Earth's, is its mass, expressed as a multiple of the Earth's mass and its radius, expressed as a multiple of the Earth's (mean) radius (6,371 km). For instance, Mars has a mass of = 0.107 Earth masses and a mean radius of 3,390 km = 0.532 Earth radii. The surface gravity of Mars is therefore approximately

times that of Earth. Without using the Earth as a reference body, the surface gravity may also be