Venera 8

Lore & Background

Venera 8 took 117 days to reach Venus with one mid-course correction on 6 April 1972. It separated from the bus, which contained a cosmic ray detector, solar wind detector, and ultraviolet spectrometer, and entered the atmosphere on 22 July 1972 at 08:37 UT. A refrigeration system attached to the bus pre-chilled the descent capsule's interior prior to atmospheric entry to prolong its life on the surface. Descent speed was reduced from 41,696 km/h to about 900 km/h by atmospheric drag deceleration, and the 2.5 meter diameter parachute opened at an altitude of 60 km.

During descent, Venera 8 transmitted data. A sharp decrease in illumination was noted at 35 to 30 km altitude, and wind speeds of less than 1 m/s were measured below 10 km. The lander touched down in what is now called Vasilisa Regio, within 150 km radius of 10.70°S 335.25°E, in sunlight, about 500 km from the morning terminator.

The lander continued to send back data for 50 minutes, 11 seconds after landing before failing due to harsh surface conditions. It confirmed the earlier data on high Venus surface temperature and pressure (470 °C, 90 atmospheres) returned by Venera 7, and measured the light level as suitable for surface photography, similar to an overcast day on Earth with roughly 1 km visibility.

Reader's Guide

Venera 8's significance lies in its confirmation and extension of the findings from Venera 7, providing the first detailed measurements of the Venusian surface environment. Its photometer measurements showed for the first time that the Venusian clouds end at a high altitude, and the atmosphere was relatively clear from there down to the surface. This clarified the structure of Venus's atmosphere and indicated that surface photography was feasible. The on-board gamma ray spectrometer measured the uranium/thorium/potassium ratio of the surface rock, indicating it was similar to alkali basalt, offering the first direct geochemical data from another planet's surface. The probe's 50-minute survival on the surface, despite extreme temperature and pressure, demonstrated improved engineering over its predecessor. Its data on illumination, wind speeds, and atmospheric composition helped shape subsequent Venus exploration strategies. The mission remains a key milestone in planetary science, providing foundational knowledge about Venus's surface conditions and geology.

Did You Know?

• Venera 8 was the second robotic space probe to conduct a successful landing on the surface of Venus.
• The lander transmitted data for 50 minutes, 11 seconds after landing before failing due to harsh surface conditions.
• Its photometer measurements showed for the first time that the Venusian clouds end at a high altitude.
• The gamma ray spectrometer measured the surface rock composition as similar to alkali basalt.