                        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.

                                 2026 July 5
   An unusually colored ball is shown against a dark background. The ball
    has numerous craters but a very large cratered near the lower center.
    Much of the ball is light colored, but around the right and top it is
    green-brown, with a border area that seems splattered. Please see the
                 explanation for more detailed information.

                       Saturn's Iapetus: Painted Moon
           Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

   Explanation: What has happened to Saturn's moon Iapetus? Vast sections
   of this strange world are dark as coal, while others are as bright as
   snow. To help better understand this unusually tinted moon, in 2007
   NASA directed the robotic Cassini spacecraft then orbiting Saturn to
   swoop within 2,000 kilometers. Pictured here, from about 75,000
   kilometers out, is the hemisphere of Iapetus that is always trailing. A
   large impact crater seen in the south spans 500 kilometers and appears
   superposed on an older crater of similar size. The dark material is
   seen increasingly coating the easternmost part of Iapetus, darkening
   craters and highlands alike. A leading hypothesis is that the dark
   material is mostly a form of carbon-rich soil leftover from when
   relatively warm but dirty ice sublimates. An initial coating of this
   dark material may have been effectively painted on by the accretion of
   meteor-liberated debris from other moons.

                  Jigsaw Moon: Astronomy Puzzle of the Day
                   Tomorrow's picture: dueling space bands
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

