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.

                                2023 July 31
    [2]A dark irregularly-shaped moon is seen in front of the red planet
   Mars. Craters are visible in the foreground and the edge of the planet
   is just visible at the top of the image. Please see the explanation for
                         more detailed information.

                              Phobos over Mars
   Image Credit: [3]ESA, [4]DLR, [5]FU Berlin, [6]Mars Express; Processing
                   & [7]CC BY 2.0 License: [8]Andrea Luck

   Explanation: Why is Phobos so dark? [9]Phobos, the largest and
   innermost of the two Martian moons, is the darkest moon in the entire
   [10]Solar System. Its unusual orbit and color indicate that it may be a
   captured [11]asteroid composed of a mixture of ice and dark rock. The
   [12]featured assigned-color picture of Phobos near the edge of [13]Mars
   was captured in late 2021 by [14]ESA's robot spacecraft [15]Mars
   Express, currently orbiting Mars. [16]Phobos is a heavily cratered and
   [17]barren moon, with its [18]largest crater located on the far side.
   From images like this, [19]Phobos has been determined to be covered by
   perhaps a meter of [20]loose dust. Phobos [21]orbits so close to Mars
   that from some places it would appear to rise and set twice a day,
   while from other places it would [22]not be visible at all. [23]Phobos'
   orbit around Mars is continually decaying -- it will likely [24]break
   up with pieces crashing to the Martian surface in about 50 million
   years.

   Your Sky Surprise: [25]What picture did APOD feature on your birthday?
                                 (post 1995)
                Tomorrow's picture: monster at the Sun's edge
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    Authors & editors: [37]Robert Nemiroff ([38]MTU) & [39]Jerry Bonnell
                                 ([40]UMCP)
          NASA Official: Phillip Newman [41]Specific rights apply.
              [42]NASA Web Privacy Policy and Important 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/2307/PhobosMars_MarsExpress_1500.jpg
   3. https://www.esa.int/
   4. https://www.dlr.de/EN/organisation-dlr/dlr/dlr-at-a-glance.html
   5. https://www.fu-berlin.de/
   6. https://www.esa.int/Science_Exploration/Space_Science/Mars_Express
   7. https://creativecommons.org/licenses/by/2.0/
   8. https://twitter.com/andrluck
   9. https://solarsystem.nasa.gov/moons/mars-moons/phobos/in-depth/
  10. https://solarsystem.nasa.gov/planets/overview/
  11. https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/overview/
  12. https://www.flickr.com/photos/192271236@N03/53063793187/in/pool-apods/
  13. https://solarsystem.nasa.gov/planets/mars/overview/
  14. https://www.esa.int/
  15. https://www.esa.int/Science_Exploration/Space_Science/Mars_Express
  16. https://apod.nasa.gov/apod/ap080414.html
  17. https://apod.nasa.gov/apod/ap031109.html
  18. https://apod.nasa.gov/apod/ap230708.html
  19. https://apod.nasa.gov/apod/ap061203.html
  20. https://apod.nasa.gov/apod/ap980914.html
  21. http://www.youtube.com/watch?v=7rxqZcO-0uI
  22. https://img.jagranjosh.com/images/2023/June/2062023/find-the-cat-in-leaves.jpg
  23. https://en.wikipedia.org/wiki/Phobos_(moon)
  24. https://ui.adsabs.harvard.edu/abs/2008AGUFM.P51C1423H/abstract
  25. https://apod.nasa.gov/apod/calendar/allyears.html
  26. https://apod.nasa.gov/apod/ap230730.html
  27. https://apod.nasa.gov/apod/archivepix.html
  28. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  29. https://apod.nasa.gov/apod/lib/aptree.html
  30. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  31. https://apod.nasa.gov/apod/calendar/allyears.html
  32. https://apod.nasa.gov/apod.rss
  33. https://apod.nasa.gov/apod/lib/edlinks.html
  34. https://apod.nasa.gov/apod/lib/about_apod.html
  35. https://asterisk.apod.com/discuss_apod.php?date=230731
  36. https://apod.nasa.gov/apod/ap230801.html
  37. http://www.phy.mtu.edu/faculty/Nemiroff.html
  38. http://www.phy.mtu.edu/
  39. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  40. http://www.astro.umd.edu/
  41. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  42. https://www.nasa.gov/about/highlights/HP_Privacy.html
  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/