                        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 June 30
      Dark space surrounds a gray peanut sized object. The object has a
     surface that has many rough nodules but also some relatively smooth
     sections. Please see the explanation for more detailed information.

                Unusually Smooth Sections of Asteroid Itokawa
                          Image Credit: JAXA, ISAS

   Explanation: Why are parts of this asteroid's surface so smooth? The
   answer seems likely to do with the dynamics of an asteroid that is a
   loose pile of rubble rather than a solid rock. The unusual asteroid
   Itokawa was visited by the Japanese spacecraft Hayabusa in 2005 which
   imaged and documented its unusual structure and mysterious lack of
   craters. Analyses of the border regions between smooth and rugged
   sections indicate that jostling of the asteroid might be creating
   segregation between large and small rocks near the surface, like the
   Brazil nut effect. The robotic Hayabusa actually touched down on one of
   the smooth patches, dubbed the MUSES Sea, and collected soil samples.
   These samples were returned to Earth and are not only giving clues to
   the ancient history of this unusual asteroid, but also about the early
   years of our entire Solar System. Computer simulations show that
   500-meter asteroid Itokawa may impact the Earth within the next few
   million years.

                    Rocking Space: Today is Asteroid Day
                       Tomorrow's picture: open space
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
                  NASA Web Privacy, Accessibility, Notices;
                      A service of: ASD at NASA / GSFC,
                           NASA Science Activation
                             & Michigan Tech. U.

