Following a string of failures, the Soviet Union would launch a probe that would eventually discover new scientific knowledge about the planet. And, that probe was launched on this day in history.
Venera 4 was launched by the Soviet Union on June 12th, 1967. The unmanned space probe would arrive at Venus in October. The probe entered the atmosphere of the planet as planned.
This was the first probe to analyze another planet in this way. Venera 4 was the first to analyze the composition of the atmosphere of Venus, finding it to mostly be made of carbon dioxide, with little oxygen. It also found extremely hot temperatures above 500 degrees and no water, despite thick cloud cover that blanketed the planet. The atmospheric pressure of the second planet of the solar system was found to be extremely heavy.
The mission was a success, and the Soviets would follow this success with the Venera 7 mission in 1970, which would be the first unmanned probe to land on Venus.