Goals: This mission, like its twin Venera 12, called for a flyby spacecraft and a lander to explore Venus' ionosphere, atmosphere and surface and the interplanetary environment.
Accomplishments: The flyby craft studied the solar wind, gamma-ray bursts, ultraviolet radiation, and Venus' ionosphere. It passed the planet at a distance of about 35,000 km (about 22,000 miles). The lander probed Venus' atmosphere as it descended and then transmitted data from the surface for 95 minutes. Its camera system and soil-analysis experiment failed, but the mission did report evidence of lightning and thunder, carbon monoxide at low altitudes, and data on isotopes of argon that prompted scientists to question the theory that the original atmospheres of Venus, Earth and Mars were the result of outgassing from volcanoes.