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.

                                2025 June 29
   [2]Viewed from above, a landscape on Mars features many ridges of pink
   sand. Superposed on some of these ridges are thin brown stipes. Please
             see the explanation for more detailed information.

                         Dark Sand Cascades on Mars
       Image Credit: [3]NASA, [4]HiRISE, [5]MRO, [6]LPL (U. Arizona),

   Explanation: Are these trees growing on Mars? No. Groups of dark brown
   streaks have been photographed by the [7]Mars Reconnaissance Orbiter on
   melting pinkish sand dunes covered with light frost. The [8]featured
   image was taken in 2008 April near the [9]North Pole of Mars. At that
   time, [10]dark sand on the interior of Martian sand [11]dunes became
   more and more visible as the spring Sun melted the lighter [12]carbon
   dioxide ice. When occurring near the top of a dune, [13]dark sand may
   cascade down the dune leaving [14]dark surface streaks -- streaks that
   might appear at first to be [15]trees standing in front of the lighter
   regions but cast no shadows. Objects about 25 centimeters across are
   resolved on [16]this image spanning about one kilometer. Close ups of
   some parts of this image show [17]billowing plumes indicating that the
   [18]sand slides were occurring even while the image was being taken.

   Celestial Surprise: [19]What picture did APOD feature on your birthday?
                                 (post 1995)
                      Tomorrow's picture: raining stars
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    Authors & editors: [31]Robert Nemiroff ([32]MTU) & [33]Jerry Bonnell
                                 ([34]UMCP)
          NASA Official: Amber Straughn [35]Specific rights apply.
            [36]NASA Web Privacy, [37]Accessibility, [38]Notices;
                A service of: [39]ASD at [40]NASA / [41]GSFC,
                         [42]NASA Science Activation
                           & [43]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2506/almosttrees_mro_2560.jpg
   3. http://www.nasa.gov/
   4. http://hirise.lpl.arizona.edu/
   5. https://science.nasa.gov/mission/mars-reconnaissance-orbiter/
   6. http://www.lpl.arizona.edu/
   7. http://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter
   8. http://hirise.lpl.arizona.edu/PSP_007962_2635
   9. https://apod.nasa.gov/apod/ap021224.html
  10. https://apod.nasa.gov/apod/ap060823.html
  11. http://en.wikipedia.org/wiki/Sand_dune
  12. http://www.youtube.com/watch?v=76CNkxizQuc
  13. https://apod.nasa.gov/apod/ap070805.html
  14. https://www.jpl.nasa.gov/news/recurring-martian-streaks-flowing-sand-not-water/
  15. http://en.wikipedia.org/wiki/Methuselah_(tree)
  16. http://hirise.lpl.arizona.edu/PSP_007962_2635
  17. https://apod.nasa.gov/apod/ap080311.html
  18. https://www.nasa.gov/image-article/martian-sand-dunes-spring/
  19. https://apod.nasa.gov/apod/calendar/allyears.html
  20. https://apod.nasa.gov/apod/ap250628.html
  21. https://apod.nasa.gov/apod/archivepix.html
  22. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  23. https://apod.nasa.gov/apod/lib/aptree.html
  24. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  25. https://apod.nasa.gov/apod/calendar/allyears.html
  26. https://apod.com/feed.rss
  27. https://apod.nasa.gov/apod/lib/edlinks.html
  28. https://apod.nasa.gov/apod/lib/about_apod.html
  29. https://asterisk.apod.com/discuss_apod.php?date=250629
  30. https://apod.nasa.gov/apod/ap250630.html
  31. http://www.phy.mtu.edu/faculty/Nemiroff.html
  32. http://www.phy.mtu.edu/
  33. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  34. http://www.astro.umd.edu/
  35. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  36. https://www.nasa.gov/about/highlights/HP_Privacy.html
  37. https://www.nasa.gov/general/accessibility/
  38. https://www.nasa.gov/privacy/
  39. https://astrophysics.gsfc.nasa.gov/
  40. https://www.nasa.gov/
  41. https://www.nasa.gov/centers/goddard/
  42. https://science.nasa.gov/learners
  43. http://www.mtu.edu/