On this day in 1962 NASA launched its Mariner 2 probe aboard a two-stage Atlas rocket. On its journey to its destination, Venus, the probe took measurements of interplanetary dust and the Solar wind. When Mariner 2 flew by Venus on 14 December, its radiometers determined that the planet is shrouded in thick, relatively cool clouds -- which implied that the planet's surface is much hotter. Mariner 2 was the first robotic space probe to conduct a successful planetary encounter.
