Mysterious Iapetus
May 12, 2006

A distant glimpse of Iapetus reveals details within the dark terrain of Cassini Regio, including an impact basin at top that is roughly 400 kilometers (250 miles) wide.
Researchers remain unsure about the mechanism that has darkened the leading hemisphere.

This view looks toward the southern hemisphere on the leading side of Iapetus (1,468 kilometers, or 912 miles across). North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 4, 2006, at a distance of approximately 1.4 million kilometers (900,000 miles) from Iapetus. The image scale is 9 kilometers (6 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

From Dark to Bright and Red to White
May 22, 2006

Cassini's landmark investigation of Saturn's yin-yang moon Iapetus, with its bright and dark hemispheres, continues to provide insights into the nature of this intriguing body.
These two views of Iapetus primarily show terrain in the southern part of the moon's dark leading hemisphere -- the side of Iapetus that is coated with dark material. The bright south pole of Iapetus is visible, along with some terrain (at the bottom) that lies on the bright trailing hemisphere.

The dark terrain known as Cassini Regio is uniformly dark between the equator and about 30 degrees south latitude. From there down to about 50 to 60 degrees south latitude, the dark material looks "patchy" because south-facing crater walls are bright (being largely devoid of the dark material). South of this region, only some northward-facing crater walls are still dark, while the bright terrain has a somewhat reddish color.

Beyond 90 degrees south (i.e., on the trailing side), the reddish color becomes white. The region at the bottom of the color view presented here shows this "color boundary" in the bright terrain, which also marks the boundary between the leading and trailing hemispheres.

Iapetus is 1,468 kilometers (912 miles) across. North is up in the monochrome image and rotated 16 degrees to the left in the color image.

The monochrome image on the left was taken using a filter sensitive to wavelengths of infrared light centered at 930 nanometers. The image was obtained with the Cassini spacecraft narrow-angle camera on April 8, 2006, at a distance of approximately 866,000 kilometers (538,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 88 degrees. The image scale is 5 kilometers (3 miles) per pixel.

The color view on the right was created by combining images taken in ultraviolet, green and infrared spectral filters. The images were acquired with the Cassini spacecraft narrow-angle camera on April 9, 2006, at a distance of approximately 692,000 kilometers (430,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 101 degrees. The image scale is 4 kilometers (2.5 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

World of Contrast
August 2, 2006

This Cassini spacecraft view shows how the bright and dark regions on Iapetus fit together like the seams of a baseball. Some of the material that covers the moon's dark, leading side spills over into regions on the brighter trailing side, creating the feature near upper right referred to by some scientists as "the Moat."
(See Iapetus by Saturn Shine for a higher resolution view of this region.)

The large impact basin above center in the dark terrain has a diameter of about 550 kilometers (340 miles).

This view looks toward the Saturn-facing hemisphere of Iapetus (1,468 kilometers, or 912 miles across). North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 25, 2006 at a distance of approximately 1.6 million kilometers (1 million miles) from Iapetus. Image scale is 9 kilometers (6 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Duotone Moon
September 25, 2006

The many impact scars borne by Iapetus are made far more conspicuous in the region of transition from its dark hemisphere to its bright one. In this terrain, the dark material that coats Cassini Regio accentuates slopes and crater floors, creating a land of stark contrasts.
North on Iapetus (1,468 kilometers, or 912 miles across) is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 6, 2006 at a distance of approximately 2.2 million kilometers (1.4 million miles) from Iapetus and at a Sun- Iapetus-spacecraft, or phase, angle of 26 degrees. Image scale is 13 kilometers (8 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Brightside in View
January 5, 2007

The Cassini spacecraft continues to image terrain on Iapetus that is progressively eastward of the terrain it has previously seen illuminated by sunlight.

The region seen here was imaged in reflected light from Saturn at excellent resolution in the close flyby on New Year's Eve 2004 (see Iapetus by Saturn Shine).

This view looks toward the equator of Iapetus (1,468 kilometers, or 912 miles across) on the moon's Saturn-facing side. North is up and rotated 11 degrees to the right.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on Nov. 27, 2006 at a distance of approximately 2 million kilometers (1.2 million miles) from Iapetus. Image scale is 12 kilometers (7 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA\'s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Cloaking Iapetus
March 22, 2007

Darkness sweeps over Iapetus as the Cassini spacecraft watches the shadow of Saturn's B ring engulf the dichotomous moon. The image at left shows the unshaded moon, while at right, Iapetus sits in the shadow of the densest of Saturn's rings.

North on Iapetus (1,468 kilometers, or 912 miles across) is up and rotated eight degrees to the left.

The images were taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 13, 2007 at a distance of approximately 2.3 million kilometers (1.4 million miles) from Iapetus. Image scale is 14 kilometers (8 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

On the Bright Side
May 29, 2007

The Cassini spacecraft views terrain on the bright, trailing side of Iapetus in natural color. This side of Iapetus starkly contrasts with the much darker leading hemisphere, and some of the dark material seen here in association with craters near the terminator is an extension of the leading hemisphere terrain.

This region was previously imaged by the spacecraft at a much finer resolution -- a spatial scale of less than 1 kilometer (0.6 miles) per pixel -- during a flyby at the close of 2004. This terrain was then on the moon's night side at the time, and Cassini imaged it using weak, reflected light from Saturn (see Iapetus by Saturn Shine).

The present view looks toward Iapetus (1,468 kilometers, or 912 miles across) from about 24 degrees above the moon's equator.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were taken with the Cassini spacecraft narrow-angle camera on April 15, 2007 at a distance of approximately 2.3 million kilometers (1.4 million miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 66 degrees. Scale in the original images is 13 kilometers (8 miles) per pixel. The view has been magnified by a factor of three.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

July 17, 2007
(Source: Jet Propulsion Laboratory)

Saturn's distinctive moon Iapetus (eye-APP-eh-tuss) is cryogenically frozen in the equivalent of its teenage years. The moon has retained the youthful figure and bulging waistline it sported more than three billion years ago, scientists report.

