            APOD: 2018 May 7 - The Unusual Boulder at Tychos Peak

                         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 7
                                      [2]
                     The Unusual Boulder at Tycho's Peak
  Main Image Credit: NASA [3] , Arizona State U. [4] , LRO [5] ; Upper Inset:
NASA [6] , Arizona State U. [7] , LRO [8] ; Lower Inset: Gregory H. Revera [9]

Explanation: Why is there a large boulder near the center of Tycho's peak?
Tycho crater [10]  on the Moon [11]  is one of the easiest features to see,
visible [12]  even to the unaided eye (inset, lower right). But at the center
of Tycho [13]  (inset, upper left) is a something unusual -- a 120-meter
boulder. This boulder was imaged at very high resolution (link)at sunrise,
over the past decade, by the Moon-circling Lunar Reconnaissance Orbiter [14]
(LRO). The leading origin hypothesis is that that the boulder was thrown
during the tremendous collision [15]  that formed Tycho crater about 110
million years ago, and by chance came back down right near the center of the
newly-formed central mountain [16] . Over the next billion years meteor
impacts and moonquakes [17]  should slowly degrade Tycho [18] 's center,
likely causing the central boulder to tumble 2000 meters down to the crater
floor [19]  and disintegrate.

                      Tomorrow's picture: the seen [20]

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    Authors & editors: Robert Nemiroff [32] (MTU [33] ) & Jerry Bonnell [34]
                                  (UMCP [35] )
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Site notes:
  [1] archivepix.html
  [2] image/1805/TychoBoulder2_LRO_960.jpg
  [3] https://www.nasa.gov/
  [4] http://lroc.sese.asu.edu/
  [5] https://lro.gsfc.nasa.gov/
  [6] https://www.nasa.gov/
  [7] http://lroc.sese.asu.edu/
  [8] https://lro.gsfc.nasa.gov/
  [9] https://commons.wikimedia.org/wiki/File:FullMoon2010.jpg
  [10] https://en.wikipedia.org/wiki/Tycho_(lunar_crater)
  [11] ap180318.html
  [12] ap160201.html
  [13] https://www.nasa.gov/mission_pages/LRO/news/lro-tycho.html
  [14] https://lunar.gsfc.nasa.gov/about.html
  [15] ap140113.html
  [16] http://lroc.sese.asu.edu/posts/384
  [17]
https://science.nasa.gov/science-news/science-at-nasa/2006/15mar_moonquakes
  [18] https://www.youtube.com/watch?v=mfmQh_yDRBo
  [19]
https://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/
lroc-20100114-tycho.html
  [20] ap180508.html
  [21] ap180506.html
  [22] archivepix.html
  [23] lib/apsubmit2015.html
  [24] lib/aptree.html
  [25] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [26] calendar/allyears.html
  [27] /apod.rss
  [28] lib/edlinks.html
  [29] lib/about_apod.html
  [30] http://asterisk.apod.com/discuss_apod.php?date=180507
  [31] ap180508.html
  [32] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [33] http://www.phy.mtu.edu/
  [34] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [35] http://www.astro.umd.edu/
  [36] lib/about_apod.html#srapply
  [37] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [38] https://astrophysics.gsfc.nasa.gov/
  [39] https://www.nasa.gov/
  [40] https://www.nasa.gov/centers/goddard/
  [41] http://www.mtu.edu/
