* Astronomy

Blobrana · L

RE: Iapetus

Blobrana · L

Since the discovery of Iapetus by G. D. Cassini, in 1672, it has been known that the leading hemisphere of this Saturnian satellite is one order of magnitude darker than the trailing hemisphere.
Since the Cassini spacecraft entered the Saturnian orbit, several high-quality images of the dark hemisphere of Iapetus have been obtained, in particular during the Dec 31 2004 flyby of this satellite.
These images revealed the presence of a large equatorial ridge in the dark hemisphere of Iapetus.

Planetary geologists have assumed this seam is volcanic in origin.
Paulo C.C. Freire of the Arecibo Observatory has propose that this ridge and the dark coating of the hemisphere on which it lies are intimately interlinked and are the result of a collision with the edge of a primordial Saturnian ring, ultimately caused by a sudden change in the orbit of Iapetus.
The model naturally explains all of the unique features of this satellite; like that equatorial ridge…

The new study discuses some of the possibilities for Iapetus orbit change
and its collision with Saturns rings…

Read more (PDF)

-- Edited by Blobrana at 21:38, 2005-05-12

Blobrana · L

This image was taken with the Cassini spacecraft narrow-angle camera on March 19, 2005, through spectral filters sensitive to wavelengths of infrared light cantered at 752 nanometres. The view was acquired at a distance of approximately 1.4 million kilometres from Iapetus.

The view shows one of the huge impact basins on the terminator of Saturn's moon Iapetus and a smaller, but still fairly large, crater near the southern bright-dark boundary. Just visible near the western limb, in the dark territory of Cassini Regio, is the moon's mysterious equatorial ridge. The ridge was discovered in Cassini images and reaches 20 kilometres high in places.
This view shows principally the leading hemisphere on Iapetus. North is up and tilted 15 degrees to the right. Iapetus is 1,468 kilometres across.