Goals: Venera 4 was designed to analyze the atmosphere of Venus while descending through it.
Accomplishments: Venera 4 released its atmospheric probe as planned, moments before the main spacecraft hit the atmosphere and was destroyed. The probe parachuted down, collecting and transmitting data for 93 minutes until, at an altitude of about 25 km, the planet's enormous atmospheric pressure crushed it.
The data that Venera 4 returned to Earth indicated that at the planet's surface, the temperature was 500 degrees Celsius and the atmospheric pressure was 75 times that of Earth. Conducting the first direct sampling of the atmosphere, the probe's gas analyzers found that it was 90 to 95 percent carbon dioxide with no nitrogen and small amounts of oxygen and water vapor.