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The Strangest Moon In the Solar System
StartsWithABang writes Moons in our Solar System — at least the ones that formed along with the planets — all revolve counterclockwise around their planetary parents, with roughly uniform surfaces orbiting in the same plane as their other moons and rings. Yet one of Saturn's moon's, Iapetus, is unique, with a giant equatorial ridge, an orbital plane that doesn't line up, and one half that's five times brighter than the other. While the first two are still mysteries, the last one has finally been solved.
The fun is that in 2001, the bright side of Iapetus was sculpted, with the monolith in the middle. In reality the dark side is sculpted from passage through the dust ring.
The living have better things to do than to continue hating the dead.
POssibly the moon is formed from 2 bodies colliding and before it could completely settle down into a round shape it froze with that ridge remaining?
There is also the bizzare coincidence that the size of our moon, viewed from the earth is almost exactlty the same as the sun, viewed from the earth -- hence total eclipses of the sun.
Watch this Heartland Institute video
According to the IAU definition, the north pole for a major planet (or one of its satellites) is the pole on the same side of the ecliptic as the Earth's north pole, the North Celestial Hemisphere. By this definition, Venus and Uranus are retrograde rotators -- they rotate clockwise about their north poles.
For comets and minor planets (including Dwarf planets), the north pole is the pole about which the body rotates counterclockwise. So the north pole of a retrograde-rotating asteroid points into the South Celestial Hemisphere.
This brings us (as do all topics that mention the IAU) to Pluto. Pluto rotates retrograde. It was once considered a major planet, so it's north pole would have been on the same side of the ecliptic as ours. But as a dwarf planet, the opposite definition applies. Even before the 2006 decision, the convention was inconsistently applied. Papers have been published using each definition of the north pole, and they're not always good about stating which convention they used. With New Horizons on the doorstep, we're going to need consistency for mapping and navigation. So I believe the mission has decided to use the current IAU definition consistently to avoid any confusion. There was a huge fight over the coordinate system of Vesta on the Dawn mission, and we don't want that.