As Mariner 10 approached Mercury at nearly seven miles per second on March 29, it's TV camera took this picture (FDS 27371) from an altitude of 35,000 kilometers (21,700 miles) The picture shows a heavily-cratered surface with many low hills. The large valley to the right is seven kilometers (4 1/2 miles) wide and more than 100 kilometers (62 miles) long. The large flat-floored crater near the right is about 80 kilometers (50 miles) in diameter.
The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.