"Iapetus spun fast, froze young, and left behind a body with lasting curves," said Julie Castillo, Cassini scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.


Unlike any other moon in the solar system,
Iapetus is the same shape today as it was when
it was just a few hundred million years old.

Unlike any other moon in the solar system, Iapetus is the same shape today as it was when it was just a few hundred million years old; a well-preserved relic from the time when the solar system was young. These results appear in the online version of the journal Icarus.

Cassini flew by Iapetus in early 2005 and discovered the moon had a walnut shape, bulging at its midsection. On top of that it has a chain of mountains located exactly along its equator.

Scientists now think the moon's bulging midriff and slow spin rate point to heating from long-extinct radioactive elements present when the solar system was born.

"We've modeled how Iapetus formed its big, spin-generated bulge and why its rotation slowed down to its present nearly 80-day period. As an unexpected bonus, Iapetus also told us how old it was," said Dennis Matson, Cassini project scientist at JPL. "You would expect a very fast-spinning moon to have this bulge, but not a slow-spinning moon, because the bulge would have been much flatter."

Scientists calculate Iapetus originally rotated much faster -- at least five hours, but less than 16 hours per revolution. The fast spin gave the moon an oblate shape that increased the surface area (in the same way the surface area of a round balloon stretches when the balloon is pressed into an oblate shape). By the time the rotation slowed down to a period of 16 hours, the outer shell of the moon had frozen. Furthermore, the surface area of the cold moon was now smaller. The excess surface material was too rigid to go back smoothly into the moon. Instead, it piled up in a chain of mountains at the equator.

"Iapetus' development literally stopped in its tracks," said Castillo. "In order for tidal forces to slow Iapetus to its current spin rate, its interior had to be much warmer, close to the melting point for water ice." The challenge in developing a model of how Iapetus came to be "frozen in time" has been in deducing how it ever became warm enough to form a bulge in the first place, and figuring out what caused the heat source to turn off, leaving Iapetus to freeze.

The heat source had to have a limited life span, to allow the moon's crust to rapidly become cold and retain its immature shape. After looking at several models, scientists concluded that the heat came from its rocks, which contain short-lived radioactive isotopes aluminum-26 and iron-60 (which decay very rapidly on a geologic timescale). Since these elements decay at a known rate, this allowed scientists to "carbon date" Iapetus by using aluminum-26 instead of carbon. Scientists calculate the age of Iapetus to be roughly 4.564 billion years old.

Evidence for these same isotopes (aluminum-26 and iron-60) has been found in meteorites formed in the inner solar system. Therefore, there is a possibility of comparing the early chronology of the outer solar system with other objects in the inner solar system, such as Earth, Earth's moon and asteroids.

"This is the first direct evidence of the early spin history for a satellite in the outer solar system. It teaches us more about how the speed of a body's rotation influenced its evolution, and broadens our knowledge of the early history of outer planet satellites," said Matson.

Cassini's next close encounter with Iapetus will occur on Sept. 10, 2007, at 1,000 kilometers (620 miles) from the surface.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington.

More information on the Cassini mission is available at: http://www.nasa.gov/cassini.

Contacts:
Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.


NEWS RELEASE: 2007-079

Source: NASA/JPL - Cassini - Press Release

Unveiling Iapetus
August 21, 2007

As the Cassini spacecraft sets up for its September 2007 close encounter with the two-toned moon Iapetus, the spacecraft is seeing more of the moon's bright, trailing hemisphere. This is a region Cassini has seen relatively little of until recently. The September encounter will provide high resolution images of this region, including the large crater seen here at about the five o'clock position.

North on Iapetus (1,468 kilometers, or 912 miles across) is up and rotated about 5 degrees to the right.

The image was taken using a spectral filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The view was acquired with the Cassini spacecraft narrow-angle camera on July 3, 2007. The view was acquired at a distance of approximately 2.2 million kilometers (1.4 million miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 53 degrees. Image scale is 13 kilometers (8 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

September 5, 2007
(Source: Jet Propulsion Laboratory)

PASADENA, Calif. - Cassini will make its only close flyby of Saturn's odd, two-toned, walnut-shaped moon Iapetus on Sept. 10, 2007, at about 1,640 kilometers (1,000 miles) from the surface.

This flyby will be 100 times closer than Cassini's 2004 encounter, and will be the last time the spacecraft will aim its instruments at this moon.


Images taken with Cassini's ultraviolet imaging
spectrograph shed some light on the dark side
of Saturn's moon Iapetus. Scientists are trying
to figure out what painted Iapetus' dark side.

--------------------------------------------------------------------------------

Iapetus (pronounced eye-APP-eh-tuss) has a ridge of surprisingly large mountains -- the so-called "belly-band" -- that lies directly on top of the equator. The moon also has a distinct difference in the brightness of its leading and trailing hemispheres, one as bright as snow and the other dark as tar. The irregular shape, the mountain ridge and Iapetus' brightness contrast are among the key mysteries scientists are trying to solve.

There are several different ideas on the origin of the dark material. Is it from inside or outside of Iapetus? Is it residue from some other moon or moons? Is it due to impacts by meteoroids or comet debris?

"We are on the search for the brush that may have painted Iapetus's dark side," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.


This map of the surface of Iapetus, generated
from images taken by NASA's Cassini and
Voyager spacecraft, illustrates the imaging
coverage planned for Cassini's very close
flyby of the two-toned moon on Sept. 10,
2007.

--------------------------------------------------------------------------------

"This dark stuff appears in several places in the Saturn system and might be present not just on Iapetus but many other moons," said JPL scientist Amanda Hendrix of Cassini's ultraviolet imaging spectrograph team and lead author of a paper soon to be published in the journal Icarus that explores the possible sources of the Iapetus dark material.

