Launched July 22, 1962
Decommissioned March 16, 1975

The Mariner program consisted of 10 spacecraft launches into outer space over a 13-year period. Mariner I inaugurated the series in 1962; its mission was to reach the planet Venus. However, a computer error—a missing minus sign—caused the spacecraft to plunge into the Atlantic Ocean shortly after takeoff on July 22, 1962.

Mariner 2 was launched on August 27, becoming the first space mission to reach another planet. The 447-pound spacecraft took three and a half months to travel 35 million miles to Venus, passing as close as 22,000 miles to the planet on December 14. Mariner 2 sent back an enormous amount of information, confirming that the planet suffers from a super greenhouse effect: it is surrounded by dense layers of gases that keep heat from escaping, with temperatures reaching almost 900°F. It also discovered that, unlike Earth, Venus has no detectable magnetic field or radiation belts. The...