Astronomy Picture of the Day

                         Astronomy Picture of the Day

    Discover the cosmos! [1] Each day a different image or photograph of our
 fascinating universe is featured, along with a brief explanation written by a
                           professional astronomer.

                               2018 November 25
                                      [2]
                         Phobos: Doomed Moon of Mars
  Image Credit: Viking Project [3] , JPL [4] , NASA [5] ; Mosaic Processing:
              Edwin V. Bell II (NSSDC [6] / Raytheon [7]  ITSS)

Explanation: This moon is doomed. Mars [8] , the red planet named for the
Roman god of war [9] , has two tiny moons, Phobos [10]  and Deimos [11] ,
whose names are derived from the Greek for Fear and Panic [12] . The origin of
the Martian moons is unknown, though, with a leading hypothesis holding that
they are captured asteroids [13] . The larger moon, at 25-kilometers across,
is Phobos [14] , and is indeed seen to be a cratered, asteroid-like object in
this false-colored image [15]  mosaic taken by the robotic Viking 1 mission in
1978. A recent analysis [16]  of the unusual long grooves seen on Phobos [17]
indicates that they may result from boulders rolling away from the giant
impact that created the crater on the upper left: Stickney Crater [18] .
Phobos [19] orbits so close to Mars - about 5,800 kilometers above the surface
compared to 400,000 kilometers for our Moon [20]  - that gravitational tidal
force [21] s are dragging it down. The ultimate result will be for Phobos to
break up [22]  in orbit and then crash down onto the Martian surface in about
50 million years. Well before that -- tomorrow, in fact, if everything goes
according to plan -- NASA's robotic InSight lander will touch down [23]  on
Mars and begin investigating its internal structure.

                Latest: Insight to Land on Mars Tomorrow [24]
                     Tomorrow's picture: up, up, and away

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    Authors & editors: Robert Nemiroff [36] (MTU [37] ) & Jerry Bonnell [38]
                                  (UMCP [39] )
          NASA Official:  Phillip Newman Specific rights apply [40] .
              NASA Web Privacy Policy and Important Notices [41]
              A service of: ASD [42]  at NASA [43]  / GSFC [44]
                           & Michigan Tech. U. [45]
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Site notes:
  [1] archivepix.html
  [2] image/1811/Phobos_Viking1_1175.jpg
  [3] https://mars.nasa.gov/programmissions/mission...
  [4] https://www.jpl.nasa.gov/
  [5] https://www.nasa.gov/
  [6] https://nssdc.gsfc.nasa.gov/
  [7] https://www.raytheon.com/
  [8] http://mars.jpl.nasa.gov/allaboutmars/extreme...
  [9] https://en.wikipedia.org/wiki/Mars_(mythology...
  [10] https://solarsystem.nasa.gov/moons/mars-moons...
  [11] https://solarsystem.nasa.gov/moons/mars-moons...
  [12]
http://1.bp.blogspot.com/-yzPdCk_Kc30/UcsbcNx...
s1600/scared_cat_is_really_scared-e1349731123898.jpg
  [13]
https://solarsystem.nasa.gov/asteroids-comets...
  [14] ap030329.html
  [15]
https://nssdc.gsfc.nasa.gov/photo_gallery/cap...
  [16] https://news.brown.edu/articles/2018/11/phobo...
  [17] ap151122.html
  [18] ap180505.html
  [19] http://www.youtube.com/watch?v=IHDH7cKX_SA
  [20] ap020504.html
  [21] https://en.wikipedia.org/wiki/Tidal_force
  [22] https://en.wikipedia.org/wiki/Phobos_(moon)#P...
  [23] https://www.nasa.gov/feature/jpl/nasa-insight...
  [24] https://twitter.com/NASAInSight
  [25] ap181124.html
  [26] archivepix.html
  [27] lib/apsubmit2015.html
  [28] lib/aptree.html
  [29] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apo...
  [30] calendar/allyears.html
  [31] /apod.rss
  [32] lib/edlinks.html
  [33] lib/about_apod.html
  [34] http://asterisk.apod.com/discuss_apod.php?dat...
  [35] ap181126.html
  [36] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [37] http://www.phy.mtu.edu/
  [38] https://antwrp.gsfc.nasa.gov/htmltest/jbonnel...
  [39] http://www.astro.umd.edu/
  [40] lib/about_apod.html#srapply
  [41] https://www.nasa.gov/about/highlights/HP_Priv...
  [42] https://astrophysics.gsfc.nasa.gov/
  [43] https://www.nasa.gov/
  [44] https://www.nasa.gov/centers/goddard/
  [45] http://www.mtu.edu/

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