There's a reddish tint to the Iapetus dark stuff, an important clue in tracing its origin, she said. Saturn's moon Hyperion, which shows evidence of a violent disruption in its past, has a reddish tint, too. "It may be that the event that disrupted Hyperion deposited reddish material onto Iapetus," she said. "Hyperion may be the artist that's painting Iapetus dark."

Yet another Icarus paper on Iapetus by Dale Cruikshank at NASA's Ames Research Center, Moffett Field, Calif., and colleagues, reports that the dark material on Iapetus and Saturn's small moon Phoebe may be composed of the same complex, prebiotic hydrocarbons that appear to play a fundamental role in the origin of life. These chemicals, called polycyclic aromatic hydrocarbons, exist on objects ranging from backyard barbeques to comets, meteorites and the stardust that forms planets and flows between stars. They are important markers in studies of the origin of life in the universe.

An array of Cassini instruments will home in on Iapetus during the flyby. The full menu of objectives includes plans to: characterize the chemical composition of the surface; look for evidence of a faint atmosphere or erupting gas plumes; and map the nighttime temperature of the surface. This will be the first Cassini flyby of an icy moon, other than Titan, that's close enough and slow enough to perform radar imaging with Cassini's Synthetic Aperture Radar. A large swath of terrain will be covered, including the equatorial ridge and regions of craters and basins. These measurements may provide the height of some of the features.

"What is really neat is that we are doing radar of an icy object for which we actually have pictures," said Steve Ostro, a radar scientist at JPL. Until now, he said, the radar had been used to reveal the surface of cloud-covered Titan. Iapetus' surface is easily visible. "This will be a lesson on how to interpret radar images on an icy body. With Titan, because of the cloud cover, we don't know what we are looking at much of the time, but for Iapetus we will know very well," he said. In coming weeks, scientists will be analyzing data from multiple instruments. Some results of that analysis will be presented at a planetary science conference in Orlando, Fla., in mid-October.

More information on the Cassini-Huygens mission is available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.

Contacts:
Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

NEWS RELEASE: 2007-096

Source: NASA/JPL - Cassini - News Release

Exposing Iapetus' Dark Side
September 6, 2007

Images taken with Cassini's ultraviolet imaging spectrograph shed some light on the dark side of Saturn's moon Iapetus. Scientists are trying to figure out what painted Iapetus' dark side. This is one of the biggest mysteries scientists are trying to answer during the upcoming Sept. 10, 2007, flyby.

The ultraviolet image on the left indicates water ice abundance across the surface: the bright north polar terrain (shown in red) is the iciest region in this view. Away from the pole, as the color shifts to blue, less water ice is present in the surface. The darkest terrain, which includes very little water ice, is shown in light blue. The dark sky background viewed during the observation is shown as purple in this color scheme.

The ultraviolet-light image was taken during a flyby in December 2004. A visible light image taken on the same date is shown on the right for reference (see Encountering Iapetus).

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The ultraviolet imaging spectrograph was designed and built at, and the team is based at the University of Colorado, Boulder. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/home/index.cfm. The ultraviolet imaging spectrograph team home page is at http://lasp.colorado.edu/cassini. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/University of Colorado/Space Science Institute

Source: NASA/JPL - Cassini

Eyes on Iapetus!
September 6, 2007

This map of the surface of Iapetus, generated from images taken by NASA's Cassini and Voyager spacecraft, illustrates the imaging coverage planned for Cassini's very close flyby of the two-toned moon on Sept. 10, 2007. This flyby will be Cassini's only close approach to Iapetus (1,468 kilometers, or 912 miles across) during the entire planned mission.

At closest approach, Cassini will be 1,640 kilometers (1,020 miles) above the surface of Iapetus. The spacecraft will pass the moon at a speed of about 2.4 kilometers (1.5 miles) per second--a relatively leisurely pace that will allow plenty of time for the scientific instruments on board to collect massive amounts of data.

Cassini's previous encounter with Iapetus, on Dec. 31, 2004, focused on the mysterious territory in Cassini Regio, the region blanketed by dark material that covers most of the moon's leading hemisphere. The upcoming encounter will be primarily concerned with terrain farther west, in the important transition region between Cassini Regio and the bright trailing hemisphere. Scientists hope to learn a great deal more about the composition of the materials that compose the surface of Iapetus during this encounter.

Another area of focus is the large equatorial ridge that overlies the moon's equator (see Encountering Iapetus). The ridge reaches 20 kilometers (12 miles) high in some places and extends over 1,300 kilometers (808 miles) in length. No other moon in the solar system has a geological feature like this striking ridge. The tallest mountains on the ridge rival Olympus Mons on Mars, which is approximately three times the height of Mt. Everest. Such giant mountains are a surprising feature for such a small body as Iapetus, which is nearly five times smaller than Mars and nearly nine times smaller than Earth.

Colored lines on the map enclose regions that will be covered at different imaging scales as Cassini encounters Iapetus. The highest expected resolution of Cassini images from this flyby is about 20 meters (65 feet) per pixel--significantly higher than the 2004 encounter.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Surface of Iapetus

09.11.07

This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn's moon Iapetus on September 10.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ Full resolution (117Kb)

Source: NASA - Missions - Cassini

Saturn's Moon Iapetus

09.11.07

This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn's moon Iapetus on September 10.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ Full resolution (159Kb)

Source: NASA - Missions - Cassini

Cassini Mission Status: Cassini Flies by Walnut-Shaped Moon Iapetus

Cassini completed its closest flyby of the odd moon Iapetus on Sept. 10, 2007. The spacecraft flew about 1,640 kilometers (1,000 miles) from Iapetus' surface and is returning amazing views of the bizarre moon.


Image above: Saturn's moon Iapetus.
Image credit: NASA/JPL/Space Science Institute
+ Full image and caption

All the data were successfully recorded on the spacecraft. Twenty-one minutes into the first post-flyby data downlink, the spacecraft went into a precautionary condition called safe mode. The cause has been determined to be a solid state power switch that was tripped due to a galactic cosmic ray hit.

