Mariner 10
September 21, 1974

 

Mercury's south pole

Mercury's south pole

 

Mercury is encountered a second time at a distance of 48,069 kilometers (29,870 miles).

Mariner 10, now orbiting the Sun, returns at six-month intervals for close mapping passes over the planet. Mercury's slow rotation leaves the other half always in the dark when Mariner 10 returns.