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 July 6
    [2]A computer construction of what the north pole of Mars looks like.
      The picture was constructed from measured altitude data. A spiral
   landscape is seen that is colored red but is mostly covered with white
       ice. Please see the explanation for more detailed information.

                        The Spiral North Pole of Mars
      Image Credit: [3]ESA/[4]DLR/[5]FU Berlin; [6]NASA [7]MGS [8]MOLA
                                Science Team

   Explanation: Why is there a spiral around the North Pole of Mars? Each
   winter [9]this pole develops a new outer layer about one meter thick
   composed of [10]carbon dioxide frozen out of the thin Martian
   atmosphere. This [11]fresh layer is deposited on a water-ice layer that
   exists year round. Strong [12]winds blow down from above the cap's
   center and swirl due to the spin of [13]the red planet -- contributing
   to [14]Planum Boreum's spiral structure. The [15]featured image is a
   perspective mosaic generated in 2017 from numerous images taken by
   ESA's [16]Mars Express and elevations extracted from the [17]laser
   altimeter aboard NASA's [18]Mars Global Surveyor mission.

                       Tomorrow's picture: alien comet
     __________________________________________________________________

      [19]< | [20]Archive | [21]Submissions | [22]Index | [23]Search |
   [24]Calendar | [25]RSS | [26]Education | [27]About APOD | [28]Discuss |
                                    [29]>
     __________________________________________________________________

    Authors & editors: [30]Robert Nemiroff ([31]MTU) & [32]Jerry Bonnell
                                 ([33]UMCP)
          NASA Official: Amber Straughn [34]Specific rights apply.
            [35]NASA Web Privacy, [36]Accessibility, [37]Notices;
                A service of: [38]ASD at [39]NASA / [40]GSFC,
                         [41]NASA Science Activation
                           & [42]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2507/MarsNorthPole_MarsExpress_960.jpg
   3. http://www.esa.int/
   4. http://www.dlr.de/pf/
   5. http://www.fu-berlin.de/
   6. https://www.nasa.gov/
   7. https://mars.nasa.gov/programmissions/missions/past/globalsurveyor/
   8. https://attic.gsfc.nasa.gov/mola/
   9. https://apod.nasa.gov/apod/ap981216.html
  10. https://science.nasa.gov/resource/dry-ice-on-mars/
  11. https://www.reddit.com/media?url=https://preview.redd.it/after-weeks-of-introduction-my-two-cats-are-sleeping-just-a-v0-dmmx64eawrgc1.jpeg?width=4032&format=pjpg&auto=webp&s=0daba0c545383f1db06d3eec762ec9ba42cc8caa
  12. https://en.wikipedia.org/wiki/Katabatic_wind
  13. https://science.nasa.gov/mars/
  14. https://en.wikipedia.org/wiki/Planum_Boreum
  15. http://www.esa.int/spaceinimages/Images/2017/02/Perspective_view_of_Mars_north_polar_ice_cap
  16. https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_science_highlights
  17. https://ilrs.gsfc.nasa.gov/lw16/docs/presentations/sci_6_Smith.pdf
  18. https://science.nasa.gov/mission/mars-global-surveyor/
  19. https://apod.nasa.gov/apod/ap250705.html
  20. https://apod.nasa.gov/apod/archivepix.html
  21. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  22. https://apod.nasa.gov/apod/lib/aptree.html
  23. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  24. https://apod.nasa.gov/apod/calendar/allyears.html
  25. https://apod.com/feed.rss
  26. https://apod.nasa.gov/apod/lib/edlinks.html
  27. https://apod.nasa.gov/apod/lib/about_apod.html
  28. https://asterisk.apod.com/discuss_apod.php?date=250706
  29. https://apod.nasa.gov/apod/ap250707.html
  30. http://www.phy.mtu.edu/faculty/Nemiroff.html
  31. http://www.phy.mtu.edu/
  32. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  33. http://www.astro.umd.edu/
  34. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  35. https://www.nasa.gov/about/highlights/HP_Privacy.html
  36. https://www.nasa.gov/general/accessibility/
  37. https://www.nasa.gov/privacy/
  38. https://astrophysics.gsfc.nasa.gov/
  39. https://www.nasa.gov/
  40. https://www.nasa.gov/centers/goddard/
  41. https://science.nasa.gov/learners
  42. http://www.mtu.edu/