While in safe mode, the spacecraft turns off all unnecessary activities and transmits only essential engineering telemetry at a low data rate, while it awaits commands from Earth.


Image above: Saturn's moon Iapetus.
Image credit: NASA/JPL/Space Science Institute
+ Full image and caption

Tuesday morning, Sept. 11, commands were sent to the spacecraft to resume high rate science and engineering data playback. The project expects all data on the spacecraft will be returned to Earth during downlinks on Tuesday and Wednesday, with no impact on the Iapetus science data return beyond a brief delay.

Due to the safing event, the sequence executing on the spacecraft was halted, and Cassini's instruments will not be turned back on for three or four days. The last time Cassini was in safe mode was over four years ago.

Media contact: Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Source: NASA - Missions - Cassini - Media

Close-Up of Iapetus

09.11.07

This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn's moon Iapetus on September 10.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ Full resolution (272Kb)

Source: NASA - Missions - Cassini

Close-Up of Iapetus

09.12.07

This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn's moon Iapetus on September 10.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ Full resolution

Source: NASA - Missions - Cassini

Close-Up of Iapetus

09.12.07

This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn's moon Iapetus on September 10.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ Full resolution

Source: NASA - Missions - Cassini

Close-Up of Iapetus

09.12.07

This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn's moon Iapetus on September 10.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

Source: NASA - Missions - Cassini

The Himalayas of Iapetus
September 12, 2007

This stunning close-up view shows mountainous terrain that reaches about 10 kilometers (6 miles) high along the unique equatorial ridge of Iapetus. The view was acquired during Cassini's only close flyby of the two-toned Saturn moon.

Above the middle of the image can be seen a place where an impact has exposed the bright ice beneath the dark overlying material.

The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 3,870 kilometers (2,400 miles) from Iapetus. Image scale is 23 meters (75 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Inky Stains on a Frozen Moon
September 12, 2007

Dark material splatters the walls and floors of craters in the surreal, frozen wastelands of Iapetus. This image shows terrain in the transition region between the moon's dark leading hemisphere and its bright trailing hemisphere. The view was acquired during Cassini's only close flyby of the two-toned Saturn moon.

The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 6,030 kilometers (3,750 miles) from Iapetus. Image scale is 36 meters (118 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Saturn's Moon Iapetus Is the Yin-and-Yang of the Solar System

PASADENA, Calif. - Scientists on the Cassini mission to Saturn are poring through hundreds of images returned from the Sept. 10 flyby of Saturn's two-toned moon Iapetus. Pictures returned late Tuesday and early Wednesday show the moon's yin and yang--a white hemisphere resembling snow, and the other as black as tar.

Images show a surface that is heavily cratered, along with the mountain ridge that runs along the moon's equator. Many of the close-up observations focused on studying the strange 20-kilometer high (12 mile) mountain ridge that gives the moon a walnut-shaped appearance.


Image above: Cassini surveys a bright landscape coated by dark material
on Iapetus. This image shows terrain in the transition region between the
moon’s dark leading hemisphere and its bright trailing hemisphere.
Image credit: NASA/JPL/Space Science Institute

"The images are really stunning," said Tilmann Denk, Cassini imaging scientist at the Free University in Berlin, Germany, who was responsible for the imaging observation planning. "Every new picture contained its own charm. I was most pleased about the images showing huge mountains rising over the horizon. I knew about this scenic viewing opportunity for more than seven years, and now the real images suddenly materialized."

This flyby was nearly 100 times closer to Iapetus than Cassini's 2004 flyby, bringing the spacecraft to about 1,640 kilometers (1,000 miles) from the surface. The moon's irregular walnut shape, the mountain ridge that lies almost directly on the equator and Iapetus' brightness contrast are among the key mysteries scientists are trying to solve.

"There's never a dull moment on this mission," said Bob Mitchell, Cassini program manager, NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are very excited about the stunning images being returned. There's plenty here to keep many scientists busy for many years."

"Our flight over the surface of Iapetus was like a non-stop free fall, down the rabbit hole, directly into Wonderland! Very few places in our solar system are more bizarre than the patchwork of pitch dark and snowy bright we've seen on this moon," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colo.


Image above: This stunning close-up view
shows mountainous terrain that reaches about
10 kilometers (6 miles) high along the unique
equatorial ridge of Iapetus.
Image credit: NASA/JPL/Space Science Institute

The return of images and other data was delayed early Tuesday due to a galactic cosmic ray hit which put the spacecraft into a precautionary state called safe mode. This occurred after the spacecraft had placed all of the flyby data on its data recorders and during the first few minutes after it began sending the data home. The data flow resumed later that day and concluded on Wednesday. The spacecraft is operating normally and its instruments are expected to return to normal operations in a few days.

"Iapetus provides us a window back in time, to the formation of the planets over four billion years ago. Since then its icy crust has been cold and stiff, preserving this ancient surface for our study," said Torrence Johnson, Cassini imaging team member at JPL.

Cassini's multiple observations of Iapetus will help to characterize the chemical composition of the surface; look for evidence of a faint atmosphere or erupting gas plumes; and map the nighttime temperature of the surface. These and other results will be analyzed in the weeks to come.

Iapetus flyby images are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and and http://ciclops.org.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Media contact: Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

Preston Dyches 720-974-5859
Space Science Institute, Boulder, Colo.
media@ciclops.org

2007-101

Source: NASA - Missions - Cassini - Media

Coated Craters

09.12.07

Cassini surveys a bright landscape coated by dark material on Iapetus. This image shows terrain in the transition region between the moon’s dark leading hemisphere and its bright trailing hemisphere. The view was acquired during Cassini's only close flyby of the two-toned Saturn moon.

