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 February 18
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                           Swiss Alps, Martian Sky
                 Image Credit & [3]Copyright: [4]Jens Bydal

   Explanation: [5]Taken on February 6, this snowy mountain and skyscape
   was captured near Melchsee-Frutt, central Switzerland, planet Earth.
   The reddish daylight and blue tinted glow around the afternoon Sun are
   [6]colors of the Martian sky, though. Of course [7]both worlds have the
   same Sun. From Mars, the Sun looks only about half as bright and 2/3
   the size compared to its appearance from Earth. Lofted from the surface
   of Mars, fine dust particles suspended in the thin Martian atmosphere
   are rich in the iron oxides that make the Red Planet red. They tend to
   absorb blue sunlight giving a red tinge to the [8]Martian sky, while
   forward scattering still makes the light appear relatively bluish near
   the smaller, fainter Martian Sun. Normally Earth's denser atmosphere
   strongly scatters blue light, making the terrestrial sky blue. But on
   February 6 a [9]huge cloud of dust blown across the Mediterranean from
   the Sahara desert reached the Swiss Alps, dimming the Sun and lending
   that Alpine afternoon the colors of the Martian sky. By the next day,
   only the snow was left covered with reddish dust.

               News from Mars: [10]NASA Perseverance Coverage
                    Tomorrow's picture: pixels from space
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    Authors & editors: [22]Robert Nemiroff ([23]MTU) & [24]Jerry Bonnell
                                 ([25]UMCP)
          NASA Official: Phillip Newman [26]Specific rights apply.
              [27]NASA Web Privacy Policy and Important Notices
                A service of: [28]ASD at [29]NASA / [30]GSFC
                           & [31]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2102/SwissAlpsMartianSky.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.astrobin.com/users/MrPhoton/
   5. https://www.astrobin.com/532fh5/?nc=user
   6. http://serious-science.org/what-color-is-the-sky-on-mars-7310
   7. https://apod.nasa.gov/apod/ap200802.html
   8. https://www.jpl.nasa.gov/images/a-moment-frozen-in-time
   9. https://earthobservatory.nasa.gov/images/146871/dust-traverses-the-atlantic-ocean
  10. https://mars.nasa.gov/mars2020/timeline/landing/watch-online/
  11. https://apod.nasa.gov/apod/ap210217.html
  12. https://apod.nasa.gov/apod/archivepix.html
  13. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  14. https://apod.nasa.gov/apod/lib/aptree.html
  15. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  16. https://apod.nasa.gov/apod/calendar/allyears.html
  17. https://apod.nasa.gov/apod.rss
  18. https://apod.nasa.gov/apod/lib/edlinks.html
  19. https://apod.nasa.gov/apod/lib/about_apod.html
  20. http://asterisk.apod.com/discuss_apod.php?date=210218
  21. https://apod.nasa.gov/apod/ap210219.html
  22. http://www.phy.mtu.edu/faculty/Nemiroff.html
  23. http://www.phy.mtu.edu/
  24. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  25. http://www.astro.umd.edu/
  26. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  27. https://www.nasa.gov/about/highlights/HP_Privacy.html
  28. https://astrophysics.gsfc.nasa.gov/
  29. https://www.nasa.gov/
  30. https://www.nasa.gov/centers/goddard/
  31. http://www.mtu.edu/