Astronomy Picture of the Day

   [1]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
    [2]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: [3]JAXA, [4]ISAS

   Explanation: Why are parts of this asteroid's surface so smooth? The
   answer seems likely to do with the dynamics of an [5]asteroid that is a
   loose [6]pile of rubble rather than a solid rock. The [7]unusual
   asteroid [8]Itokawa was visited by the [9]Japanese spacecraft
   [10]Hayabusa in 2005 which imaged and documented its unusual structure
   and mysterious [11]lack of craters. [12]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 [13]Brazil nut effect. The robotic Hayabusa
   actually [14]touched down on one of the smooth patches, dubbed the
   [15]MUSES Sea, and collected [16]soil samples. These samples were
   [17]returned to Earth and are not only giving clues to the ancient
   history of [18]this unusual asteroid, but also about the early years of
   our entire [19]Solar System. Computer simulations show that 500-meter
   [20]asteroid Itokawa may [21]impact the Earth within the next few
   million years.

                  Rocking Space: Today is [22]Asteroid Day
                       Tomorrow's picture: open space
     __________________________________________________________________

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    Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell
                                 ([37]UMCP)
          NASA Official: Amber Straughn [38]Specific rights apply.
            [39]NASA Web Privacy, [40]Accessibility, [41]Notices;
                A service of: [42]ASD at [43]NASA / [44]GSFC,
                         [45]NASA Science Activation
                           & [46]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2606/itokawa07_hayabusa_1080.jpg
   3. https://www.jaxa.jp/
   4. https://www.isas.jaxa.jp/en/
   5. https://science.nasa.gov/solar-system/asteroids/
   6. https://daviddarling.info/encyclopedia/R/rubble-pile_asteroid.html
   7. https://apod.nasa.gov/apod/ap051116.html
   8. https://science.nasa.gov/solar-system/asteroids/25143-itokawa/
   9. https://user.iiasa.ac.at/~marek/fbook/01/geos/ja.html
  10. https://science.nasa.gov/mission/hayabusa/
  11. https://apod.nasa.gov/apod/ap051121.html
  12. https://www.science.org/doi/10.1126/science.1134390
  13. https://en.wikipedia.org/wiki/Granular_convection
  14. https://apod.nasa.gov/apod/ap190312.html
  15. https://global.jaxa.jp/article/special/hayabusa_sp3/p2_e.html
  16. https://www.planetary.org/articles/3191
  17. https://global.jaxa.jp/article/special/hayabusa/index_e.html
  18. https://apod.nasa.gov/apod/ap100619.html
  19. https://eyes.nasa.gov/apps/solar-system/#/home
  20. https://www.esa.int/ESA_Multimedia/Videos/2017/04/Visualisation_of_asteroid_Itokawa/(lang)
  21. https://i.ytimg.com/vi/1Kl4rNUTWCA/hqdefault.jpg
  22. https://asteroidday.org/
  23. https://apod.nasa.gov/apod/ap260629.html
  24. https://apod.nasa.gov/apod/archivepix.html
  25. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  26. https://apod.nasa.gov/apod/lib/aptree.html
  27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  28. https://apod.nasa.gov/apod/calendar/allyears.html
  29. https://apod.com/feed.rss
  30. https://apod.nasa.gov/apod/lib/edlinks.html
  31. https://apod.nasa.gov/apod/lib/about_apod.html
  32. https://asterisk.apod.com/discuss_apod.php?date=260630
  33. https://apod.nasa.gov/apod/ap260701.html
  34. https://www.mtu.edu/physics/department/faculty/nemiroff/
  35. https://www.mtu.edu/physics/
  36. https://inspirehep.net/authors/1073087
  37. http://www.astro.umd.edu/
  38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  39. https://www.nasa.gov/about/highlights/HP_Privacy.html
  40. https://www.nasa.gov/general/accessibility/
  41. https://www.nasa.gov/privacy/
  42. https://science.gsfc.nasa.gov/astrophysics/
  43. https://www.nasa.gov/
  44. https://www.nasa.gov/centers/goddard/
  45. https://science.nasa.gov/learn/about-science-activation/
  46. http://www.mtu.edu/