Venera 4

Venera 4 (Russian: Венера-4, Венера meaning Venus; manufacturer's designation: 1V (V-67)) was a probe in the Soviet Venera program for the exploration of Venus. Venera-4 was the first successful probe to perform in-place analysis of the environment of another planet. It was also the first probe to land on another planet. Venera 4 provided the first chemical analysis of the Venusian atmosphere, showing it to be primarily carbon dioxide with a few percent of nitrogen and below one percent of oxygen and water vapors. The station detected a weak magnetic field and no radiation field. The outer atmospheric layer contained very little hydrogen and no atomic oxygen. The probe sent the first direct measurements proving that Venus was extremely hot, that the atmosphere was far denser than expected, and that Venus had lost most of its water long ago.