The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 5,260 kilometers (3,270 miles) from Iapetus. Image scale is 32 meters (105 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ High resolution

Source: NASA - Missions - Cassini

The "Voyager" Mountains

09.12.07

Cassini zooms in, for the first time, on the patchy, bright and dark mountains originally identified in images from the NASA Voyager spacecraft taken more than 25 years earlier. The image was acquired during Cassini's only close flyby of Iapetus, a two-toned moon of Saturn.

The terrain seen here is located on the equator of Iapetus at approximately 199 degrees west longitude, in the transition region between the moon's bright and dark hemispheres. North is up.

The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 9,240 kilometers (5,740 miles) from Iapetus. Image scale is 55 meters (180 feet) per pixell.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: Image credit: NASA/JPL/Space Science Institute

+ High resolution

Source: NASA - Missions - Cassini

Cassini Is on the Trail of a Runaway Mystery

10.08.07

NASA scientists are on the trail of Iapetus' mysterious dark side, which seems to be home to a bizarre "runaway" process that is transporting vaporized water ice from the dark areas to the white areas of the Saturnian moon.

This "thermal segregation" model may explain many details of the moon's strange and dramatically two-toned appearance, which have been revealed exquisitely in images collected during a recent close flyby of Iapetus by NASA's Cassini spacecraft.


Image above: Cassini captures the first high-resolution glimpse of the
bright trailing hemisphere of Saturn's moon Iapetus in this false-color
mosaic. This false-color mosaic shows the entire hemisphere of Iapetus.
Image credit: NASA/JPL/Space Science Institute

Infrared observations from the flyby confirm that the dark material is warm enough (approximately minus 230 degrees Fahrenheit or 127 Kelvin) for very slow release of water vapor from water ice, and this process is probably a major factor in determining the distinct brightness boundaries.

"The side of Iapetus that faces forward in its orbit around Saturn is being darkened by some mysterious process," said John Spencer, Cassini scientist with the composite infrared spectrometer team from the Southwest Research Institute, Boulder, Colo.

Using multiple instruments on Cassini, scientists are piecing together a complex story to explain the bright and dark faces of Iapetus. But yet to be fully understood is where the dark material is coming from. Is it native or from outside the moon? It has long been hypothesized that this material did not originate from within Iapetus, but instead was derived from other moons orbiting at a much greater distance from Saturn in a direction opposite to Iapetus.

Scientists are now converging on the notion that the darkening process in fact began in this manner, and that thermal effects subsequently enhanced the contrast to what we see today.


Image above: This image compares midday
temperatures on Saturn's moon Iapetus,
recorded by the composite infrared spectrometer
instrument during Cassini's close Sept. 10, 2007
flyby, with images of the same region recorded
during the same flyby by the Cassini imaging
science subsystem.
Image credit: NASA/JPL/GSFC/SwRI/SSI

"It's interesting to ponder that a more than 30-year-old idea might still help explain the brightness difference on Iapetus," said Tilmann Denk, Cassini imaging scientist at the Free University in Berlin, Germany. "Dusty material spiraling in from outer moons hits Iapetus head-on, and causes the forward-facing side of Iapetus to look different than the rest of the moon."

Once the leading side is even slightly dark, thermal segregation can proceed rapidly. A dark surface will absorb more sunlight and warm up, explains Spencer, so the water ice on the surface evaporates. The water vapor then condenses on the nearest cold spot, which could be Iapetus's poles, and possibly bright, icy areas at lower latitudes on the side of the moon facing in the opposite direction of its orbit. So the dark stuff loses its surface ice and gets darker, and the bright stuff accumulates ice and gets brighter, in a runaway process.

Scientists say the result is that there are virtually no shades of gray on Iapetus. There is only white and very dark.

Ultraviolet data also show a non-ice component in the bright, white regions of Iapetus. Spectroscopic analysis will reveal whether the composition of the material on the dark hemisphere is the same as the dark material that is present within the bright terrain.

"The ultraviolet data tell us a lot about where the water ice is and where the non-water ice stuff is. At first glance, the two populations do not appear to be present in the pattern we expected, which is very interesting," said Amanda Hendrix, Cassini scientist on the ultraviolet imaging spectrograph team at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Because of the presence of very small craters that excavate the bright ice beneath, scientists also believe that the dark material is thin, a result consistent with previous Cassini radar results. But some local areas may be thicker. The dark material seems to lie on top of the bright region, consistent with the idea that it is a residual left behind by the sublimated water ice.

Some other mysteries are coming together. There are more data on the signature mountain ridge that gives Iapetus its "walnut" appearance. In some places it appears subdued. One big question that remains is why it does not go all the way around. Was it partially destroyed after it formed, or did it never extend all the way around the moon? Scientists have ruled out that it is a youthful feature because it is pitted with craters, indicating it is old. And the ridge looks too solid and competent to be the result of an equatorial ring around the moon collapsing onto its surface. The ring theory cannot explain features that look like tectonic structures in the new high resolution images.

Over the next few months, scientists hope to learn more about Iapetus' mysteries.

New Iapetus images, temperature maps and other visuals on Iapetus are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C.


Media contact: Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

2007-113

Source: NASA - Missions - Cassini - Media

Approaching Iapetus
October 8, 2007

The slim crescent of Iapetus looms before the Cassini spacecraft as it approaches the mysterious moon.

Iapetus, 1,468 kilometers (912 miles) across, seen here in false color, is unique in its dramatic variation in brightness between the northern polar region and the middle and low latitudes. Equally prominent is the moon's equatorial ridge of towering mountains. The profile of the ridge against the darkness of space reveals that it is topped by a cratered plateau approximately 15 kilometers (9 miles) wide. Further west, the profile of the ridge changes from a long plateau to discrete peaks.

The mosaic consists of four image footprints across the surface of Iapetus and has a resolution of 489 meters (0.3 miles) per pixel.

A full-resolution clear filter image was combined with half-resolution images taken with infrared, green and ultraviolet spectral filters (centered at 752, 568 and 338 nanometers, respectively) to create this full-resolution false color mosaic.

