CICLOPS: Cassini Imaging Central Laboratory for OPerationS
The Other Side of Iapetus

The Other Side of Iapetus
PIA 08384

Avg Rating: 8.60/10

Full Size 4100x4100:
PNG 15.3 MB
TIFF 28.3 MB

Half Size 2050x2050:
PNG 4.6 MB

Quarter Size 1025x1025:
PNG 1.2 MB
  Cassini captures the first high-resolution glimpse of the bright trailing hemisphere of Iapetus. This false-color mosaic shows the entire hemisphere of Iapetus (1,471 kilometers, 914 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 Voyager 2 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 the 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 Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission, visit and the Cassini imaging team home page,

Credit: NASA/JPL/Space Science Institute
Released: October 8, 2007 (PIA 08384)
Image/Caption Information

Alliance Member Comments
djbarney (Oct 13, 2007 at 8:09 AM):
Difficult to look at because of the dark/light materials on the surface. I keep thinking they're shadows until I check the light direction !
Rich777 (Oct 11, 2007 at 4:31 PM):
Must have other snapshots of all moons in our solar system like this one.... ^^

Can you believe how many moons humans have to explore?! Just wait until we get up there and running all around in our solar zippers, flying from one end of the system to the next. Next 100 years look out. Humans have escaped!
DEChengst (Oct 10, 2007 at 12:04 PM):
Yet another work of art by the CICLOPS team :) I bet that even the best painter ever, couldn't have come up with an image like this.
Breitstar (Oct 9, 2007 at 8:51 PM):
How incredibly beautiful! Now I will have to change my ski trip to Enceladus to include a stop at the Space Port Resort on Iapetus. (Off season rates apply)
Red_dragon (Oct 9, 2007 at 1:08 AM):
Whew! That's NO space station...