Moons of Mars

property Deimos Phobos

mean distance from centre of planet

(orbital radius) 23,459 km 9,378 km

orbital period (sidereal period) 1.262 44 Earth days 0.318 91 Earth days

mean orbital velocity 1.4 km/s 2.1 km/s

inclination of orbit to planet's equator 1.79° 1.08°

eccentricity of orbit 0.0005 0.0151

rotation period* sync. sync.

radial dimensions 7.5 × 6.1 × 5.2 km 13.3 × 11.1 × 9.3 km

area 525 km² 1,625 km²

mass 1.8 × 10¹⁵ kg 1.08 × 10¹⁶ kg

mean density 1.8 grams/cm³ 1.9 grams/cm³

escape velocity 6 metres/s 10 metres/s

albedo 0.07 0.06

*sync. = synchronous rotation; the rotation and orbital periods are the same.