Earths) Mass 8.9319 × 10 22  kg (0.015 Earths)Mean  density 3.528 g/cm 3 Equatorial surface gravity 1.796  m/s 2  (0.183  g ) Escape velocity 2.558 km/s Rotation period synchronous Equatorial rotation velocity271 km/h Albedo 0.63 ± 0.02 [3] Surface  temp.     Surface min mean max 90  K 110  K 130 K [5] Apparent magnitude 5.02 ( opposition