Rhea's Northern Craters

The Cassini spacecraft captured this high-resolution view of the cratered surface of Saturn's moon Rhea as the spacecraft flew by the moon on October 17, 2010.

For closer views of Rhea's surface from earlier flybys, see PIA07765 and PIA08402. This view is centered on terrain at 60 degrees North latitude, 251 degrees West longitude on Rhea (1,528 kilometers, 949 miles across).

The image was taken in visible light with the Cassini spacecraft's narrow-angle camera. The view was acquired at a distance of approximately 40,000 kilometers (25,000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 88 degrees. Image scale is 238 meters (781 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Saturn's Plasma and Radio Waves, as Seen by Cassini

This animation, derived from data obtained by NASA's Cassini spacecraft, shows how plasma swirling around Saturn is correlated to bursts of radio waves emanating from the planet. The data shown on the upper portion of the screen were obtained by the ion and neutral camera, part of the magnetospheric imaging instrument. When the plasma gets hot, it goes from red to white. The bottom part of the screen shows data from Cassini's radio and plasma wave subsystem. The data were obtained from 12:01 a.m. UTC to 11:55 a.m. UTC on October 7, 2008.

Video credit: NASA/JPL/JHUAPL/University of Iowa

Saturn's Hot Plasma Explosions

This animation based on data obtained by NASA's Cassini spacecraft shows how the "explosions" of hot plasma on the night side (orange and white) periodically inflate Saturn's magnetic field (white lines). Cassini scientists have been able to compute the "pressure" that the hot plasma exerts on the surrounding magnetic field by using remote images of the previously invisible hot plasma taken by the ion and neutral camera, part of the magnetospheric imaging instrument on board Cassini.

These enormous clouds of hot plasma recur in the part of the magnetosphere known as the magnetotail roughly every 10 to 11 hours. They rotate around Saturn at a distance of about eight to 15 times the radius of Saturn. Scientists have finally been able to demonstrate that the pressure contained in these clouds is sufficient to inflate the magnetic field in a manner that is consistent with the periodic magnetic field signals that have puzzled them for so long. As the high- and low-pressure systems of atmospheric weather on Earth produce winds, pressures in space produce huge electrical currents, which in turn distort the magnetic field.

The animation is based on data that were collected from December 17 to 18, 2004.

Video credit: NASA/JPL/JHUAPL/University of Iowa

Note: For more information, see Hot Plasma Explosions Inflate Saturn's Magnetic Field.

Rhea's Western Wisps

Icy fractures on Saturn's moon Rhea reflect sunlight brightly in this high-resolution mosaic created from images captured by NASA's Cassini spacecraft during its March 2, 2010, flyby. This flyby was the closest flyby of Rhea up to then.

This mosaic of six images shows the westernmost portion of the moon's "wispy" terrain. (See PIA06578 and PIA08120 to learn more.) Among the interesting features depicted here is a very straight east-west fracture near the top center of the mosaic that intersects two north-south fractures. The large crater at the bottom left of the mosaic is Inmar (55 kilometers, 34 miles across).

The closest approach of the spacecraft to Rhea during this encounter was 100 kilometers (62 miles). These images were obtained approximately half an hour later at an altitude of about 16,000 kilometers (10,000 miles).

This mosaic shows part of the side of Rhea (1528 kilometers, 949 miles across) that always faces Saturn. The images were re-projected in an orthographic projection centered on terrain at 7 degrees North latitude, 296 degrees West longitude. The mosaic itself shows terrain centered on terrain at 6 degrees North latitude, 293 degrees West longitude. North on Rhea is roughly up in the image.

The images were taken with the Cassini spacecraft narrow-angle camera. The view was obtained at a Sun-Rhea-spacecraft, or phase, angle of 2 degrees. So, Cassini was almost directly between Rhea and the Sun as it acquired these images. Image scale is 85 meters (280 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Seven Lacuna Names Approved for Use on Titan

From the USGS Astrogeology Science Center:

Seven names with the descriptor term lacuna have been approved for use on Titan. For more information, see the list of Titan lacunae and the map of the north polar region of Titan in the Gazetteer of Planetary Nomenclature.

Note: The official definition of a lacuna (pl., lacunae) is an "Irregularly shaped depression on Titan having the appearance of a dry lake bed." The seven new lacunae are: Atacama Lacuna, Eyre Lacuna, Jerid Lacuna, Melrhir Lacuna, Ngami Lacuna, Racetrack Lacuna and Uyuni Lacuna.

