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Fraser
2007-Oct-09, 03:56 PM
Saturn's moon Iapetus is one of the most mysterious objects in the Solar System. It's shaped like a football, has a strange ridge that runs along most of its equator, and it's got vastly different hemispheres. ...

Read the full blog entry (http://www.universetoday.com/2007/10/09/a-possible-explanation-for-two-toned-iapetus/)

Jerry
2007-Oct-10, 01:27 PM
If you look in the transition regions, the dark patches start at the bottoms of the craters on the solar-facing sides of the craters. Like a plowed field covered with snow, the burn of rate is a function of solar angles and reflections, and the patterns clearly reveal a dark substrate. Anyone living in a snowy climate can see this immediately. Although dust likely hastened the process on the leading side, the transition between the dark and the light side, progressing most rapidly along the equator, indicates this is a white-on-black, not a black-on-white surface. Check it out!

Dark material did not 'somehow slide down the sides of craters' and settle in the bottoms. That explanation has a lot more to do with prior expectations than careful scrutiny of Cassini's Iapetus observations.

ray
2007-Oct-11, 01:56 AM
It seems clear that the light color (snow/ice) is covering a surface that is dark. Probably the whole (Planet).

"So where does the dark material come from? Astronomers think that it didn't originate on Iapetus, but instead came from the surrounding outer moons. As Iapetus goes around its orbit, this darker material piles up on the leading hemisphere."

I don't think so.

It's not shaped like a football either.