            APOD: 2017 July 23 - Mercury as Revealed by MESSENGER

                         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.

                                 2017 July 23
                                      [2]
                      Mercury as Revealed by MESSENGER
        Image Credit: MESSENGER [3] , NASA [4] , JHU APL [5] , CIW [6]

Explanation: Mercury had never been seen like this before. In 2008, the
robotic MESSENGER spacecraft [7]  buzzed past Mercury [8] for the second time
and imaged terrain mapped previously only by comparatively crude radar [9] .
The featured image [10]  was recorded as MESSENGER [11]  looked back 90
minutes after passing, from an altitude of about 27,000 kilometers. Visible in
the image, among many other newly imaged features, are unusually long rays
[12]  that appear to run like meridians [13]  of longitude [14] out from a
young crater near the northern limb. MESSENGER [15]  entered orbit around
Mercury in 2011 and finished its primary mission in 2012, but took detailed
measurements [16]  until 2015, at which time it ran out of fuel and so was
instructed to impact Mercury's surface [17] .

    New Moon Tonight: The next New Moon will block the Sun. [18]  Tomorrow's
                         picture: hybrid eclipse [19]

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    Authors & editors: Robert Nemiroff [31] (MTU [32] ) & Jerry Bonnell [33]
                                  (UMCP [34] )
          NASA Official:  Phillip Newman Specific rights apply [35] .
              NASA Web Privacy Policy and Important Notices [36]
              A service of: ASD [37]  at NASA [38]  / GSFC [39]
                           & Michigan Tech. U. [40]
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Site notes:
  [1] archivepix.html
  [2] image/1707/mercuryflyby2_messenger_1024.png
  [3] http://messenger.jhuapl.edu/About/Team.html
  [4] https://www.nasa.gov/
  [5] http://www.jhuapl.edu/
  [6] http://www.ciw.edu/
  [7]
https://en.wikipedia.org/wiki/MESSENGER#/media/
File:MESSENGER_-_spacecraft_at_mercury_-_atmercury_lg.jpg
  [8] http://en.wikipedia.org/wiki/Mercury_(planet)
  [9] http://adsabs.harvard.edu/abs/2007SSRv..132..307H
  [10] https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2004-030A
  [11] https://apod.nasa.gov/cgi-bin/apod/apod_search?tquery=MESSENGER
  [12] ap080204.html
  [13] http://www.csulb.edu/~rodrigue/geog140/lectures/geographicgrid.html
  [14]
http://www.independent.co.uk/news/science/
john-harrisons-longitude-clock-sets-new-record-300-years-on-10187304.html
  [15] http://en.wikipedia.org/wiki/MESSENGER
  [16] https://www.youtube.com/watch?v=ENwD31EDFjc
  [17] ap150501.html
  [18] https://eclipse2017.nasa.gov/
  [19] ap170724.html
  [20] ap170722.html
  [21] archivepix.html
  [22] lib/apsubmit2015.html
  [23] lib/aptree.html
  [24] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [25] calendar/allyears.html
  [26] /apod.rss
  [27] lib/edlinks.html
  [28] lib/about_apod.html
  [29] http://asterisk.apod.com/discuss_apod.php?date=170723
  [30] ap170724.html
  [31] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [32] http://www.phy.mtu.edu/
  [33] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [34] http://www.astro.umd.edu/
  [35] lib/about_apod.html#srapply
  [36] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [37] https://astrophysics.gsfc.nasa.gov/
  [38] https://www.nasa.gov/
  [39] https://www.nasa.gov/centers/goddard/
  [40] http://www.mtu.edu/