Titan and Tethys

The Cassini spacecraft watches a pair of Saturn's moons, showing the hazy orb of giant Titan beyond smaller Tethys.

In the foreground of the image, Ithaca Chasma can be seen running roughly north-south for more than 1,000 kilometers (620 miles) on Tethys. See PIA07734 for a closer view. Titan's detached, high-altitude haze layer and north polar hood are also visible here. See PIA09739 and PIA08137 to learn more.

This view looks toward the Saturn-facing sides of Titan (5,150 kilometers, or 3,200 miles across) and Tethys (1,062 kilometers, or 660 miles across).

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on October 18, 2010. The view was obtained at a distance of approximately 2.5 million kilometers (1.6 million miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 55 degrees. The view was obtained at a distance of approximately 1.5 million kilometers (930,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 55 degrees. Image scale is 15 kilometers (9 miles) per pixel on Titan and 9 kilometers (6 miles) per pixel on Tethys.

Photo credit: NASA/JPL/Space Science Institute

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!

Saturn, Rhea and Shadows

Shadows adorn Saturn in this Cassini spacecraft view, which also includes the moon Rhea.

Rhea (1,528 kilometers, 949 miles across) is shown orbiting between the planet and the spacecraft and appears above the rings on the left of the image. As Saturn's northern hemisphere experiences spring, the rings now cast a shadow onto the southern hemisphere. The moon Mimas casts a small shadow on the planet south of shadows cast by the rings. The larger, elongated shadow farther south is cast by the moon Dione. Mimas and Dione are not shown.

This view looks toward the southern, unilluminated side of the rings from about 1 degree below the ringplane.

The image was taken in visible red light with the Cassini spacecraft wide-angle camera on October 22, 2010. The view was obtained at a distance of approximately 2.4 million kilometers (1.5 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 84 degrees. Image scale is 141 kilometers (88 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Dione's Erulus Crater

The Cassini spacecraft snapped this shot of cratered Dione as it flew by the Saturnian moon on October 17, 2010.

The large crater at the center of the image is Erulus, which is about 120 kilometers, or 75 miles, across. This view looks toward the southern latitudes of the leading hemisphere of Dione (1,123 kilometers, or 698 miles across).

The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 41,000 kilometers (25,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 53 degrees. Image scale is 240 meters (787 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Map of Tethys

This global map of Saturn's moon Tethys was created using images taken by NASA's Cassini spacecraft.

This map is an update to the version released in February 2010 (see PIA12560). New data collected during Cassini's August 14, 2010, flyby of the moon are used to fill in the far northern latitudes of the map from about 75 degrees north latitude to the north pole. Coverage also improves farther south on the side of the moon facing away from Saturn. That improved coverage starts at about 40 degrees north latitude and stretches north to the pole in the area roughly west of the large Odysseus Crater (between 160 degrees and 260 degrees west longitude).

The map is an equidistant (simple cylindrical) projection and has a scale of 293 meters (960 feet) per pixel at the equator in the full size version. The mean radius of Tethys used for projection of this map is 536.3 kilometers (333.2 miles). The resolution of the map is 32 pixels per degree.

Photo credit: NASA/JPL/Space Science Institute

Note: For the polar views, click here for the northern hemisphere and here for the southern hemisphere.

Damascus Sulcus Hot Spot

Data from NASA's Cassini spacecraft have enabled scientists to make the highest-resolution heat intensity maps yet for the hottest part of a "tiger stripe" fissure on Saturn's moon Enceladus. The moon's south polar region features several of these long fissures that spray water and icy particles, and the one in this image is called Damascus Sulcus.

The thermal infrared data, shown in color, come from Cassini's composite infrared spectrometer (CIRS). The grayscale background image, which is illuminated by light reflected from Saturn rather than by direct sunlight, is from Cassini's high-resolution imaging camera (ISS). The CIRS scan gives scientists confidence that the peak temperature along Damascus Sulcus, the most active tiger stripe, was about 190 Kelvin (minus 120 degrees Fahrenheit). This temperature is slightly higher than the previous maximum temperatures measured by CIRS at Damascus, which were around 170 Kelvin (minus 150 degrees Fahrenheit).

The intensity of heat radiation, measured by CIRS at wavelengths from 7 to 9 microns, is color-coded, with blue, purple, red, orange and yellow denoting progressively more intense radiation, due to higher temperatures and/or larger expanses of warm material. The image is centered near 80 degrees South latitude and 315 degrees West longitude, and covers a region about 16 kilometers (10 miles) wide. The smallest details seen in the CIRS overlay are about 800 meters (0.5 miles) in size.

