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 November 8

                    Martian Moon Phobos from Mars Express
     Image Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA;
                        Acknowledgement: Peter Masek

   Explanation: Why is Phobos so dark? Phobos, the largest and innermost
   of two Martian moons, is the darkest moon in the entire Solar System.
   Its unusual orbit and color indicate that it may be a captured asteroid
   composed of a mixture of ice and dark rock. The featured picture of
   Phobos near the limb of Mars was captured in 2010 by the robot
   spacecraft Mars Express currently orbiting Mars. Phobos is a heavily
   cratered and barren moon, with its largest crater located on the far
   side. From images like this, Phobos has been determined to be covered
   by perhaps a meter of loose dust. Phobos orbits so close to Mars that
   from some places it would appear to rise and set twice a day, but from
   other places it would not be visible at all. Phobos' orbit around Mars
   is continually decaying -- it will likely break up with pieces crashing
   to the Martian surface in about 50 million years.

                    Tomorrow's picture: in green company
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
                NASA Web Privacy Policy and Important Notices
                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.

--- hpt/lnx 1.9.0