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Moon and Saturn

March 11, 2015

With the next “Star Wars” movie scheduled to open late this year, fans are already thinking of droids, light sabers, and death stars. We can’t help with the first two, but we can point you to a death star: Mimas, one of the moons of Saturn.

Cassini view of Mimas, with its giant crater at lower rightCassini view of Mimas, with its giant crater at lower rightMimas is about 250 miles wide, and is made of ice mixed with rock. Its most prominent feature is a 90-mile-wide impact crater. It’s so big and round that it makes Mimas look like a death star.

A recent study used pictures of its surface to probe its interior. A research team used pictures snapped by the Cassini spacecraft to produce a 3-D model of Mimas. The team then plotted the positions of surface features at different points in its orbit.

The pictures revealed that Mimas “wobbles” on its axis. From the size and shape of the wobble, the researchers created two working models of Mimas’s interior.

In one model, the moon’s core is shaped a bit like a rugby ball. And in the other, there’s an ocean of liquid water about 15 to 20 miles beneath Mimas’s crust. The moon’s orbit is slightly lopsided, so the gravitational pull of Saturn and some of the planet’s other moons pull and stretch Mimas. That may heat its interior enough to melt some of its ice, creating a big ocean inside a big “death star.”

Look for Saturn close to the lower right of our own moon at first light tomorrow. Saturn looks like a bright star. And scientists have been studying the Moon’s interior as well. More about that tomorrow.


Script by Damond Benningfield, Copyright 2015

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