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 January 20
       [2]A big ball that is mostly yellow is shown. The ball has many
     circular and irregular regions that are different colors, typically
     brown or olive green. Please see the explanation for more detailed
                                information.

                              Io in True Color
              Image Credit: [3]NASA, [4]JPL, [5]Galileo Project

   Explanation: The strangest moon in the [6]Solar System is bright
   yellow. The [7]featured picture, an attempt to show how Io would appear
   in the "true colors" perceptible to the average human eye, was taken in
   1999 July by the [8]Galileo spacecraft that orbited Jupiter from 1995
   to 2003. Io's colors derive from [9]sulfur and molten [10]silicate
   rock. The unusual [11]surface of Io is kept very young by its system of
   [12]active volcanoes. The intense [13]tidal gravity of [14]Jupiter
   stretches [15]Io and damps wobbles caused by Jupiter's other
   [16]Galilean moons. The resulting [17]friction greatly heats [18]Io's
   interior, causing [19]molten rock to explode through the surface.
   [20]Io's volcanoes are [21]so active that they are effectively turning
   the whole moon inside out. Some of [22]Io's volcanic lava is so hot it
   [23]glows in the dark.

                       Tomorrow's picture: open space
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    Authors & editors: [35]Robert Nemiroff ([36]MTU) & [37]Jerry Bonnell
                                 ([38]UMCP)
          NASA Official: Amber Straughn [39]Specific rights apply.
            [40]NASA Web Privacy, [41]Accessibility, [42]Notices;
                A service of: [43]ASD at [44]NASA / [45]GSFC,
                         [46]NASA Science Activation
                           & [47]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2601/iotruecolor_galileo_2796.jpg
   3. https://www.nasa.gov/
   4. https://www.jpl.nasa.gov/
   5. https://science.nasa.gov/mission/galileo/
   6. https://science.nasa.gov/solar-system/solar-system-facts/
   7. https://science.nasa.gov/photojournal/global-image-of-io-true-color/
   8. https://science.nasa.gov/mission/galileo/
   9. http://periodic.lanl.gov/16.shtml
  10. https://en.wikipedia.org/wiki/Silicate_mineral
  11. https://science.nasa.gov/jupiter/jupiter-moons/io/facts/#h-potential-for-life
  12. https://apod.nasa.gov/apod/ap960805.html
  13. https://en.wikipedia.org/wiki/Tidal_force
  14. https://science.nasa.gov/jupiter/
  15. https://youtu.be/GkfDnIQsEXs
  16. https://apod.nasa.gov/apod/ap001118.html
  17. https://en.wikipedia.org/wiki/Friction
  18. http://en.wikipedia.org/wiki/Io_(moon)
  19. https://apod.nasa.gov/apod/ap070918.html
  20. http://www.youtube.com/watch?v=GdkOngxCqQo
  21. https://youtu.be/mt084vYqbnY
  22. https://apod.nasa.gov/apod/ap070211.html
  23. https://ui.adsabs.harvard.edu/abs/1998Icar..135..181M/abstract
  24. https://apod.nasa.gov/apod/ap260119.html
  25. https://apod.nasa.gov/apod/archivepix.html
  26. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  27. https://apod.nasa.gov/apod/lib/aptree.html
  28. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  29. https://apod.nasa.gov/apod/calendar/allyears.html
  30. https://apod.com/feed.rss
  31. https://apod.nasa.gov/apod/lib/edlinks.html
  32. https://apod.nasa.gov/apod/lib/about_apod.html
  33. https://asterisk.apod.com/discuss_apod.php?date=260120
  34. https://apod.nasa.gov/apod/ap260121.html
  35. http://www.phy.mtu.edu/faculty/Nemiroff.html
  36. http://www.phy.mtu.edu/
  37. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  38. http://www.astro.umd.edu/
  39. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  40. https://www.nasa.gov/about/highlights/HP_Privacy.html
  41. https://www.nasa.gov/general/accessibility/
  42. https://www.nasa.gov/privacy/
  43. https://astrophysics.gsfc.nasa.gov/
  44. https://www.nasa.gov/
  45. https://www.nasa.gov/centers/goddard/
  46. https://science.nasa.gov/learners
  47. http://www.mtu.edu/