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.

                                2020 August 2

                             Two Worlds, One Sun
                 Left Image Credit & Copyright: Damia Bouic;
   Right Image Credit: NASA, JPL-Caltech, MSSS; Digital processing: Damia
                                    Bouic

   Explanation: How different does sunset appear from Mars than from
   Earth? For comparison, two images of our common star were taken at
   sunset, one from Earth and one from Mars. These images were scaled to
   have same angular width and featured here side-by-side. A quick
   inspection will reveal that the Sun appears slightly smaller from Mars
   than from Earth. This makes sense since Mars is 50% further from the
   Sun than Earth. More striking, perhaps, is that the Martian sunset is
   noticeably bluer near the Sun than the typically orange colors near the
   setting Sun from Earth. The reason for the blue hues from Mars is not
   fully understood, but thought to be related to forward scattering
   properties of Martian dust. The terrestrial sunset was taken in 2012
   March from Marseille, France, while the Martian sunset was captured in
   2015 by NASA's robotic Curiosity rover from Gale crater on Mars. Last
   week a new rover and a helicopter -- onboard Mars 2020 -- launched for
   Mars.

                      Tomorrow's picture: gaping comet
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.

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