A Short History of the Exploration of Venus

Until the early 1960s, not much was known of Venus. Permanently shrouded by a layer of clouds, the second planet from the sun remained pretty much an enigma. It was thought to be about the same size and mass of the Earth, slightly warmer because it was closer to the Sun.

Scientists and science fiction writers imagined that Venus, of all the other planets of the Solar System, was most likely to contain life. Science fiction stories, up through the 1950s, imagined a Venus of lush jungles or of vast oceans teaming with life. There might even be intelligent beings waiting for the first Earth explorers.

It was therefore natural that the first interplanetary probe should be launched at Venus. On August 27th, 1962, the Mariner 2 space craft was launched on board an Atlas-Agena launch vehicle. Two days later, the Agena stage executed a second burn of its engines, placing the Mariner 2 in route for a flyby of Earth’s nearest neighbor.

The flyby occurred in December of 1962, with the Mariner 2 passing 34,773 kilometers from Venus at its closest approach. Far from a planet filled with life, Mariner 2 discovered a Venus with a surface temperature of eight hundred degrees Fahrenheit, an air pressure of ninety times Earth normal, a carbon dioxide atmosphere, no detectable magnetic field to shield the planet from cosmic radiation, and a permanent cloud bank at sixty kilometers above the surface. Venus rotation rate was slow, lasting about a normal Venusian year. Venus was, in effect, a Hell world where no life (at least as we know it) could possibly exist.

Nevertheless, other robotic space probes followed the Mariner 2. In 1967, the Mariner 5 flew by Venus, taking measurements of the Venusian atmosphere.  The Pioneer 12 reached Venus orbit in December, 1978 and spent over ten years studying Venus until it burned up in the Venusian atmosphere in 1992. The Pioneer 13 studied the composition of the planet’s atmosphere, the topography of its landscape, and the planet’s gravity field.