[X] My Assistant

[TheChemist]

Carolyn Porco comments included in this space.com article :

http://www.space.com/scienceastronomy/0710...ni-iapetus.html

[alan]

Its the leading hemisphere because the dust is moving in a nearly circular orbit in the opposite direction as Iapetus.



Here's some fodder for the light on dark/dark on light debate. This is a piece of CICLOPS version of the Iapetus that I contrast stretched to bring out some subtle details at high latitudes.



Iapetus doesn't just have light and dark, the bright terrain near the equator are dirty in contrast to the blue-white terrain near the poles. At high latitudes you can see areas of beige on the equator facing slopes. So near the poles is it beige on white or white on beige? What was the original color of Iapetus?


I remember a paper I read before the New Year's Iapetus encounter that speculated that the dark material started hitting on Iapetus before its rotation was synchronized with its orbit. This could have made the trailing side dirty without starting the runaway process because the rotation was still to fast for the daylight temperatures to reach a critical temperature. This may have provided the seed needed to start the darking process inside the craters on the trailing side.