                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                 2021 May 31

                     Mimas: Small Moon with a Big Crater
    Image Credit & Copyright: NASA, JPL-Caltech, Space Science Institute,
                                   Cassini

   Explanation: Whatever hit Mimas nearly destroyed it. What remains is
   one of the largest impact craters on one of Saturn's smallest round
   moons. Analysis indicates that a slightly larger impact would have
   destroyed Mimas entirely. The huge crater, named Herschel after the
   1789 discoverer of Mimas, Sir William Herschel, spans about 130
   kilometers and is featured here. Mimas' low mass produces a surface
   gravity just strong enough to create a spherical body but weak enough
   to allow such relatively large surface features. Mimas is made of
   mostly water ice with a smattering of rock - so it is accurately
   described as a big dirty snowball. The featured image was taken during
   the closest-ever flyby of the robot spacecraft Cassini past Mimas in
   2010 while in orbit around Saturn.

                    Interactive: Take a trek across Mimas
                    Tomorrow's picture: streaks of Orion
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

