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 July 5
    [2]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: [3]NASA, [4]ESA, [5]JPL, [6]SSI, [7]Cassini Imaging Team

   Explanation: What has happened to Saturn's moon Iapetus? Vast sections
   of [8]this strange world are dark as [9]coal, while others are as
   [10]bright as snow. To help better understand this unusually tinted
   moon, in 2007 [11]NASA directed the [12]robotic Cassini spacecraft then
   orbiting [13]Saturn to swoop within 2,000 kilometers. [14]Pictured
   here, from about 75,000 kilometers out, is the hemisphere of Iapetus
   that is [15]always trailing. A [16]large impact crater seen in the
   south spans 500 kilometers and appears superposed on an [17]older
   crater of similar size. The [18]dark material is seen increasingly
   coating the easternmost part of [19]Iapetus, darkening craters and
   highlands alike. A [20]leading hypothesis is that the dark material is
   mostly a form of carbon-rich soil leftover from when relatively warm
   but dirty ice [21]sublimates. An initial coating of this [22]dark
   material may have been [23]effectively painted on by the accretion of
   meteor-liberated debris from [24]other moons.

                Jigsaw Moon: [25]Astronomy Puzzle of the Day
                   Tomorrow's picture: dueling space bands
     __________________________________________________________________

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    Authors & editors: [37]Robert Nemiroff ([38]MTU) & [39]Jerry Bonnell
                                 ([40]UMCP)
          NASA Official: Amber Straughn [41]Specific rights apply.
            [42]NASA Web Privacy, [43]Accessibility, [44]Notices;
                A service of: [45]ASD at [46]NASA / [47]GSFC,
                         [48]NASA Science Activation
                           & [49]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2607/iapetus4_cassini_4100.jpg
   3. https://www.nasa.gov/
   4. https://www.esa.int/
   5. https://www.jpl.nasa.gov/
   6. https://www.spacescience.org/
   7. https://ciclops.org/
   8. https://science.nasa.gov/saturn/moons/iapetus/
   9. https://en.wikipedia.org/wiki/Coal
  10. https://www.earthdata.nasa.gov/topics/cryosphere/albedo
  11. https://www.nasa.gov/about/
  12. https://science.nasa.gov/mission/cassini/spacecraft/cassini-orbiter/
  13. https://apod.nasa.gov/apod/ap200419.html
  14. https://science.nasa.gov/photojournal/the-other-side-of-iapetus/
  15. https://en.wikipedia.org/wiki/Tidal_locking
  16. https://en.wikipedia.org/wiki/Engelier
  17. https://en.wikipedia.org/wiki/Gerin_(crater)
  18. https://apod.nasa.gov/apod/ap070914.html
  19. https://en.wikipedia.org/wiki/Iapetus_(moon)
  20. https://ui.adsabs.harvard.edu/abs/2005DPS....37.3908S/abstract
  21. https://en.wikipedia.org/wiki/Sublimation_(phase_transition)
  22. https://www.esa.int/Science_Exploration/Space_Science/Cassini-Huygens/Dark-stained_Iapetus
  23. https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRrzYXbehmVESHlOweeRMxQ9RZECGsss1-hWx2p70VHlg&s=10
  24. https://apod.nasa.gov/apod/ap180514.html
  25. https://www.scigames.org/apps/webjigsaw2/index.php
  26. https://apod.nasa.gov/apod/ap260704.html
  27. https://apod.nasa.gov/apod/archivepix.html
  28. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  29. https://apod.nasa.gov/apod/lib/aptree.html
  30. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  31. https://apod.nasa.gov/apod/calendar/allyears.html
  32. https://apod.com/feed.rss
  33. https://apod.nasa.gov/apod/lib/edlinks.html
  34. https://apod.nasa.gov/apod/lib/about_apod.html
  35. https://asterisk.apod.com/discuss_apod.php?date=260705
  36. https://apod.nasa.gov/apod/ap260706.html
  37. https://www.mtu.edu/physics/department/faculty/nemiroff/
  38. https://www.mtu.edu/physics/
  39. https://inspirehep.net/authors/1073087
  40. http://www.astro.umd.edu/
  41. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  42. https://www.nasa.gov/about/highlights/HP_Privacy.html
  43. https://www.nasa.gov/general/accessibility/
  44. https://www.nasa.gov/privacy/
  45. https://science.gsfc.nasa.gov/astrophysics/
  46. https://www.nasa.gov/
  47. https://www.nasa.gov/centers/goddard/
  48. https://science.nasa.gov/learn/about-science-activation/
  49. http://www.mtu.edu/