ABSTRACT
Mariner 10 was launched on 3 November 1973; it bypassed Venus on the foUov-ri.ng 4 February and then swung in to rendezvous with Mercury, making three active passes before its power failed.
The first of these was on 29 March 1974, the second on 21 September 1974 and the third on 16 March 1975. Almost half the surface of the planet \vas mapped, and showed it to be superficially very like that of the Moon, with mountains, craters, valleys and ridges. Contact was finally lost on 24 March 1975, though no doubt Mariner is still in solar orbit and stilJ making regular close passes of Mercury.
