Iapetus

Iapetus

To the Relief of Iapetus

Encountering Iapetus

Approaching Iapetus

Unveiling Iapetus

The Himalayas of Iapetus

Waning Iapetus

Spotty Iapetus

The Iapetus Atlas

Eyes on Iapetus!

Exposing Iapetus Dark Side

Iapetus: A View from the Top

Giant Landslide on Iapetus

Tiny Grains on Iapetus

The Other Side of Iapetus

Two Ultraviolet Views of Iapetus

Iapetus Surface Composition

Closest View of Iapetus

Iapetus Thermal Radiation Image

Iapetus Temperature Map

Iapetus Spins and Tilts

Iapetus New Year Flyby

Iapetus Dark Side

Warm and Dry on Iapetus

Iapetus Temperature Variation Map

VIMS Iapetus Two Shooter

Dark-stained Iapetus

Map of Iapetus - May 2008

Iapetus by Saturn Shine

Iapetus: Light and Dark

Flight over Iapetus

Map of Iapetus - January 2008

VIMS Shows Iapetus Surface Composition

NASA Cassini spacecraft examines the rough dark-light dichotomy of the terrain on Saturn moon Iapetus. Lit terrain seen here is on the Saturn-facing side of Iapetus.

Darkness sweeps over Iapetus as the Cassini spacecraft watches the shadow of Saturn 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 rings

Iapetus shows off its puzzling light and dark terrain in this image captured by NASA Cassini spacecraft. Lit terrain seen here is on the Saturn-facing side of Iapetus.

The oblate shape of the moon Iapetus is particularly noticeable in this portrait; the two-toned surface of the moon Iapetus also stands out against the darkness of space in this image taken by NASA Cassini spacecraft.

Cassini bids farewell to Saturn's yin-and-yang moon, Iapetus. This image is from the last set of observations Cassini made of this world of striking contrasts. The spacecraft helped scientists better understand Iapetus, solving a centuries-old mystery of why it should be bright on one side and dark on the other. Cassini observations of Iapetus (914 mile or 1471 kilometers across) support the prevailing theory that led to the understanding that the dichotomy of the surface is due to a combination of infalling dust from outside of the moon followed by a migration of water ice from the darker (therefore warmer) areas to the cold, brighter surfaces. See PIA11690 for more details. This false-color view is a composite of individual frames obtained using filters sensitive to ultraviolet (centered at 338 nanometers), green (centered at 568 nanometers) and infrared light (centered at 930 nanometers). The view has been enhanced to accentuate subtle color differences and fine-scale surface features. This view looks toward the Saturn-facing hemisphere of Iapetus. North on Iapetus is up and rotated 12 degrees to the left. The view was acquired on May 30, 2017, at a distance of approximately 1.5 million miles (2.5 million kilometers) from Iapetus. Image scale is 9 miles (15 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21347

NASA Cassini spacecraft looks toward a crescent of Saturn dark and light moon, Iapetus.

NASA Cassini spacecraft looks toward a crescent of Saturn moon Iapetus and glimpses a bit of that moon yin-yang appearance.

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

A crescent Iapetus shows, at the top right of this image from NASA Cassini spacecraft, some of the dark terrain characterizing this unusual Saturnian moon.

This stereo view of Iapetus was created by combining two NASA Cassini images, which were taken one day apart. The view serves mainly to show the spherical shape of Iapetus and some of the moon’s topography. 3D glasses are necessary to view this image.

These two global images of Iapetus taken by NASA Cassini spacecraft show the extreme brightness dichotomy on the surface of this peculiar Saturnian moon.

NASA Cassini spacecraft takes one of its last good looks at Iapetus, a Saturnian moon known for its yin-yang-like, bright-and-dark color pattern.

A large dark region fills a semicircle of the visible disk of Iapetus on the left of this NASA Cassini spacecraft image, appearing like a bite taken out of this Saturnian moon.

Saturn outermost large moon, Iapetus, has a bright, heavily cratered icy terrain and a dark terrain, as shown in this NASA Voyager 2 image taken on Aug. 22, 1981. http://photojournal.jpl.nasa.gov/catalog/PIA00348

NASA Cassini spacecraft stared toward Saturn two-toned moon Iapetus for about a week in early 2015, in a campaign motivated in part to investigate subtle color differences within the moon bright terrain.

This global digital map of Saturn moon Iapetus was created using data taken during Cassini and Voyager spacecraft flybys. The map is an equidistant projection and has a scale of 641 meters 2,103 feet per pixel

This set of global, color mosaics of Saturn moon Iapetus was produced from images taken by NASA Cassini spacecraft during its first ten years exploring the Saturn system.

The two-toned surface of Saturn moon Iapetus is demonstrated in the dark region of the moon visible on the top left and the bright crater in the lower right of this portrait captured by NASA Cassini spacecraft.

While on final approach for its Sept. 2007 close encounter with Saturn moon Iapetus, NASA Cassini spacecraft spun around to take in a sweeping view of the Saturn System.

This false-color view taken by NASA Cassini spacecraft is one of a panel of three images of Saturn moon Iapetus showing the boundary of the global color dichotomy on the hemisphere of this moon facing away from Saturn.