The region of peak temperature is sharply bounded by the sides of the trench. Thanks to its high resolution, the CIRS map also shows for the first time that the regions on either side of the central trench are also radiating heat (shown as blue strips flanking the central multicolored strip in this image). CIRS measured temperatures of about 120 Kelvin (minus 240 degrees Fahrenheit) in the flanking regions about 400 to 1,200 meters (a quarter to three-quarters of a mile) away from the central trench.

These data were obtained on August 13, 2010 as the south pole of Enceladus began to go into winter darkness.

Photo credit: NASA/JPL/GSFC/SWRI/SSI

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

Enceladus Tiger Stripe Hot Spots

This image shows a high-resolution heat intensity map of part of the south polar region of Saturn's moon Enceladus, made from data obtained by NASA's Cassini spacecraft.

The map reveals never-before-seen details of warm fractures that branch off like split ends from the ends of the main trenches of two "tiger stripes." The features nicknamed "tiger stripes" are long fissures that spray water vapor and icy particles. These two fissures, Cairo Sulcus (left) and Alexandria Sulcus (right), extend to the lower right, off the bottom of the image. The map also shows an intriguing isolated warm spot, shown in purple-red in the upper left of the image, that is separated from other active fissures.

The thermal data came from Cassini's composite infrared spectrometer during an August 13, 2010, flyby of Enceladus. Scientists overlaid the data on a background map of that region made from Cassini images taken in July 2005. The intensity of thermal radiation, measured at wavelengths from 12 to 16 microns, is color-coded, with dark blue, purple, red and orange denoting progressively more intense radiation, due to higher temperatures and/or larger expanses of warm material. The pale blue color indicates regions that were mapped but that were too cold to emit significant radiation. Alignment of the thermal map with the underlying base map is approximate. The map shows a region approximately 130 kilometers (80 miles) across.

These data were obtained as winter darkness began to engulf the south polar region of Enceladus. Away from the warm tiger stripes, which reach temperatures up to 190 Kelvin (minus 120 degrees Fahrenheit), Cassini measured surface temperatures near Enceladus' south pole as low as 52 Kelvin (minus 365 degrees Fahrenheit), and still colder temperatures are expected as winter advances. Scientists are still analyzing the data to calculate a temperature for the cross-cutting fractures and the isolated warm spot.

Image credit: NASA/JPL/GSFC/SWRI/SSI

Looming Enceladus

Small water ice particles fly from fissures in the south polar region of Saturn's moon Enceladus in this image taken during the August 13, 2010, flyby of the moon by NASA's Cassini spacecraft.

This view looks toward the night side of Saturn, which is in the lower left of the image. Enceladus, in the top right, is closer to the spacecraft than the planet is in this view. Sunlight scatters through the planet's atmosphere and forms the bright diagonal line running from the left to bottom right of the image. The atmosphere appears layered here. Scientists think the different layers on the limb are real and not an artifact of the camera's exposure.

The famous jets, imaged by Cassini's cameras for the first time in 2005, are faintly seen here erupting from the fractures that cross the south polar region of the moon.

Illuminated terrain seen on Enceladus is on the leading hemisphere of the moon, or the side facing forward in the moon's orbit around Saturn. North on Enceladus (504 kilometers, 313 miles across) is up. The jets appear faint here, but can be seen near the center of the image. See PIA11688 to learn more.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was obtained at a distance of approximately 59,000 kilometers (37,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 155 degrees. Image scale on Enceladus is 353 meters (1,157 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Enceladus Before Saturn's Limb

Jets of water ice particles spew from Saturn's moon Enceladus in this image obtained by NASA's Cassini spacecraft on August 13, 2010. A crescent of the moon appears dimly illuminated in front of the bright limb of Saturn.

This view looks toward the night side of Saturn, which occupies the lower half of the image. Enceladus, in the center of the image, is closer to the spacecraft than the planet is in this view. Sunlight scatters through the planet's atmosphere and forms the bright diagonal line running from the left to right of the image. Lit terrain seen on Enceladus (504 kilometers, 313 miles across) is on the leading hemisphere of the moon. North on Enceladus is up.

The jets erupting from the south polar region appear faint here, but can be seen at the bottom of the crescent of the moon. See PIA11688 to learn more.

The image was taken in visible light with the Cassini spacecraft wide-angle camera. The view was acquired at a distance of approximately 61,000 kilometers (38,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 155 degrees. Image scale is 4 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute