare.

Figure 1 highlights a high-resolution strip and shows the north pole marked with a red cross. Other smaller lakes are also labeled.

The data shown here were obtained by Cassini's visual and infrared mapping spectrometer during a close flyby of Titan on September 12, 2013.

Until now, the spectrometer has only been able to capture distant, oblique or partial views of this area. The September 12, 2013, flyby provided better viewing geometry. And sunlight has begun to pierce the winter darkness that shrouded Titan's north pole at the time of Cassini's arrival in the Saturn system nine years ago. A thick cap of haze that once hung over the north pole has also dissipated as northern summer approaches. And, thankfully, Titan's beautiful, almost cloudless, rain-free weather continued during this flyby.

The resolution varies across this composite view depending on when each cube of data was acquired, but the best surface sampling is 2 miles (3 kilometers) per pixel.

Views of this area by other Cassini instruments include PIA17471, PIA17472, PIA17473 and PIA14584 from the imaging science subsystem; and PIA10008 and PIA17031 from the radar mapper. An earlier VIMS view can be seen at PIA16845.

Image credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

Note: For more information, see Cassini Gets New Views of Titan's Land of Lakes.

Saturn and Rings in Infrared

This colorized mosaic from NASA's Cassini mission shows an infrared view of the Saturn system, backlit by the sun, from July 19, 2013. The image, made from data obtained by Cassini's visual and infrared mapping spectrometer, covers a swath of Saturn and its rings about 340,000 miles (540,000 kilometers) across that includes the planet and its rings out to the diffuse E ring, Saturn's second most distant ring. The mosaic covers an area about 9,800 miles (16,000 kilometers) from top to bottom.

When Saturn is blocking the direct light of the sun, scientists can get a better look at the fainter rings. When small particles are lit from behind, they show up like fog in the headlights of an oncoming vehicle. Conversely, a ring that is easily seen from Earth because it is densely packed with chunks of bright water ice looks dark in these images because it is so thick that it blocks almost all of the sunlight shining behind it.

Looking at Saturn in the infrared spectrum can tell scientists more about the sizes of the particles in the fainter rings, and how these sizes vary with location in the rings. Infrared data also provide clues to ring particles' chemical composition.

Looking at the Saturn system in infrared light also shows thermal, or heat, radiation, so while a visible-light image from this vantage point would simply show the face of the planet as dimly lit by sunlight reflected off the rings, Saturn glows brightly in this view with the heat from Saturn's interior.

The visual and infrared spectrometer team colorized the image by assigning blue to radiation detected in the 1.5-to-1.19-micron range, green to radiation detected in the 1.9-to-2.1-micron range and red to the radiation detected in the 4.88-to-5.06-micron range.

Image credit: NASA/JPL-Caltech/University of Arizona/Cornell

Note: For more information, see PIA17469: High-Contrast Infrared Scan of Saturn and its Rings and Rings, Dark Side of Saturn Glow in New Cassini Image.

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.

Titan's Ligeia Mare and Other Lakes

These images from NASA's Cassini spacecraft show one of the large seas and a bounty of smaller lakes on Saturn's moon Titan. Scientists saw these small lakes in data obtained by both Cassini's visual and infrared mapping spectrometer (left) and radar instrument (right).

Ligeia Mare, about 50,000 square miles (125,000 square kilometers) in area, is the large lake near the bottom of both images. Three new lakes of about 100 to 300 square miles (a few hundreds of square kilometers) identified first in the visual and infrared mapping spectrometer images are labeled in the annotated version as Freeman (VimsNN1), Cardiel (VimsNN2) and VimsNN4. The new lakes can be seen at the top left and middle right. The small lake Towada first seen in radar images was also seen in this VIMS investigation (VimsNN3) and can be seen in the middle right.

The images that went into the VIMS mosaic were taken in June 2010. The images that make up the radar mosaic were taken in April 2007. The small lakes remained relatively consistent between 2007 and 2010.

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

Note: For more information, see Titan's Methane: Going, Going, Soon to Be Gone?

