The moon that almost wasn't

By Phil Plait | November 8, 2010 2:08 pm

Cassini images of Saturn and its environs never get tiresome. And in fact, they can be downright jolting… like this stunning shot of the icy moon Mimas.

cassini_crescent_mimas

Cassini was 100,000 km (60,000 miles) from the small moon when it captured this moody image. It shows a view we can never get from Earth: a crescent Mimas, with the Sun well off to the side.

The giant crater is called Herschel, and it’s a whopping 130 km (80 miles) across. Whatever hit Mimas eons past was huge, and had it been any bigger, or moving any faster, the moon itself may have shattered. In fact, there’s some thinking that this happens to some smaller bodies in the solar system; they can get hit so hard they do shatter, and if the event isn’t too energetic the pieces can recoalesce, reintegrate. This may be why some asteroids are so low in density; they’re essentially rubble piles, like bags of glass.

Mimas was spared that fate those many, many years ago. What was left was an icy moon with a single brooding eye… reminding us that when we stare into the abyss, sometimes the abyss stares back.


Image credit: NASA/JPL/Space Science Institute

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Cassini, Herschel, Mimas, Saturn

Comments (50)

  1. chris

    That’s no moon!

  2. Mimas has always reminded me of the Death Star. Wonder if this was inspiration for Lucas?

  3. Owen

    Reminds me of “The Death Star”

  4. Suicidal Zebra

    In a strange twist of fate, close-up images of Mimas apparently weren’t taken until 3 years after the first Star Wars film: http://www.newscientist.com/article/dn6999

  5. Jim

    #2 — Alas, no, the first close-up photos of Mimas didn’t come out until the early 80s, well after the original Star Wars was released.

  6. Gus Snarp

    When you get an image where the big crater is facing you more or less directly, like in Suicidal Zebra’s link, it doesn’t so much look like a Death Star anymore as, well something appropriate for Phil’s Wootstock talk. Just saying.

  7. Mistletoe

    “That’s no moon! It’s a… oh. It IS a moon.”

  8. Dean

    That’s no moon!

    Oh wait…it is.

    Never mind.

  9. TS

    #2 — Alas, no, the first close-up photos of Mimas didn’t come out until the early 80s, well after the original Star Wars was released.

    How do you know that George Lucas didn’t revise his films after those photos were taken?

    ;-)

  10. Mister Earl

    And now we will discuss the location of the secret rebel base.

  11. John F

    “How do you know that George Lucas didn’t revise his films after those photos were taken?”

    You want to make those of us who saw that first film during its initial theatrical run feel old don’t you?

    What I remember about Mimas was the fact that when the first photos were released EVERY journalist made a death star joke

  12. Durand

    Liking the last phrase in the article!

  13. “No one would have believe at the beginning of the twenty first century that planet Earth was being watched by beings more intelligent than humankind.”

  14. That’s no m… oh, dammit!

  15. Josh M

    Y’all see an eye or a Death Star, I see a giant cocktail olive.

  16. “That’s no space station, it’s a MOON.”

    There. That’ll be the definitive quote. :)

    I’m always impressed by the amount and depth of the craters on Mimas. The surface must have some sort of softness or resiliency to it, to have such deep craters without much outspray of ejecta or discernible boulders. They’re just kind of scooped out of the surface. I would think this is due to a not-so-dense composition? Maybe Mimas is made of creamy nougat.

  17. Archangel
  18. Zetetic

    I’ve always liked that crater in Mimas.

    What’s scary that crater is still smaller than the crater left in Chicxulub (~180km) that is thought to have killed off the dinosaurs. I wonder if the Chicxulub object would have been enough to shatter Mimas?

  19. Smitty

    The Death Star resemblance is obvious… dare I say cliched?

    But that last sentence is very Firefly.

    @ J Major & Archangel:

    Mmmmm indeed. Creamy nougaty goodness.

  20. QuietDesperation

    In the interests of being slightly different.

  21. QuietDesperation

    “But that last sentence is very Firefly.”

