First Flyby of Mercury

March 29, 1974

Mariner 10 becomes the first spacecraft to flyby the planet Mercury. At a range of 437 miles, Mariner 10 was able to send back the first close up images of Mercury indicating a Moon-like surface of craters and ridges. Until Mariner ran out of fuel and contact terminated about one year later, it made two more flybys of Mercury returning over 2,700 pictures of the innermost planet in our solar system.

Mariner 10 also was famous for many other firsts:

• The first spacecraft to use the gravity of one planet (Venus) to reach another (Mercury)
• The first spacecraft to return data on a long-period comet (Kohoutek)
• The first mission to explore two planets (Mercury and Venus) during a single mission
• The first spacecraft to use a gravity assist to change its flight path
• The first spacecraft to return to its target after an initial encounter
• The first probe to use the solar wind as a major means of spacecraft orientation during flight