18th October 1967: Soviet spacecraft Venera 4 becomes the first to enter the atmosphere of Venus and transmit scientific data back to Earth

Scott Allsop (0:00)

On 18th October 1967, the Soviet spacecraft Venera 4 became the first to enter the atmosphere of Venus and transmit scientific data back to Earth. Welcome to HistoryPod.

Venus had proved a difficult planet to study from Earth as its surface was permanently hidden beneath thick clouds. While the earlier Venera 3 had struck Venus in 1966, making it the first human-made object to reach the surface of another planet, communications had failed before it could return scientific information. Its successor, Venera 4, was designed to overcome this problem by carrying instruments capable of measuring the atmosphere during its descent.

The mission was launched from the Baikonur Cosmodrome on 12th June. After travelling for 128 days, the capsule separated from the main spacecraft on 18th October and entered the atmosphere. After aerodynamic braking, a parachute was deployed and the capsule began its descent through the atmosphere. Instruments measured temperature, pressure and the composition of the surrounding gasses, with the results transmitted by radio to receiving stations on Earth. These transmissions continued for almost 94 minutes and revealed that the atmosphere was composed predominantly of carbon dioxide with very little water vapour. Temperatures and pressures increased rapidly as the probe descended, and the last transmission was received before the capsule had reached the planet's surface.

While the mission did not complete its intended soft landing, it did become the first to obtain direct measurements from the atmosphere of another planet. These showed that Venus was more hostile than some had previously suggested. The following day, NASA's Mariner 5 spacecraft reached Venus and conducted a flyby, collecting further information about the atmosphere. Despite ongoing Cold War tensions, scientists from the two countries later compared their results.