CICLOPS: Cassini Imaging Central Laboratory for OPerationS
The Crater Gradient

The Crater Gradient
PIA 08956

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  Cassini investigates the craters and deep valleys on Dione during a close approach in April 2007.

Significant variations in the density of impact craters on the surface of Dione can be seen here, with more craters seen on the right side of this mosaic (on Dione's sub-Saturn hemisphere) than on the left (on Dione's anti-Saturn hemisphere). The southern end of the bright Palatine Linea fracture system can be seen near the bottom of the mosaic. Along the terminator, at lower left, part of a large impact basin can be seen.

The mosaic is an orthographic projection centered at 33 degrees South, 74 degrees West, over the southern part of Dione's leading hemisphere. An orthographic view is most like the view seen by a distant observer looking through a telescope. North on Dione (1,123 kilometers, 698 miles across) is up and rotated 6 degrees to the right.

The monochrome view uses a combination of images taken with spectral filters sensitive to wavelengths of light centered at 338, 568 and 930 nanometers.

The images in this mosaic were taken with the Cassini spacecraft narrow-angle camera on April 24, 2007 at a distance of approximately 121,000 kilometers (75,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 55 degrees. Image scale is 723 meters (2,371 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 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: June 6, 2007 (PIA 08956)
Image/Caption Information

Alliance Member Comments
Mercury_3488 (Feb 3, 2008 at 3:27 PM):
This superb image in my opinion, is very revealing.

Dione is seen here displaying a multitude of terrains.

Four main points I noticed.

1). The northern region on the terminator. To me that area looks fairly 'recently' resurfaced. General lack of craters, furrowed appearance, looks like an expansive cryovolcanic lava plain.

2). The canyons. Particularly those at the bottom right. Did the crust crack when the icy mantle beneath froze & expanded beneath an already brittle ice crust? This looks similar to what Voyager 2 imaged on the Uranian moon Ariel & I also suspect DAWN may find at dwarf planet 1 Ceres. Would be interesting to see those canyons at high resolution. Look like graben to me.

3). Tall central peaks in some of the larger craters. Rebounding crater floors, nothing unusual there per se, but on Dione seem to be very pronounced, more so than on the other moons. Also evidence of a softer mantle beneath a brittle crust.

4). Irregular crater density. Similar to point 1, but some areas seem deceptively smooth, rather than furrowed. Diapirs perhaps?

I know I have made a few posts today, but I am new & have a lot of ideas / observations I would like to share & talk about.

It is great to see that Dione has a major part to play in the extended mission. Can I request the pass to be as close as possible?

One question I do have, is there any info on the potential interior of Dione? I suspect Dione is differentiated, with a definate core, mantle & crust. Has tracking of Cassini, revealed anything of that nature during the close pass way back on Tuesday 11th October 2005?