Subj : Daily APOD Report
To   : All
From : Alan Ianson
Date : Sun Nov 28 2021 00:15:52

                        Astronomy Picture of the Day

    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.

                              2021 November 28

                 A High Cliff on Comet Churyumov-Gerasimenko
     Image Credit & Licence: ESA, Rosetta spacecraft, NAVCAM; Additional
                         Processing: Stuart Atkinson

   Explanation: This high cliff occurs not on a planet, not on a moon, but
   on a comet. It was discovered to be part of the dark nucleus of Comet
   Churyumov-Gerasimenko (CG) by Rosetta, a robotic spacecraft launched by
   ESA that rendezvoused with the Sun-orbiting comet in 2014. The ragged
   cliff, as featured here, was imaged by Rosetta in 2014. Although
   towering about one kilometer high, the low surface gravity of Comet CG
   would likely make it an accessible climb -- and even a jump from the
   cliff survivable. At the foot of the cliff is relatively smooth terrain
   dotted with boulders as large as 20 meters across. Data from Rosetta
   indicates that the ice in Comet CG has a significantly different
   deuterium fraction -- and hence likely a different origin -- than the
   water in Earth's oceans. Rosetta ended its mission with a controlled
   impact onto Comet CG in 2016. Comet CG has just completed another close
   approach to Earth and remains visible through a small telescope.

                    Tomorrow's picture: stellar pinwheel
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