“Death Star” Moon Gets Its Close-Up

“That’s no moon. Oh, wait, yes it is!”
—Image courtesy NASA/JPL/Space Science Institute

When Luke said that TIE fighter was headed toward a “small moon,” he must have had Mimas on his mind.

Since the 1980s this small Saturn moon has been likened to the fictional Death Star, thanks to its most noticeable blemish, the 88-mile-wide (140-kilometer-wide) Herschel Crater.

Of course, while the Death Star’s “crater” was really a weapon that could obliterate planets, Mimas’s crater was made by an impact that likely almost shattered the tiny moon.

For starters, the basin’s width is almost a third of the width of the moon as a whole—for a rocky body, take a hit like that without getting rattled.

In fact, fractures on the other side of Mimas appear to have been made by the impact shock as it traveled clean through the moon.
The second Death Star? Nah, just an incomplete image from Cassini.

—Image courtesy NASA/JPL/Space Science Institute

Despite this blow and some other serious, if smaller scale, cratering, Mimas is the tiniest body that stays round thanks to its own gravity.

Scientifically speaking, this is a moon we would like to know better.

Today NASA unveiled some of its most detailed pictures yet of Mimas, taken during a close approach by the Cassini orbiter.

Cassini zoomed in for the flyby last week, making its closest pass on Saturday, at a mere 5,900 miles (9,500 kilometers) from the moon’s surface.

The raw pictures took a few days to get beamed back to Earth, landing in NASA’s lap just yesterday. But the unprocessed snapshots are already revealing some of Mimas’s secrets, including the bright and amazingly steep slopes inside Herschel.
Mimas’s surface, up close and personal

—Image courtesy NASA/JPL/Space Science Institute

“This flyby has been like looking at a cell or an onion skin under the microscope for the first time,” Bonnie Buratti, one of the science team leaders, said in a statement.

“We’d seen the large crater from afar since the early 1980s, but now its small bumps and blemishes are all clearly visible.”

Later processing and study of the pictures could offer even more tidbits about the pockmarked moon, such as what its exact composition might be, why its south pole is lacking in large craters, and just how it influences Saturn’s rings.
Mimas (near) and Epimetheus (far) lie along Saturn’s ringplane in a natural-color snapshot from Cassini.

—Image courtesy NASA/JPL/Space Science Institute

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