The color seen in this view represents an expansion of the wavelength region of the electromagnetic spectrum visible to human eyes. The intense reddish-brown hue of the dark material is far less pronounced in true color images. The use of enhanced color makes the reddish character of the dark material more visible than it would be to the naked eye. In addition, the scene has been brightened to improve the visibility of surface features.

This view was acquired with the Cassini spacecraft narrow-angle camera on Sept. 10, 2007, at a distance of about 83,000 kilometers (51,600 miles) from Iapetus.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

A Scene of Craters
October 8, 2007

This high-resolution view shows a vast range of crater sizes in the dark terrain of the leading hemisphere of Saturn's moon Iapetus.

Across the scene, a few small bright spots indicate fresh, rayed craters where impactors have punched through the thin blanket of dark material to the cleaner ice beneath.

The slight elevation on the bottom half of the image is part of the giant equatorial ridge that spans a wide fraction of Iapetus' circumference. The numerous craters on top of the ridge indicate that it is an old surface feature.

The mosaic consists of three image footprints across the surface of Iapetus. The view is centered on terrain near 0.5 degrees north latitude, 141.6 degrees west longitude. Image scale is approximately 22 meters (72 feet) per pixel. Illumination is from the left.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft narrow-angle camera on Sept. 10, 2007, at a distance of approximately 63,000 kilometers (39,000 miles) from Iapetus and at a sun-Iapetus-spacecraft, or phase, angle of about 125 degrees.

Iapetus is 1,468 kilometers (912 miles) across.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Closest View of Iapetus
October 8, 2007

This mosaic of Cassini images shows the smallest details ever observed on Saturn's moon Iapetus.

Visible here are small craters as well as the base of a large mountain ridge located just south of the mosaic. At several places, bright spots about 20 to 50 meters (66 to 164 feet) across are visible. At these locations, more recent impactors have punched through the overlying blanket of dark material to reveal brighter, cleaner ice beneath.

Since the bright craters are relatively small and very shallow, it is likely that the dark blanket is rather thin in this area; it is assumed that its actual average thickness might be on the order of a foot.

The small crater at the upper left edge of the mosaic has a diameter of about 50 meters (164 feet) and shows a distinct ray pattern from excavated ice. This feature is so bright in comparison to the dark surrounding terrain that it had to be darkened manually so as not to look overexposed in this mosaic.

The mosaic consists of eight image footprints across the surface of Iapetus, presented here in simple cylindrical projection. The view is centered on terrain near 0 degrees north latitude, 164.9 degrees west longitude, within the dark leading hemisphere of Iapetus. Image scale is approximately 10 meters (33 feet) per pixel.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft narrow-angle camera on Sept. 10, 2007, at distances ranging from 1,627 to 2,040 kilometers (1,011 to 1,268 miles) from Iapetus. Iapetus is 1,468 kilometers (912 miles) across.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Towering Peaks of Iapetus
October 8, 2007

This stereo image, or anaglyph, shows huge mountains on Saturn's moon Iapetus, imaged by NASA's Cassini spacecraft during its very close flyby in Sept. 2007. These mountains are located at the moon's equator in the westward-most part of the dark terrain.

Here, the brightness pattern on the surface is very complex. The mountain in the center of this view is part of the range informally named "the Voyager mountains" that were first detected on the limb of the moon in NASA Voyager spacecraft images. Interestingly, its eastern (right) flank is dark, while the other flanks are bright. This suggests that external material arriving on Iapetus from its orbital motion might play a role in the darkening process. One plausible source, the outer moons of Saturn, might provide a very thin but steady stream of very dark particles from the eastern direction as seen from this mountain.

The mosaic consists of six image footprints across the surface of Iapetus. The view is centered on terrain near 0.1 degree north latitude, 199 degrees west longitude. Image scale is approximately 46 meters (151 feet) per pixel.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft narrow- angle camera on Sept. 10, 2007. Distances for the blue portion of the image range from 7,744 to 9,135 kilometers (4,812 to 5,676 miles) from Iapetus; distances for the red portion of the image range from 20,267 to 21,595 kilometers (12,593 to 13,418 miles) from the moon.

A separate, non-stereo version of the scene is included for comparison.

Iapetus is 1,468 kilometers (912 miles) across.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

The Transition Zone
October 8, 2007

Soaring above the alien, icy wastelands of Saturn's moon Iapetus, NASA's Cassini spacecraft captured a series of high-resolution images of the transition region from dark to bright terrain at southern middle latitudes that have been mosaicked together in this view.

An important characteristic of the terrain in the boundary region is that the isolated bright patches are mainly found on slopes facing toward the bright trailing hemisphere or toward the south pole. The same polarity is found within the bright terrain, where the dark material can be seen at the bottom of craters and on equator-facing slopes. These indicate that thermal effects are at play in painting the surface of Iapetus, 1,468 kilometers (912 miles) across. The mosaic consists of eight image footprints across the surface of Iapetus. The view is centered on terrain near 38.6 degrees south latitude, 171.3 degrees west longitude. Image scale is approximately 52 meters (171 feet) per pixel.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft narrow- angle camera on Sept. 10, 2007, at a distance of approximately 5,000 kilometers (3,100 miles) from Iapetus.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

A Complex Transition
October 8, 2007

The transition region from Saturn's moon Iapetus' dark leading hemisphere to its bright trailing hemisphere is a complicated patchwork of craters and highlands, with low elevations filled in by dark material.

An explanation of the pattern visible here might be key to a full understanding of the bright/dark dichotomy on Iapetus, 1,468 kilometers (912 miles) across.

The view is centered on the equator and covers an area 711 kilometers wide by 417 kilometers tall (442 by 259 miles).

