Mariner 10 - The Mariner 10 spacecraft launched on November 3, 1973. Mariner 10 was the first spacecraft to use a gravity assist trajectory, accelerating as it entered the gravitational influence of Venus, then being flung by the planet's gravity onto a slightly different course to reach Mercury. It was also the first spacecraft to encounter two planets at close range. Mercury - Known as the planet closet to the sun, Mercury is a dense and rocky planet. Discover here more intriguing facts about Mercury.
Materials here reveal facts, missions, and educational resources about Mars.
Read here to learn more about Venus. Voyager - Twin spacecraft Voyager 1 and Voyager 2 were launched by NASA during the summer of 1977 from Cape Canaveral, Florida. Barring any serious spacecraft subsystem failures, the Voyagers may survive and relay data from the outer planets until the early twenty-first century. Learn more about the historical study of Mercury at this site. This document is in PDF format and requires the Adobe Acrobat reader software .