Clair de Mercury

By Phil Plait | September 30, 2011 6:30 am

I know I just posted a MESSENGER photo of craters, but this one is different and spectacular enough that I figure, why not? I love a big, splashy, wide-angle shot of a rayed crater! So here’s the lovely, 80-km wide impact crater Debussy on the surface of Mercury:

[Click to haphaestenate.]

Craters make rays when the ejected material blasted out forms long plumes which fall across the surface. On airless worlds, those trajectories are ballistic, heading straight out from the center of the impact. Deeper material tends to be a lighter shade than surface material, so the interior of the crater and the rays are lighter than surrounding surface stuff. You can also see what’s called the apron, the layer of material that falls immediately around the crater, surrounding it (that’s more clear in an earlier image of the crater looking more straight down on it).

Rayed craters are common (even on our Moon; take a look at Tycho!), and usually indicate the impact was recent (geologically), since the rays eventually get eroded by the solar wind, cosmic rays, and subsequent meteorite impacts. Debussy is therefore one of the younger features on Mercury. It still has that youthful shine.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Related posts:

Jaw-dropping mosaic of Mercury’s battered, beautiful face
More Mercury
MESSENGER’s family portrait
Watermelon planet (a personal favorite of mine)

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (16)

  1. Messier Tidy Upper

    Looks like a giant space jellyfish made a very hard landing! 😉

  2. I notice several other younger craters in that photo (lower center, upper left, etc.). Are they secondary impacts from ejecta, or maybe smaller impactors that were accompanying the main impactor? Any thoughts on that?

  3. UmTutSut

    Any theory why the interior fill of the crater looks so much brighter than the ejecta blanket and rays?

  4. RwFlynn

    This makes me wonder if we’ll ever get to observe one of these impacts. Do we know of any that might possibly happen at some point?

  5. Messier Tidy Upper

    @ ^ RwFlynn : Well I’m not sure but its quite possible that at the end of the MESSENGER mission they’ll deliberately crash the spaceprobe into the surface to get some final close ups & go out with a BANG! 😉

    Of course, there won’t be a spacecraft orbiting the planet then to view the resultant explosion and crater. :-(

    If folks are interested, there’s a good Mercury clip here :

    which is one of my youtube faves. :-)

    Plus here :

    which is another too.

    Meanwhile in other news (going a bit off topic, sorry) there’s this re-evaluation :

    of the number of asteroids roaming the inner surface and threatening to make craters on the inner planets, incl. one’s like Debussy on Mercury. The numbers quoted seem rather implausibly precise for such estimates but its interesting news Death-from-the-skies~wise.

    BA, can I please put in a request if I may for your thoughts on that, & also your views on the Chinese space station launch & the new NASA Space Launch System?

  6. chris j.

    i can’t help noticing that the rays are not all in straight lines from the crater. i can’t tell if the rays are bisected by scarps, or if there is some other obvious geological (hermelogical?) explanation.

    oh yeah, and “haphaestenate” refers to the wrong naked greek dude. a better neologism would be hermenate, or perhaps hermesenate.

  7. Michael Swanson

    Phil, please. Post as many pictures of Mercury as you like. We don’t mind.

  8. Joseph G

    I love how features on Mercury are named after artists and philosophers. It gives the Mercurian geography (Merceography? Hermeoraphy?) such a romantic flair.
    Nothing wrong with giving scientists their due, but it’s nice that the humanities get represented, too 😛

  9. Grizzly

    “Claire de lune” is a composition by Debussy.
    “Claire de Moon” is not.
    So why “Claire de Mercury”, would it not be “Claire de Mercure”?

  10. DrFlimmer

    That must be actually the northern or southern geographical pole, where the planet is penetrated by the stick that keeps it on track while rushing through space.

  11. Ganzy

    Man, Mercury looks baked. Shallow looking craters in comparison to moon.

  12. BruceJ

    Come now, we ALL know why Tycho has rays and it’s not got anything to do with ejecta :-)

  13. Infinite123Lifer

    There is indeed a GiganEnormAsaurusRex piece of art on Mercury. It is in the form of a Sun. How peculiar. How spectacular. Its like a charcoal sketching on the grandest canvas.

  14. @ ^ Infinite123Lifer : Mercury – either planet or the element would make a pretty tough “canvas” for artists to work on! 😉

    One day in the future maybe Mercury will see human visitors and colonists make art there but it won’t be for a long while especially at the rate we’re going. (Or rather not going.)

  15. dcsohl

    Shouldn’t it be “click to enhermenate”?

  16. Matt B.

    One adjective for Hermes is “hermetic”, as in hermetically sealed, so the stem is “hermet-” and you get “hermetology” and “hermetography”. If reptiles lived there, people that study them would be hermetological herpetologists. 😀


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