The giant equatorial ridge visible on the dark leading hemisphere is not present anymore in this region. Instead, large, isolated mountains more than 10 kilometers (6 miles) tall are spread along the equator. These mountains show bright western flanks, while the surrounding lowlands are generally dark.

The bright mountains at center right, surrounded by dark terrain, are also visible in the stereo view Towering Peaks of Iapetus. The region of Iapetus seen in this mosaic is also visible in the color full-disk mosaic The Other Side of Iapetus.

The mosaic is an orthographic projection consisting of 21 image footprints across the surface of Iapetus. The view is centered on terrain near 0.1 degree north latitude, 199 degrees west longitude, in the quadrant of Iapetus that faces away from Saturn. Image scale is approximately 83 meters (272 feet) per pixel. An orthographic view is most like the view seen by a distant observer looking through a telescope.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft narrow- angle camera on Sept. 10, 2007, at distances ranging from 13,857 to 21,846 kilometers (8,610 to 13,574 miles) from Iapetus.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Spotty Iapetus
October 8, 2007

At high resolution, terrain in the transition region between bright and dark hemispheres on Saturn's moon Iapetus reveals a spotty appearance reminiscent of a Dalmatian. The bright material on the frozen surface of Iapetus, 1,468 kilometers (912 miles) across, is water ice, and the dark material is likely carbonaceous in composition.

The dark material is preferentially found at the bottoms of craters. Bright water ice forms the "bed rock" on Iapetus, while the dark, presumably loose material apparently lies on top of the ice.

The terrain seen here is also visible in Speckled Surface, but it is viewed here at higher resolution.

The mosaic consists of two image footprints across the surface of Iapetus. The view is centered on terrain near 42 degrees south latitude and 209.3 degrees west longitude, on the anti-Saturn facing hemisphere. Image scale is approximately 32 meters (105 feet) per pixel.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft narrow- angle camera on Sept. 10, 2007, at distances ranging from 5,363 to 5,884 kilometers (3,332 to 3,656 miles) from Iapetus.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Speckled Surface
October 8, 2007

Dark material has coated the low-elevation terrain and the interiors of craters in the southern portions of the quadrant on Iapetus that faces away from Saturn. This is part of the boundary region separating the dark leading and bright trailing hemispheres. The dark coating is thought to be no more than a few tens of centimeters thick (10 centimeters equals 4 inches) and, as seen here, predominately appears on the northern-facing walls of craters in the south.

Farther south, the dark splotches are less numerous and appear almost absent at the highest latitudes (near the bottom of the frame). This is a strong indicator that thermal effects play a role in the darkening process of parts of Iapetus' surface: the colder the surface, the less common is the dark terrain. As on Earth, the higher latitudes on Iapetus receive less heating by sunlight.

At left, below center, the eastern rim of a great and ancient impact basin can be seen. With a diameter of almost 500 kilometers (310 miles), it is one of the largest impact structures on Iapetus, 1,468 kilometers (912 miles) across, and in the entire Saturn system.

This monochrome view shows terrain also seen in The Other Side of Iapetus but at higher resolution.

The mosaic consists of three narrow-angle camera footprints across the surface of Iapetus. This view is centered on terrain near 35.1 degrees south latitude, 218.5 degrees west longitude. Image scale is approximately 231 meters (758 feet) per pixel.

The clear spectral filter images in this mosaic were obtained with the Cassini spacecraft on Sept. 10, 2007, at a distance of approximately 40,000 kilometers (25,000 miles) from Iapetus and at a sun-Iapetus-spacecraft, or phase, angle of 31 degrees.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

The Other Side of Iapetus
October 8, 2007

Cassini captures the first high-resolution glimpse of the bright trailing hemisphere of Saturn's moon Iapetus.

This false-color mosaic shows the entire hemisphere of Iapetus (1,468 kilometers, or 912 miles across) visible from Cassini on the outbound leg of its encounter with the two-toned moon in Sept. 2007. The central longitude of the trailing hemisphere is 24 degrees to the left of the mosaic's center.

Also shown here is the complicated transition region between the dark leading and bright trailing hemispheres. This region, visible along the right side of the image, was observed in many of the images acquired by Cassini near closest approach during the encounter.

Revealed here for the first time in detail are the geologic structures that mark the trailing hemisphere. The region appears heavily cratered, particularly in the north and south polar regions. Near the top of the mosaic, numerous impact features visible in NASA Voyager 2 spacecraft images (acquired in 1981) are visible, including the craters Ogier and Charlemagne.

The most prominent topographic feature in this view, in the bottom half of the mosaic, is a 450-kilometer (280-mile) wide impact basin, one of at least nine such large basins on Iapetus. In fact, the basin overlaps an older, similar-sized impact basin to its southeast.

In many places, the dark material -- thought to be composed of nitrogen-bearing organic compounds called cyanides, hydrated minerals and other carbonaceous minerals -- appears to coat equator-facing slopes and crater floors. The distribution of this material and variations in the color of the bright material across the trailing hemisphere will be crucial clues to understanding the origin of Iapetus' peculiar bright-dark dual personality.

The view was acquired with the Cassini spacecraft narrow-angle camera on Sept. 10, 2007, at a distance of about 73,000 kilometers (45,000 miles) from Iapetus.

The color seen in this view represents an expansion of the wavelengths of the electromagnetic spectrum visible to human eyes. The intense reddish-brown hue of the dark material is far less pronounced in true color images. The use of enhanced color makes the reddish character of the dark material more visible than it would be to the naked eye.

This mosaic consists of 60 images covering 15 footprints across the surface of Iapetus. The view is an orthographic projection centered on 10.8 degrees south latitude, 246.5 degrees west longitude and has a resolution of 426 meters (0.26 miles) per pixel. An orthographic view is most like the view seen by a distant observer looking through a telescope.