Small Lakes on Titan

Three new small lakes, 100 to 300 square miles (a few hundreds of square kilometers) in surface area, have been identified on Saturn's moon Titan in data from NASA's Cassini spacecraft. In the image from Cassini's visual and infrared mapping spectrometer at the bottom part of the image, Freeman, Cardiel and a lake currently designated as VIMSNN4 join the cast of small lakes already discovered by Cassini's radar. Towada (VIMSNN3) is a lake originally seen in radar data that was also seen in the VIMS data. Radar views of some of the lakes are shown as the insets.

Studies of the surface areas of these small lakes can yield big results in determining the evolution of liquid bodies on Titan, and shed light on the past and future of methane in shaping Titan's environment.

The VIMS images were taken in 2010. The radar images were taken in 2007.

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

Note: For more information, see Titan's Methane: Going, Going, Soon to Be Gone?

Wetlands on Titan

A dense network of small rivers or swampy areas appears to connect some of the seas on Saturn's moon Titan, as seen in this comparison of data of the same area from two instruments on NASA's Cassini spacecraft. Images from the radar instrument are on the left and images from the visual and infrared mapping spectrometer (VIMS) are on the right.

At approximately 50,000 square miles (about 125,000 square kilometers), Ligeia Mare (middle of the images) is larger than any North American lake. The labels K1, K2, and K3 in the radar mosaic (a) refer to different parts of Kraken Mare that appear interconnected in the VIMS mosaic (b).

Photo credit: NASA/JPL-Caltech/University of Arizona

Note: For more information, see Titan's Methane: Going, Going, Soon to Be Gone?

Formation of a High-Altitude Hood Over Titan's South Pole

False-color images from NASA's Cassini spacecraft show the development of a hood of high-altitude haze -- which appears orange in this image -- forming over the south pole of Saturn's moon Titan. These images were obtained on May 22 and June 7, 2012 by the visual and infrared mapping spectrometer in infrared wavelengths. Scientists assigned the colors red, green and blue to wavelengths mostly sensitive to the stratosphere, troposphere, and surface components, respectively. The newly discovered feature appears several hundred miles (kilometers) above the surface. When Cassini arrived at Saturn, it saw a hood of clouds and haze over Titan's north pole, which was experiencing winter. The south pole was basically clear, except for sporadic methane clouds. The seasons have been changing and the circulation in the upper atmosphere goes now from the illuminated north pole to the cooling south pole, causing downwellings over the south pole and formation of the hood.

Photo credit: NASA/JPL-Caltech/University of Arizona/LPGNantes

Changes in Titan's North Polar Cloud

This series of images obtained by NASA's Cassini spacecraft shows several views of the north polar cloud covering Saturn's moon Titan. The false-color images were obtained by Cassini's Visual and Infrared Mapping Spectrometer (VIMS). They can be seen on the left of each pair of images, with that same image re-projected onto a globe of Titan on the right. The global image shows Titan's north pole at the center. Other parts of the Titan globe are filled in using data from Cassini's imaging cameras and radar instrument.

The VIMS images cover 2006 to 2009, when Titan was transitioning from northern winter to northern spring. In 2006, the north polar cloud appeared dense and opaque. But in spectrometer images obtained around the 2009 equinox, when the Sun was directly over Saturn and Titan's equators and northern winter was turning into spring, the cloud appeared much thinner and patchier. It allowed scientists to see the underlying northern lakes and seas on the surface, including Kraken Mare (at the end of the red arrows). The northern seas and lakes, made of liquid hydrocarbons, look like dark jigsaw puzzle pieces in the false-color images.

Scientists colorized the VIMS image by assigning red, green and blue to the parts of the infrared spectrum around 5 micrometers, 2.8 micrometers and 2.03 micrometers, respectively. The images create a kind of time-lapse series from December 28, 2006 to June 6, 2009, from the 23rd, 24th, 30th, 43rd, 44th, 45th, 52nd, 53rd, 55th and 57th time Cassini flew by Titan. (Planning changes early in the orbital tour meant that even though a Titan flyby might be called "T22," it was actually the 23rd flyby of Titan.)

For a view of just the VIMS images, see PIA15230.

