An unusual view of the Death Star moon

By Phil Plait | June 21, 2012 6:45 am

If you showed me this picture with no preamble, I’d know it was from Cassini, and showed a moon of Saturn, but I’d be baffled as to which one it is:

[Click to ensithenate.]

If you told me it was Mimas, I’d be surprised… and I was when I saw it! But it’s true. Mimas is a 400 km ball of mostly ice (and some rock) orbiting Saturn about 180,000 km out. From this angle, Cassini was looking down at the north pole from a steep angle, and that’s not how we usually see it.

This is how we usually see it! The giant crater Herschel dominates the face of the moon, giving it as definite Vaderesque feel. But in the big image the crater isn’t visible, so the landscape looks markedly different.

This image was processed by Ian Regan, who notes that the blue band you can see around the edge of the moon is real. It’s a bluer region that wraps around the equatorial regions of Mimas, the origin of which is still something of a mystery. However, it does match the very odd thermal pattern seen by cameras on board Cassini, a pattern that makes Mimas look like a giant PacMan in the sky.

Cassini takes so many pictures it’s ironically not surprising that some will be surprising. Still, when it comes to astronomy, surprises are fun. They’re also a chance to learn something — as I did since I didn’t know about the blue band. And I also learned that even a familiar place can look very different if you get a different angle on it.


Related Posts:

- Wocka wocka wocka Mimas wocka wocka
- Side view of a Death Star moon
- Dione and Mimas have a mutual event
- OMG! They killed Mimas!

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: Cassini, Ian Regan, Mima, Saturn

Comments (12)

  1. John T

    That’s no moon! Oh wait, it is…

  2. From the looks of that, Alan Shephard’s moon-struck golf ball seems to have gone a ve-ery looooong way indeed. Plus picked up quite a large frosting of space ice on its journey too! ;-)

  3. That’s no moon… It’s a space sta- wait, I was wrong. It *is* a moon. Sorry. Carry on.

  4. Jimbeau

    I’m wondering if the “ripples” visible on the surface were caused by shock waves from the impact that formed the crater.

  5. That’s no moon, it’s a… oh wait. Two other dudes have made this joke already. Damn.

  6. Matt B.

    I’m also seeing a latitudinal trench in the polar view. It resembles the grooves on other moons and asteroids that make one think that boulders have rolled over them. The groove should be at about 45 degrees north. I’d need an embiggenable equatorial view of the back side to compare.

  7. Don’t be too proud of this geological terror you’ve discovered. The ability to orbit a planet is insignificant next to the power of the Force.

  8. Jon Hanford

    Matt B.:

    “I’d need an embiggenable equatorial view of the back side to compare.”

    Would this work?…… http://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Mimas_map_PIA_12780.jpg/1280px-Mimas_map_PIA_12780.jpg

    I can see several E-W grooves in the equatorial region between 240 and 330 degrees longitude on Mimas. Maybe these are related to the formation of Herschel and similar to the grooved terrain on Phobos sometimes attributed to the formation of Stickney(although a recent Mars Express study suggests otherwise): http://en.wikipedia.org/wiki/Stickney_%28crater%29

  9. ND

    I love the shadows in the craters. They give the craters some depth.

  10. Matt B.

    I love the depth of the craters. It gives the craters some shadows. ;)

  11. Thanks for a great write up Phil!

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