From The Archives: 50 Years Ago In Aviation Week

NASA’s Mariner 10 spacecraft had already reached Mercury’s vicinity when this composite image of cloud cover on Venus, recorded from the robotic probe in invisible ultraviolet light, appeared on our April 8, 1974, cover. 

From the NASA Jet Propulsion Laboratory, future Editor-in-Chief Donald E. Fink reported that a March 29 flyby of Mercury collected an “enormous scientific yield,” including the first high-resolution television pictures of the planet’s heavily cratered, moon-like surface. 

Mariner 10, launched in November 1973 and the last of the Mariner missions, was the first spacecraft to visit Mercury, the first to explore two planets (Venus and Mercury), the first to use a gravity assist to change its flightpath and the first to use solar wind as the major means of spacecraft orientation. 

Looping around the Sun, it would make two return flybys of Mercury, the last on March 16, 1975, when it came within 200 mi. of the planet’s surface.