Photo credit: NASA/JPL-Caltech/University of Arizona/CNRS/LPGNantes

Snapshots of Titan's North Polar Cloud

This series of false-color images obtained by NASA's Cassini spacecraft shows the dissolving cloud cover over the north pole of Saturn's moon Titan. The images, obtained by Cassini's Visual and Infrared Mapping Spectrometer (VIMS), cover 2006 to 2009, when Titan was transitioning from northern winter to northern spring. In 2006, the north polar cloud appeared dense and opaque. But in spectrometer images obtained around the 2009 equinox, when the Sun was directly over Saturn and Titan's equators and northern winter was turning into spring, the cloud appeared much thinner and patchier. The dissipating cloud allowed scientists to see the underlying northern lakes and seas, including Kraken Mare. The northern seas and lakes on the surface below, made of liquid hydrocarbons, look like dark jigsaw puzzle pieces in the false-color images.

Scientists colorized the VIMS image by assigning red, green and blue to the parts of the infrared spectrum around 5 micrometers, 2.8 micrometers and 2.03 micrometers, respectively. The images create a kind of time-lapse series from December 28, 2006 to June 6, 2009.

For another view of these images, see PIA15231.

Photo credit: NASA/JPL-Caltech/University of Arizona/CNRS/LPGNantes

Updrafts of Large Ammonia Crystals in Saturn Storm

This false-color infrared image, obtained by NASA's Cassini spacecraft, shows clouds of large ammonia ice particles dredged up by a powerful storm in Saturn's northern hemisphere. Large updrafts dragged ammonia gas upward more than 30 miles (50 kilometers) from below. The ammonia then condensed into large crystals in the frigid upper atmosphere. This storm is the most violent ever observed at Saturn by an orbiting spacecraft.

Cassini's visual and infrared mapping spectrometer obtained these images on Feb. 24, 2011. Scientists colorized the image by assigning red to brightness detected from the 4.08-micron wavelength, green to brightness from the 0.90-micron wavelength, and blue to brightness from the 2.73-micron wavelength. Large particles (red) reflect sunlight well at 4.08 microns. Particles at high altitude (green) reflect sunlight well at 0.9 microns. Particles comprised of ammonia -- especially large ones -- do not reflect 2.73-micron sunlight well, but instead absorb light at this wavelength.

The storm here shows up as yellow, demonstrating that it has a large signal in both red and green colors. This indicates the cloud has large particles and extends upward to relatively high altitude. In addition, the lack of blue in the feature indicates that the storm cloud has a substantial component of ammonia crystals. The head of the storm is particularly rich in such particles, as created by powerful updrafts of ammonia gas from depth in the throes of Saturn's thunderstorm.

Photo credit: NASA/JPL/Univ. of Arizona

Titan's Sotra Facula

This movie is based on data from NASA's Cassini spacecraft and shows a flyover of an area of Saturn's moon Titan known as Sotra Facula. Scientists believe Sotra is the best case for an ice volcano -- or cryovolcano -- region on Titan.

The flyover shows two peaks more than 1,000 meters (3,000 feet) tall and multiple craters as deep as 1,500 meters (5,000 feet). It also shows finger-like flows. All of these are land features that indicate cryovolcanism. The 3-D topography comes from Cassini's radar instrument. Topography has been vertically exaggerated by a factor of 10. The false color in the initial frames shows different compositions of surface material as detected by Cassini's visual and infrared mapping spectrometer. In this color scheme, dunes tend to look relatively brown-blue. Blue suggests the presence of some exposed ice. Scientists think the bright areas have an organic coating that hides the ice and is different and lighter than the dunes. The finger-like flows appear bright yellowish-white, like the mountain and caldera. The second set of colors shows elevation, with blue being lowest and yellow and white being the highest. Dunes here appear blue because they tend to occupy low areas. The finger-like flows are harder to see in the elevation data, indicating that they are thin, maybe less than about 100 meters (300 feet) thick.

Photo credit: NASA/JPL-Caltech/USGS/University of Arizona

Notes: For a map showing Sotra Facula's location on Titan, see PIA13696: Global View of Sotra Facula, Titan. Also, this is Saturnology's 100th post!