This anaglyph, shows huge mountains on Saturn moon Iapetus, imaged by NASA Cassini spacecraft during its very close flyby in Sept. 2007. 3D glasses are necessary to view this image.

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 PIA10010. 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. http://photojournal.jpl.nasa.gov/catalog/PIA10011

Although it is no longer uncharted land, the origin of the dark territory of Cassini Regio on Iapetus remains a mystery. The view looks down onto the northern hemisphere of Iapetus and shows terrain on the moon leading hemisphere

The Cassini spacecraft views terrain on the bright, trailing side of Iapetus in natural color

The moon Iapetus, like the "force" in Star Wars, has both a light side and a dark side. Scientists think that Iapetus' (914 miles or 1471 kilometers across) dark/light asymmetry was actually created by material migrating away from the dark side. For a simulation of how scientists think the asymmetry formed, see Thermal Runaway Model . Lit terrain seen here is on the Saturn-facing hemisphere of Iapetus. North on Iapetus is up and rotated 43 degrees to the right. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Jan. 4, 2015. The view was acquired at a distance of approximately 2.5 million miles (4 million kilometers) from Iapetus. Image scale is 15 miles (24 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/pia18307

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

Some of Iapetus dark surface interrupts the moon lighter terrain in this view from NASA Cassini spacecraft.

Light and dark terrain covers the surface of Saturn moon Iapetus in this view from NASA Cassini spacecraft.

Iapetus is a moon of extreme contrasts. The light and dark features give the moon a distinctive yin and yang appearance in this image from NASA Cassini spacecraft.

With its light and dark surface, Iapetus appears almost like a yin and yang symbol or a comma punctuation mark in this Cassini spacecraft image.

Craters give a rugged look to surface of Iapetus, especially in the large basin of Engelier visible along the southern limb of the moon in this view captured by NASA Cassini spacecraft.

NASA Cassini Orbiter captures a far-off view of the two-toned surface of Saturn moon, Iapetus. Scientists continue to investigate the nature of this moon surface.

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 dark, leading side spills over into regions on the brighter trailing side

A large crater can be seen in the southern hemisphere of Saturn two-tone moon Iapetus. Lit terrain seen here is on the trailing hemisphere while the leading hemisphere is extremely dark and whose trailing hemisphere is as white as snow.

NASA Cassini Orbiter captures a far-off view of the two-toned surface of Saturn moon, Iapetus.

Iapetus is a world of contrast, with light and dark regions fitting together like cosmic puzzle pieces. Cassini Regio on Iapetus (914 miles or 1,471 kilometers across) is covered in a layer of dark, dusty material creating a stark contrast to the much brighter region that surrounds it. This leads to the moon's distinctive, two-toned appearance. This view looks toward Saturn-facing hemisphere of Iapetus. North on Iapetus is up and rotated 20 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 11, 2017. The view was obtained at a distance of approximately 1.6 million miles (2.6 million kilometers) from Iapetus. Image scale is 9 miles (15 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21332

Details in the Dark

In this terrain, the dark material that coats Cassini Regio accentuates slopes and crater floors, creating a land of stark contrasts

The Voyager Mountains

Speckled Surface

A Scene of Craters

Saturn Yin-Yang Moon

Distant Crescent

Seeing in the Dark

Inky Stains on a Frozen Moon

Saturn Two-Face Moon

Taking a Longer View

Coated Craters

A Complex Transition

The Transition Zone

Flyby Follow-up

Iapetan Geography

On October of 1997, a two-story-tall robotic spacecraft will begin a journey of many years to reach and explore the exciting realm of Saturn, the most distant planet that can easily be seen by the unaided human eye. In addition to Saturn's interesting atmosphere and interior, its vast system contains the most spectacular of the four planetary ring systems, numerous icy satellites with a variety of unique surface features. A huge magnetosphere teeming with particles that interact with the rings and moons, and the intriguing moon Titan, which is slightly larger than the planet Mercury, and whose hazy atmosphere is denser than that of Earth, make Saturn a fascinating planet to study. The Cassini mission is an international venture involving NASA, the European Space Agency (ESA), the Italian Space Agency (ASI), and several separate European academic and industrial partners. The mission is managed for NASA by JPL. The spacecraft will carry a sophisticated complement of scientific sensors to support 27 different investigations to probe the mysteries of the Saturn system. The large spacecraft will consist of an orbiter and ESA's Huygens Titan probe. The orbiter mass at launch will be nearly 5300 kg, over half of which is propellant for trajectory control. The mass of the Titan probe (2.7 m diameter) is roughly 350 kg. The mission is named in honor of the seventeenth-century, French-Italian astronomer Jean Dominique Cassini, who discovered the prominent gap in Saturn's main rings, as well as the icy moons Iapetus, Rhea, Dione, and Tethys. The ESA Titan probe is named in honor of the exceptional Dutch scientist Christiaan Huygens, who discovered Titan in 1655, followed in 1659 by his announcement that the strange Saturn "moons" seen by Galileo in 1610 were actually a ring system surrounding the planet. Huygens was also famous for his invention of the pendulum clock, the first accurate timekeeping device. http://photojournal.jpl.nasa.gov/catalog/PIA04603