Phobos (or M1 Phobos) is the first satellite of Mars.  The
    following properties are from K.R. Lang, 'Astrophysical Data:
    Planets and Stars', pp.70-73:
 
      Distance from planet center:     9.37e03    km
                                       2.76       planet radii
                   Orbital period:     0.3189     days
                     Eccentricity:     0.0150     degrees
                      Inclination:     1.1        degrees
 
                           Radius:     14 x 10    km
                             Mass:     9.6e-5     1.e23 grams
                          Density:  <= 2          grams/cm^3
               Visual Magnitude
                    at Opposition:    11.6
                 at Unit Distance:   +11.9
          Geometric Visual Albedo:     0.06