            APOD: 2017 December 19 - The Spiral North Pole of Mars

                         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 December 19
                                      [2]
                        The Spiral North Pole of Mars
  Image Credit: ESA [3] / DLR [4] / FU Berlin [5] ; NASA [6] MGS [7] MOLA [8]
                                 Science Team

Explanation: Why is there a spiral around the North Pole of Mars? Each winter
this pole [9] develops a new outer layer about one meter thick composed of
carbon dioxide frozen [10]  out of the thin Martian atmosphere. This fresh
layer is deposited on a water-ice layer that exists year round. Strong winds
blow down [11] from above the cap's center and swirl due to the spin of the
red planet [12]  -- contributing to Planum Boreum [13] 's spiral structure.
The featured image [14]  is a perspective mosaic generated earlier this year
from numerous images taken by ESA's Mars Express [15]  and elevations
extracted from the laser altimeter [16]  aboard NASA's Mars Global Surveyor
[17]  mission. New missions to Mars planned in the next few years include
Insight [18] with plans to drill into Mars, and ExoMars [19] and the Mars 2020
Rover [20] with plans to search for signs of microscopic Martian life [21]  --
past and present.

         Free APOD Lectures: January 5 in NYC & January 9 in DC [22]
                 Tomorrow's picture: vertical space hair [23]

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    Authors & editors: Robert Nemiroff [35] (MTU [36] ) & Jerry Bonnell [37]
                                  (UMCP [38] )
          NASA Official:  Phillip Newman Specific rights apply [39] .
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              A service of: ASD [41]  at NASA [42]  / GSFC [43]
                           & Michigan Tech. U. [44]
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Site notes:
  [1] archivepix.html
  [2] image/1712/MarsNorthPole_MarsExpress_1110.jpg
  [3] http://www.esa.int/
  [4] http://www.dlr.de/pf/
  [5] http://www.fu-berlin.de/
  [6] https://www.nasa.gov/
  [7] https://mars.nasa.gov/programmissions/missions/past/globalsurveyor/
  [8] https://attic.gsfc.nasa.gov/mola/
  [9] ap981216.html
  [10] https://www.youtube.com/watch?v=n0362IqnMXY
  [11] https://en.wikipedia.org/wiki/Katabatic_wind
  [12] ap160529.html
  [13] https://en.wikipedia.org/wiki/Planum_Boreum
  [14]
http://www.esa.int/spaceinimages/Images/2017/02/
Perspective_view_of_Mars_north_polar_ice_cap
  [15]
http://www.esa.int/Our_Activities/Space_Science/Mars_Express/
Mars_Express_mission_facts
  [16] https://mars.nasa.gov/MPF/martianchronicle/martianchron3/marschro35.html
  [17] https://en.wikipedia.org/wiki/Mars_Global_Surveyor
  [18] https://insight.jpl.nasa.gov/home.cfm
  [19] http://exploration.esa.int/mars/46048-programme-overview/
  [20] https://mars.nasa.gov/mars2020/mission/rover/
  [21] https://mars.nasa.gov/programmissions/overview/
  [22] http://asterisk.apod.com/viewtopic.php?f=28&t=37750
  [23] ap171220.html
  [24] ap171218.html
  [25] archivepix.html
  [26] lib/apsubmit2015.html
  [27] lib/aptree.html
  [28] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [29] calendar/allyears.html
  [30] /apod.rss
  [31] lib/edlinks.html
  [32] lib/about_apod.html
  [33] http://asterisk.apod.com/discuss_apod.php?date=171219
  [34] ap171220.html
  [35] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [36] http://www.phy.mtu.edu/
  [37] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [38] http://www.astro.umd.edu/
  [39] lib/about_apod.html#srapply
  [40] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [41] https://astrophysics.gsfc.nasa.gov/
  [42] https://www.nasa.gov/
  [43] https://www.nasa.gov/centers/goddard/
  [44] http://www.mtu.edu/
