[X] My Assistant

[TheChemist]

Carolyn Porco comments included in this space.com article :

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

[Greg Hullender]

Thinking about this some more, this comment

"Dusty material spiraling in from outer moons hits Iapetus head-on and causes the forward-facing side of Iapetus to look different than the rest of the moon," said Tilmann Denk, Cassini imaging scientist at the Free University in Germany.

From the original article

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

strikes me as really odd. First, a spiral isn't a possible orbit. Second, material in elliptical orbits with periapsis near Iapetus' orbit should be moving faster than it so they should impact the trailing edge, not the leading one. I'd expect material impacting the leading edge to have been in orbits with apapsis near Iapetus.

At the expense of appearing to agree with Tasp on something :-) perhaps Titan is a reasonable source for this material. Perhaps we should be looking for signs of tar stuck to Cassini's camera. :-)

--Greg