    Or, you know, Nietzsche.

  22. AJ in CA

    @#16 J Major: As we know, our own moon is made of green cheese, so I’m thinking Mimas is probably Brie or Camembert. Perhaps further spectrographic analysis will tell us if Mimas should be paired with Merlot or Chenin Blanc :D

    Srsly though, I think you’re right – between the low density (lots of ice), its position fairly deep in the gravity well of Saturn (as mentioned in that link), and its small size (less gravity to collapse the crater walls, not to mention they look bigger by comparison), Mimas is pretty much the perfect crater collector :)

  23. AJ in CA

    @20 Quiet Desperation:

    Theeeeere we go :)
    BTW, how do you post images? I didn’t know that was possible here.

  24. IBY

    Didn’t Uranus’ moon Miranda shatter and regroup itself?

  25. HM

    “Whoever fights monsters should see to it that in the process he does not become a monster. And when you look long into an abyss, the abyss also looks into you.” -Nietzsche

  26. TS (9):

    How do you know that George Lucas didn’t revise his films after those photos were taken?

    ;-)

    I know you put a smiley in there, but I saw the first three (episodes 4-6) in theaters during their original releases.

  27. What they don’t tell you is that Saturn’s rings used to be called “Endor”

  28. Aaron

    Are you thinking of “Alderaan”?

  29. That’s no Moon!!!

    http://www.cheappostforum. please come and post about science and discuss thing,
    i am trying to get more people to post. its not a competing forum for bautforum

  30. Messier Tidy Upper

    <3 Cassini <3 :-)

    Fantastic image of the Death Star moon Mimas. :-)

    @24.IBY : Yep. That's certainly the theory I've heard for explaining Miranda's strange nature. :-)

  31. Kullat Nunu

    According to a new theory, Mimas, other icy moons, and the rings of Saturn are leftovers of a Titan-sized moon that spiraled in and got destroyed. That would make Mimas a second-generation satellite.

  32. John Paradox

    23. AJ in CA Says:
    BTW, how do you post images? I didn’t know that was possible here.

    It’s actually the simplest I’ve found on blog software: you use HTML. For images you put the location inside (with the greater than/less than for standard HTML replaced with brackets)
    {IMG SRC=”(insert URL here)”}
    It works just like the {I}{/I} tag I used above to italicize your comment.
    CSS also works, but HTML, IMHO, is easier.

    J/P=?

  33. Messier Tidy Upper

    @22. AJ in CA Says:

    @#16 J Major: As we know, our own moon is made of green cheese, so I’m thinking Mimas is probably Brie or Camembert.

    Hang on, with all those holes that has to be *Swiss cheese* doesn’t it? ;-)

    @30. Kullat Nunu Says:

    According to a new theory, Mimas, other icy moons, and the rings of Saturn are leftovers of a Titan-sized moon that spiraled in and got destroyed. That would make Mimas a second-generation satellite.

    Cool! That’s a new idea I hadn’t heard about before. Thanks. :-)

    Whose theory is that & do you have a source or article link for more info on that, please?

  34. Messier Tidy Upper

    Off topic, sorry, but check out this comparison of the five comet’s spaceprobes have visited close up so far :

    http://epoxi.umd.edu/3gallery/20101104_Sunshine2.shtml

    via the EPOXI site here :

    http://epoxi.umd.edu/

    which has lots more Hartley 2 / EPOXI/ Deep Impact images, news and features.

    Including this :

    http://epoxi.umd.edu/3gallery/20101104_Sunshine4.shtml

    enhanced image of the comet’s jets. :-)

    (Is this time to suggest the jets be named Harrier-jump, Mirage & Stealth-fighter? ;-) )

  35. @ 24 IBY: Please don’t drag Uranus (and its twin moons) into this discussion. It’s supposed to be a family site.

  36. Shoeshine Boy

    @ 9 TS Wins. Thread over. :)

  37. Dan I.

    I hope that if hostile aliens every enter our Solar System they’ll have gotten broadcasts of Star Wars, see Mimas, and go “RETREAT! They actually have one!!!”

