The Moons of Mars

Mars has two small, irregular Moons: Phobos and Deimos. They are apparently quite similar in composition but their surfaces are distinct in character. One of the main differences between the two moons is the presence on Phobos of large "grooves" with no counterpart on Deimos.

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• Some dynamical characteristics of Phobos and Deimos
• Comparison between Phobos and Deimos
• Craters of Phobos and Deimos

Some dynamical characteristics of Phobos and Deimos :

                               Phobos                           Deimos
Orbital parameters  (km)       9378.5                           23.459
Period                         7h 39 mn                         30h 18mn
Mass (kg)                      1.08 (+/- 0.01) x 106            1.80 (+/-0.15) x 1015
Axes (km)                      13.4 (+/-0.4) x (11+/-0.2)       7.5 (+/- 0.3) x 6.1 (+/- 0.3)
                                 x 9.2 (+/- 0.1)                    x 5.2 (+/-0.2)

Comparison between Phobos and Deimos

                              Phobos                            Deimos

Similarities
Albedo                        0.05+/-0.01                       0.06+/-0.01
Spectral Reflectance          type C                            type C
Mean density (g.cm-3 )        2.2 (+/-0.5)                      1.7 (+/- 0.5)
Surface thermal inerty
(10-3cal.cm-2.s-1/2K-1)       0.6-2.0                           0.9-1.6

Differences
Craterization density          High                             Less high
Crater ejecta dispersion       Local                            Widely spreaded
Regolith gravity motion        Local                            Global
Tectonic/Structure             Global groove system             No groove but ridges

Dimensions of the larger crater of Phobos and Deimos

Diameter          Phobos                     Deimos
                  Stickney  10  km           2,3 km
                  Hall  5
                  Roche  5