As the innermost and smallest planet in our solar system, Mercury is a uniquely fascinating place, so it’s no wonder it was one of the earliest targets for spaceflight. NASA’s Mariner 10 probe, launched 43 years ago on November 3, 1973, was the explorer that finally pulled this ambitious dream into reality.
Not only was it the first spacecraft with multiple planetary stops—Venus and Mercury—it was also the first mission to use the gravitational pull of a planet to propel it onward to a new destination. These gravity slingshot maneuvers have become an essential tool for scooting around the solar system, a convenience we owe to Mariner 10’s trailblazing acrobatics some four decades ago. … (Motherboard)