  38. DrFlimmer

    To follow up on #38 Dan I., we maybe should go there, dig some holes into Mimas, install some powerful lasers and, thus, build our own death star to have a defence mechanism against the aliens. Then we would actually have one, and the aliens would not even have to have seen Star Wars. And we could aim it at some bad asteroids soon enough to destroy them before they come too close to earth to be harmful (after their destruction by nukes). I guess, this is win-win situation. Let’s do it! :D

  39. Messier Tidy Upper

    @ 35. Lugodsi : Twin moons? Actually Ouranos has lots of moons!

    Twenty-seven in all are known so far :

    … divided into three groups: thirteen inner moons, five major moons, and nine irregular moons. The inner moons are small dark bodies that share common properties and origins with the planet’s rings. The five major moons are massive enough to have achieved hydrostatic equilibrium, and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces.[3] The largest of these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, and about 20 times less massive than Earth’s Moon.

    source : http://en.wikipedia.org/wiki/Uranus%27_natural_satellites

    Of course, I’d hate to be one of the first astronauts to live there .. or at least telling people I was living there anyhow. ;-)

    @38. Dan I. : LOL. :-D

  40. Nigel Depledge

    MTU (33) said:

    Hang on, with all those holes that has to be *Swiss cheese* doesn’t it?

    Not necessarily. It could be Jarlsberg.

  41. Keith Bowden

    31. Kullat Nunu Says:
    November 9th, 2010 at 12:03 am
    According to a new theory, Mimas, other icy moons, and the rings of Saturn are leftovers of a Titan-sized moon that spiraled in and got destroyed. That would make Mimas a second-generation satellite.

    “C’mon down to Bob’s Used Moon Lot! Low density! Only orbited a little ol’ planet on Sundays!”

  42. Gary Ansorge

    Right in the middle of that crater is where I plan on placing my fusion thruster. Then it will be ” To the stars Alice,,,”,,,and our space colony will be on its way.

    Gary 7

  43. AJ in CA

    This thread makes me lawl :D

  44. JupiterIsBig

    #38 Dan I. you cracked me up too !

  45. Chris Winter

    “Mimas was spared that fate those many, many years ago. What was left was an icy moon with a single brooding eye… reminding us that when we stare into the abyss, sometimes the abyss stares back.”

    Do we know how long ago that was? I ask because I’m contemplating some wild speculation: What if, eons ago, Mimas was covered with a lot more ice that was loosely consolidated or “slushy”? If the impact occurred then, it might not have been so damaging because the ice acted as a cushion of sorts. Of course, it’s more likely that the ice was hard-frozen. But if it was significantly thicker, the impact might not have come so close to shattering then-larger Mimas.

    In any case, the floor of Herschel does seem unusually shallow and level for such a large impact. Could the features have gradually sublimed away, as much of the ice is thought to have done?

  46. Elias

    While we’re all on about the pareidolia in the photo, I was thinking of using it as the desktop image on my work computer, but then the crater started looking like an areole…

  47. Brian Too

    @39. DrFlimmer,

    That’s too expensive. Dan I.’s idea is much more cost-effective. In fact the only improvement (ahem) I can make to it, is to suggest that we land a transmitter on Mimas. It’s only job is to broadcast Star Wars endlessly, thus advertising the power of those Earthlings! Oh, and we need to insert various off-hand narrative references to the “historical documents”.

  48. Hellchylde

    For those discussing the Death star look…. the first pics didn’t come out till the SECOND MOVIE was out

    “Scientists first noticed Mimas’s resemblance to the Death Star when the twin Voyager spacecraft flew past Saturn in 1980 and 1981. The second film in the movie series – The Empire Strikes Back – had just hit movie theatres, recalls Cassini deputy project scientist Linda Spilker.”

    http://www.newscientist.com/article/dn6999

    a link one already put in the comment thread .. but it bears repeating

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