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Saturn’s Death-Star Moon: Mimas


A view of Mimas from the Cassini spacecraft. Credit:  NASA/JPL/Space Science Institute

A view of Mimas from the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute

Saturn’s moon Mimas was discovered by William Herschel in 1789, more than 100 years after Saturn’s larger moons were uncovered. It’s the innermost of Saturn’s larger moons, and the 8th moon orbiting Saturn. You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Mimas measures 397 km across, and orbits at an altitude of 185,000 km above the center of Saturn. Mimas is just large enough that it pulls itself into a roughly spherical shape through gravity.

The density of Mimas is just a little greater than the density of water, which means that it’s mostly composed of water ice, with a small amount of rock.

The most distinct feature of Mimas is the giant crater Herschel, named after the discoverer. It measures 130 km across, and the force of the impact that created the crater much have been so hard that it almost shattered Mimas apart. The large crater gives Mimas the appearance of the Death Star from Star Wars.

It’s believed that the craters on Mimas have been around since the beginning of the Solar System. It’s so heavily cratered that new impacts will overwrite old craters. There just isn’t any part of the moon that hasn’t been pounded by impacts.

Here’s an article from Universe Today about Mimas, and here’s another.

Another great resource about Mimas is Solar Views, and you can get even more info from the Nine Planets.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.


Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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