Closest approach to earth: 34,600,000 miles Mean distance from the sun: 141,600,000 miles Period of rotation around the sun: 1.88089 years Sideral rotation period: 24 hours, 37 minutes, 22.66 seconds Mean surface atmospheric temperature: -23 degrees Visual albedo: 0.159 Pole Star: BD 52, Degrees 2880 Visual magnitude at mean opposition: -2.01 Mass: 0.10174 Density: 3.93 Diameter: 0.