                      APOD: 2018 May 5 - Stickney Crater

                         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 May 5
                                      [2]
                               Stickney Crater
     Image Credit: HiRISE [3] , MRO [4] , LPL (U. Arizona) [5] , NASA [6]

Explanation: Stickney Crater, the largest crater on the martian moon Phobos,
is named for Chloe Angeline Stickney [7]  Hall, mathematician and [8]  wife of
astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons [9]
in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of
Phobos itself, so large that the impact that blasted out the crater likely
came close to shattering the tiny moon. This stunning, enhanced-color image
[10]  of Stickney and surroundings was recorded by the HiRISE camera onboard
the Mars Reconnaissance Orbiter as it passed within some six thousand
kilometers of Phobos [11]  in March of 2008. Even though the surface gravity
of asteroid-like Phobos [12] is less than 1/1000th Earth's gravity, streaks
suggest loose material slid down inside the crater walls over time. Light
bluish regions near the crater's rim could indicate a relatively freshly
exposed surface. The origin of the curious grooves [13]  along the surface is
mysterious but may be related to the crater-forming impact [14] .

                       Follow: Mars InSight Launch [15]
                      Tomorrow's picture: sky canyon [16]

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Site notes:
  [1] archivepix.html
  [2] image/1805/PSP_007769_9010_IRB_Stickney.jpg
  [3] http://hirise.lpl.arizona.edu/
  [4] http://mars.jpl.nasa.gov/mro/
  [5] http://www.lpl.arizona.edu/
  [6] http://www.nasa.gov/
  [7] http://en.wikipedia.org/wiki/Angeline_Stickney
  [8] https://archive.org/details/anastronomerswi03hallgoog
  [9] ap031024.html
  [10] http://hirise.lpl.arizona.edu/phobos.php
  [11] ap170721.html
  [12] https://solarsystem.nasa.gov/moons/mars-moons/phobos/ in-depth/
  [13] ap041120.html
  [14] http://adsabs.harvard.edu/abs/2016GeoRL..4310595B
  [15] https://mars.nasa.gov/insight/mission/timeline/launch/
  [16] ap180506.html
  [17] ap180504.html
  [18] archivepix.html
  [19] lib/apsubmit2015.html
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  [26] http://asterisk.apod.com/discuss_apod.php?date=180505
  [27] ap180506.html
  [28] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [29] http://www.phy.mtu.edu/
  [30] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
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