Moon of Jupiter, one of the Galeleian Moons.

Third largest moon in the solar system. The most heavily cratered object in the solar system, which is a title of dubious pride, I guess. The Valhalla crater is 3,000 km in diameter, which is a lot considering that the diameter of Callisto is 4,800 km.

Discovery:                             Jan 7, 1610 by Galileo Galilei
Diameter (km):                         4,806                 
Mass (kg):                             1.077e23  
Mass (Earth = 1)                       1,807e-2 
Surface Gravity (Earth = 1):           0.127
Mean Distance from Jupiter (km):       1,883,000
Mean Distance From Jupiter (Rj):       26,6
Mean Distance from Sun (AU):           5.203
Orbital period (days):                 16.68902 
Rotational period  (days):             16.68902 
Density (gm/cm3)                       1.86
Orbit Eccentricity:                    0.007
Orbit Inclination (degrees):           0.281
Orbit Speed (km/sec):                  8.21
Escape velocity (km/sec):              2.74 
Visual Albedo:                         ?
Subsolar Temperature (K):              ?
Equatorial Subsurface Temperature (K): ?
Surface Composition:                   Dirty Ice
Data from NASA