Cassini View of Dione

Since it entered Saturnian orbit on July 1st, 2004, the Cassini spacecraft has changed our view of Saturn and its moons.  It is a dynamic gas giant with unique and fascinating moons that have their own characteristics that make them seem more like small, rocky, planets than moons of a gas giant.  Cassini has been delivering amazing science for over a decade, and it’s next journey lies in a polar orbit of Saturn, where it will dive through Saturn’s rings, giving the most detailed and close up views of the tiny ice particles that compose them.  Before this journey, Cassini is undergoing a series of close passes of larger Saturnian moons.  Most recently it flew within 500 Km of the moon Dione.

Dione from Cassini’s recent close pass. Credit: NASA/JPL-Caltech/Space Science Institute

Dione is a fascinating moon, mainly because it is heavily cratered on just one side.  This is not usually that interesting, as rocky moons are often more heavily cratered on their leading side as they orbit.  the amazing thing about Dione is that the heavy cratering is on the wrong side.  It’s on the trailing side of its orbit.

Since Dione is small, its likely that a large impact, leaving a 35 Km wide crater, could have spun the planet around after most of the major impacts had occurred, at which point it became tidally locked with Saturn.  It’s amazing to think that such incredible impacts can happen in the solar system, releasing enough energy to significantly change the orbit and spin of a large moon.

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