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.

                                2021 July 13

           IFRAME: [2]https://solarsystem.nasa.gov/gltf_embed/2381

                    Saturn's Iapetus: Painted Moon in 3D
   Image Credit: [3]NASA, [4]ESA, [5]JPL, [6]SSI, [7]Cassini Imaging Team;
                          3D Rendering: NASA's VTAD

   Explanation: What has happened to Saturn's moon Iapetus? Vast sections
   of [8]this strange world are dark brown, while others are as bright
   white. The composition of the dark material is unknown, but [9]infrared
   [10]spectra indicate that it possibly contains some dark form of
   [11]carbon. [12]Iapetus also has an unusual [13]equatorial ridge that
   makes it appear like a [14]walnut. To help better understand this
   seemingly painted moon, [15]NASA directed the [16]robotic Cassini
   spacecraft orbiting Saturn to swoop [17]within 2,000 kilometers in
   2007. Iapetus is [18]pictured here in 3D. A huge impact crater seen in
   the south spans a tremendous 450 kilometers and appears superposed on
   an [19]older crater of similar size. The [20]dark material is seen
   increasingly coating the easternmost part of [21]Iapetus, darkening
   craters and highlands alike. [22]Close inspection indicates that the
   dark coating typically faces the moon's equator and is less than a
   meter thick. A [23]leading hypothesis is that the dark material is
   mostly dirt leftover when relatively warm but dirty ice [24]sublimates.
   An initial coating of [25]dark material may have been effectively
   painted on by the accretion of meteor-liberated debris from [26]other
   moons.

                     Tomorrow's picture: black hole eats
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    Authors & editors: [38]Robert Nemiroff ([39]MTU) & [40]Jerry Bonnell
                                 ([41]UMCP)
          NASA Official: Phillip Newman [42]Specific rights apply.
              [43]NASA Web Privacy Policy and Important Notices
                A service of: [44]ASD at [45]NASA / [46]GSFC
                           & [47]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://solarsystem.nasa.gov/gltf_embed/2381
   3. https://www.nasa.gov/
   4. https://www.esa.int/
   5. https://www.jpl.nasa.gov/
   6. http://www.spacescience.org/
   7. http://ciclops.org/
   8. https://en.wikipedia.org/wiki/Iapetus_(moon)
   9. https://science.nasa.gov/ems/07_infraredwaves
  10. https://science.nasa.gov/ems/01_intro
  11. https://periodic.lanl.gov/6.shtml
  12. https://trek.nasa.gov/iapetus/
  13. https://apod.nasa.gov/apod/ap050201.html
  14. http://www.whfoods.com/genpage.php?tname=foodspice&dbid=99
  15. https://www.nasa.gov/about/index.html
  16. https://en.wikipedia.org/wiki/Cassini_spacecraft
  17. https://apod.nasa.gov/apod/ap070919.html
  18. https://solarsystem.nasa.gov/resources/2381/iapetus-3d-model/
  19. https://apod.nasa.gov/apod/ap060530.html
  20. https://apod.nasa.gov/apod/ap070914.html
  21. https://apod.nasa.gov/apod/ap060103.html
  22. http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/
  23. https://ui.adsabs.harvard.edu/abs/2005DPS....37.3908S/abstract
  24. http://en.wikipedia.org/wiki/Sublimation_(chemistry)
  25. http://www.youtube.com/watch?v=DYvITG_TDfE
  26. https://apod.nasa.gov/apod/ap180514.html
  27. https://apod.nasa.gov/apod/ap210712.html
  28. https://apod.nasa.gov/apod/archivepix.html
  29. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  30. https://apod.nasa.gov/apod/lib/aptree.html
  31. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  32. https://apod.nasa.gov/apod/calendar/allyears.html
  33. https://apod.nasa.gov/apod.rss
  34. https://apod.nasa.gov/apod/lib/edlinks.html
  35. https://apod.nasa.gov/apod/lib/about_apod.html
  36. http://asterisk.apod.com/discuss_apod.php?date=210713
  37. https://apod.nasa.gov/apod/ap210714.html
  38. http://www.phy.mtu.edu/faculty/Nemiroff.html
  39. http://www.phy.mtu.edu/
  40. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  41. http://www.astro.umd.edu/
  42. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  43. https://www.nasa.gov/about/highlights/HP_Privacy.html
  44. https://astrophysics.gsfc.nasa.gov/
  45. https://www.nasa.gov/
  46. https://www.nasa.gov/centers/goddard/
  47. http://www.mtu.edu/