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 right: 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
+ Full image and captionImage: Voyager MountainsImage: Inky Stains on Frozen Moon
"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 left: 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
+ Full image and caption
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
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.
RELATED MULTIMEDIA: Video file with animation, images and sound bites will
air tomorrow on NASA TV.
Media contact: Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
Preston Dyches 720-974-5859
Space Science Institute, Boulder, Colo.