Titan's Cloud Coverage - July 2004-April 2010

This graphic, constructed from data obtained by NASA's Cassini spacecraft, shows the percentage of cloud coverage across the surface of Saturn's moon Titan. The color scale from black to yellow signifies no cloud coverage to complete cloud coverage, over a period spanning July 2004 to April 2010.

Equinox, when the Sun shone directly over the equator, occurred in August 2009. It brought a changing of the seasons, as Titan moved out of southern summer into northern spring.

During winter in the northern hemisphere, northern polar clouds of ethane formed in Titan's troposphere, the lowest part of the atmosphere, from a constant influx of ethane and aerosols from a higher part of the atmosphere known as the stratosphere. In the southern hemisphere, atmospheric gases enriched with methane welled up from the surface to produce mid- and high-latitude clouds.

The amount and location of cloud coverage on Titan provide clues to seasonal changes on the moon. During southern summer, Cassini scientists saw a thick vortex of clouds at Titan's north pole, and a thinner patch at the south pole. Wispier mid-latitude clouds sometimes appeared in the southern temperate zones. Scientists are closely watching to see if this picture will change as northern summer approaches. They will observe whether the south polar clouds grow as the north polar clouds dissipate, and whether northern temperate clouds appear as those in the south disappear.

The data for this graphic came from Cassini's visual and infrared mapping spectrometer.

Photo credit: NASA/JPL/University of Arizona/University of Nantes/University of Paris Diderot

Clouds Clearing Around Titan's North Pole

This pair of false-color images, made from data obtained by NASA's Cassini spacecraft, shows clouds covering parts of Saturn's moon Titan in yellow. Based on the way near-infrared channels of light were color-coded, cloud cover appears yellow, while Titan's hazy atmosphere appears magenta. The images show cloud cover dissolving from Titan's north polar region between May 12, 2008 (left), and December 12, 2009 (right). The clouds in the second image appear around 40 degrees south latitude, still active late after Titan's equinox.

Cassini's first observations of clouds near this latitude occurred during summer in the southern hemisphere. Equinox, when the Sun shone directly over the equator, occurred in August 2009. It brought a changing of the seasons, as Titan moved out of southern summer into northern spring.

For the past six years, Cassini has observed clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. Now scientists are seeing evidence of seasonal circulation turnover at Titan. Clouds at the south pole disappeared just before equinox and the clouds in the north are thinning out. This activity agrees with models that predict cloud activity reversing from one hemisphere to another.

During winter in the northern hemisphere, northern polar clouds of ethane formed in Titan's troposphere, the lowest part of the atmosphere, from a constant influx of ethane and aerosols from a higher part of the atmosphere known as the stratosphere. In the southern hemisphere, atmospheric gases enriched with methane welled up from the surface to produce mid- and high-latitude clouds.

The data for the images was detected by Cassini's visual and infrared mapping spectrometer in near-infrared wavelengths. Scientists focused on three wavelengths of infrared radiation that were particularly good for observing cloud signatures and assigned them red, green and blue channels. Emissions in the 2 micron wavelength of light, colored red, detect the Titan surface. Emissions in the 2.11 micron wavelength, colored green, detect the lowest part of the Titan atmosphere, or troposphere. Emissions at the 2.21 micron wavelength, colored blue, detect the hazy stratosphere, a higher part of the atmosphere. The clouds appear yellowish because they lit up the channels designated red and green, but not the blue channel.

Photo credit: NASA/JPL/University of Arizona/University of Nantes/University of Paris Diderot

Enhanced-Color Maps of Saturn's Inner Moons

This set of enhanced-color maps made from data obtained by NASA's Cassini spacecraft show Saturn's moons Mimas, Enceladus, Tethys, Dione and Rhea. The global maps show the colorful splotches and bands on the icy moons' surfaces that scientists believe came from bombardments large and small.

Icy material sprayed by Enceladus, which makes up the misty E ring around Saturn, appears to leave a brighter, blue signature. The pattern of bluish material on Enceladus, for example, indicates that the moon is covered by the fallback of its own "breath."

