Mathilde

Asteroid 253, which was imaged by the Near-Earth Asteroid Rendezvous (NEAR) mission in a close flyby on 27 June 1997. Mathilde is a uniformly dark C-type asteroid with an albedo of only 3 per cent. NEAR found its mean diameter to be 52 km (33 miles). Five craters with diameters in excess of 20 km (12 miles) were identified on the side of the asteroid in sunlight at the time of the encounter. Its rotation period was also measured and found to be unexpectedly long at 17.4 days.