Mystery of Saturn's Two-Faced Moon Solved Options

[TheChemist]

Carolyn Porco comments included in this space.com article :

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

[ngunn]

Why is everyone so sure about this global dusting from another moon? If the vast majority of the Cassini Regio dark material was already in the dirty ice of Iapetus and you only need a small amount of seeding material then the problem largely goes away. The albedo and spectrum of Cassini Regio should not be expected to match the seeding material, which may be pretty hard to track down at all if most of the seeding happened a long time ago. The source could have been a population of small, exhuasted (de-iced) periodic comet nuclei with aphelia close to the orbit of Saturn. These would have long since disappeared, so the search for a source may well be futile. I think it might be more fruitful to search for a 'colour' match amongst materials that might plausibly be trapped within the ice of Iapetus, or the radiation-altered products of such.