Enceladean spray also appears to splatter the parts of Tethys, Dione and Rhea that run into the spray head-on in their orbits around Saturn. But scientists are still puzzling over why the Enceladean frost on the leading hemisphere of these moons bears a coral-colored, rather than bluish, tint.

On Tethys, Dione and Rhea, darker, rust-colored reddish hues paint the entire trailing hemisphere, or the side that faces backward in the orbit around Saturn. The reddish hues are thought to be caused by tiny particle strikes from circulating plasma, a gas-like state of matter so hot that atoms split into an ion and an electron, in Saturn's magnetic environment. Tiny, iron-rich "nanoparticles" may also be involved, based on earlier analyses by the Cassini visual and infrared mapping spectrometer team.

Mimas is touched by the tint of Enceladean spray, but it appears on the trailing side of Mimas. This probably occurs because it orbits inside the path of Enceladus, or closer to Saturn, than Tethys, Dione and Rhea.

Mimas and Tethys also sport a dark, bluish band. The bands match 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 on Mimas, but the electrons appear to be zapping the surface in a way that matches the Pac-Man pattern detected by Cassini's composite infrared spectrometer.

On Rhea, a unique chain of bluish splotches appears where fresh, bluish ice has been exposed on older crater rims. Cassini imaging scientists recently reported that they did not see evidence in Cassini images of a ring around Rhea. However, scientists analyzing these new enhanced-color maps suggest the crash of orbiting material, perhaps a ring, to the surface of Rhea in the not too distant past, could explain the bluish splotches.

These new maps were 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 maps are in a simple cylindrical projection from 90 degrees south latitude (bottom) to 90 degrees north latitude (top). From left to right, they cover 360 degrees west longitude to minus 2 degrees west longitude. The leading hemisphere appears on the right side of each map and trailing hemisphere appears on the left.

Photo credit: NASA/JPL/SSI/LPI

Tinted Rhea

These three views of Saturn's moon Rhea were made from data obtained by NASA's Cassini spacecraft, enhanced to show colorful splotches and bands on the icy moon's surface. Scientists believe the reddish and bluish tints came from bombardments large and small.

Icy material sprayed by the moon Enceladus hits Rhea head-on in its orbit around Saturn and leaves a coral-colored tint. Darker, rust-colored reddish hues paint the trailing hemisphere, or the side that faces backward in the moon's orbit around Saturn. The reddish hues are thought to be caused by tiny particle strikes from circulating plasma, a gas-like state of matter so hot that atoms split into an ion and an electron, in Saturn's magnetic environment. Tiny, iron-rich "nanoparticles" may also be involved, based on earlier analyses by the Cassini visual and infrared mapping spectrometer team.

Rhea sports a chain of bluish splotches along the equator that appear where fresh, bluish ice has been exposed on older crater rims. Cassini imaging scientists recently reported that they did not see evidence in Cassini images of a ring around Rhea. However, scientists analyzing these enhanced-color views suggest the bluish material could have been exposed by the crash of orbiting material -- perhaps a ring -- to the surface of Rhea in the not too distant past.

These images were made by processing raw images obtained by Cassini's imaging cameras in November 2005. 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 image on the left shows a composite image made from data in the infrared, green and ultraviolet filters. The middle view shows an image made from data analyzing the ratio of infrared to green wavelengths, indicating the relative redness of the features. The brighter the feature is in this middle view, the redder it is. The image on the right shows data analyzing the ratio of infrared to ultraviolet wavelengths. The darker the feature is, the bluer the tint

In each of these images, the trailing hemisphere is on the left side and leading hemisphere is on the right side. They are centered near 145 degrees west longitude, about 35 degrees east of the boundary between the leading and trailing hemispheres. The bright crater Inktomi can be seen near the center of the images on the left and right, but was more difficult to see in the middle image because of there is less contrast in the infrared/ultraviolet ratio.

Photo credit: NASA/JPL/SSI/LPI

Note: For a brief technical discussion about how Rhea got its tints, see PIA13425: Moons Under Bombardment.