At each footprint, a full resolution clear filter image was combined with half-resolution images taken with infrared, green and ultraviolet spectral filters (centered at 752, 568 and 338 nanometers, respectively) to create this full-resolution false color mosaic.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/Space Science Institute

Source: NASA/JPL - Cassini

Iapetus' Equatorial Region
October 8, 2007

Cassini made a close flyby of Saturn's moon Iapetus on Sept. 10, 2007, and the visual and infrared mapping spectrometer obtained these images during that event.

These two images show a higher resolution version of the equatorial region shown in Tiny Grains on Iapetus. The equatorial region includes the equatorial bulge which shows no differences in these compositions compared to surrounding regions.

The color image on the right shows the results of mapping for three components of Iapetus' surface: carbon dioxide that is trapped or adsorbed in the surface (red), water in the form of ice (green), and a newly-discovered effect due to trace amount of dark particles in the ice creating what scientists call Rayleigh scattering (blue). The Rayleigh scattering effect is the main reason why the Earth's sky appears blue.

There is a complex transition zone from the dark region, on the right, which is high in carbon dioxide, to the more ice-rich region on the left. Some crater floors are filled with carbon dioxide-rich dark material. As the ice becomes cleaner to the left, the small dark particles become more scattered and increase the Rayleigh scattering effect, again indicative of less than 2 percent dark sub-0.5-micron particles.

The visual and infrared mapping spectrometer is like a digital camera, but instead of using three colors, it makes images in 352 colors, or wavelengths, from the ultraviolet to the near-infrared. The many wavelengths produce a continuous spectrum in each pixel, and these spectra measure how light is absorbed by different materials. By analyzing the absorptions expressed in each pixel, a map of the composition at each location on the moon can be constructed.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Visual and Infrared Mapping Spectrometer team is based at the University of Arizona.

For more information about the Cassini-Huygens mission, visit: http://saturn.jpl.nasa.gov/home/index.cfm. The visual and infrared mapping spectrometer team home page is at: http://wwwvims.lpl.arizona.edu.

Credit: NASA/JPL/University of Arizona /USGS

Source: NASA/JPL - Cassini

Two Ultraviolet Views of Iapetus
October 8, 2007

The far left image shows the bright-dark boundary region on Saturn's moon Iapetus at far-ultraviolet wavelengths, viewed by Cassini's ultraviolet imaging spectrograph on Sept. 10, 2007.

These wavelengths represent reflected solar light and indicate where the surface is brightest and highest in water ice abundance. (Red indicates the brightest regions, purple the darkest.) The bright "Voyager Mountains", part of the equatorial ridge, are seen as bright spots against a dark background. The dark material that covers one hemisphere of Iapetus is indicated in purple and is seen on the right side of this image.

The middle image is a color composite: blue-green (longer ultraviolet wavelengths) indicates where the surface is bright and probably richest in water ice. Red (short ultraviolet wavelengths) indicates where the surface is low in water ice and relatively high in dirty material. The sky background is also bright at these wavelengths, making the limb, or edge, of Iapetus where the surface is dark indistinguishable from the sky background.

The image on the right, taken by the imaging science subsystem, is for reference, with the regions observed by Cassini¿s ultraviolet imaging spectrometer outlined in red.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The ultraviolet imaging spectrograph was designed and built at, and the team is based at the University of Colorado, Boulder. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/home/index.cfm. The ultraviolet imaging spectrograph team home page is at http://lasp.colorado.edu/cassini. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL/University of Colorado/Space Science Institute

Source: NASA/JPL - Cassini

Tiny Grains on Iapetus
October 8, 2007

Cassini made a close flyby of Saturn's moon Iapetus on Sept. 10, 2007, and the visual and infrared mapping spectrometer obtained these images showing surface composition and particle size.

The visual and infrared mapping spectrometer is like a digital camera, but instead of using three colors, it makes images in 352 colors, or wavelengths, from the ultraviolet to the near-infrared. The many wavelengths produce a continuous spectrum in each pixel, and these spectra measure how light is absorbed by different materials. By analyzing the absorptions expressed in each pixel, a map of the composition at each location on the moon can be constructed.

The left image in the figure shows the amount of reflected light at a wavelength of 1.75 microns in the infrared (green light seen by our eyes is 0.53 microns). The color image on the right shows the results of mapping for three components of Iapetus' surface: carbon dioxide that is trapped or adsorbed in the surface (red), water in the form of ice (green), and a newly-discovered effect due to trace amount of dark particles in the ice creating what scientists call Rayleigh scattering (blue). The Rayleigh scattering effect is the main reason why the Earth's sky appears blue.

The Rayleigh scattering effect on Iapetus provides evidence that tiny grains, less than the wavelength of visible light (less than 0.5 microns) have been embedded in the surface of Iapetus. The tiny grains must be well-separated for the Rayleigh effect to become prominent, so the abundance of particles must be less than about 2 percent. The Rayleigh scattering effect shows in all areas, although weakly in dark regions (the red carbon dioxide dominates the color image), and it appears stronger away from the equator. Investigating the trend from dark to bright areas, the Rayleigh effect changes with the amount of dark material in the ice, and becomes weaker as more dark material is added. This points to cleaner ice as one moves north or south from the equator and away from the dark leading side of the moon (toward the right in the image).

This provides additional evidence for an external source for the dark material coating Iapetus, and for ice transport away from the warm dark regions and equator to the cooler poles. The ice transport away from the equator increases the concentration of dark material there and reduces the Rayleigh effect. With the volatile transport from the dark warm regions, the strong carbon dioxide signature is a surprise because frozen carbon dioxide is more volatile than water ice. Therefore, the carbon dioxide must be trapped, making its presence stable in the warm equatorial region. The trapping mechanism is currently under study.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Visual and Infrared Mapping Spectrometer team is based at the University of Arizona.

For more information about the Cassini-Huygens mission, visit: http://saturn.jpl.nasa.gov/home/index.cfm. The visual and infrared mapping spectrometer team home page is at: http://wwwvims.lpl.arizona.edu.

Credit: NASA/JPL/University of Arizona /USGS

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