In August 1970 a Molniya rocket lifted off from Baikonur carrying Venera 7, a Soviet probe built to survive a descent to the surface of Venus. On 15 December 1970 its capsule landed and sent back roughly 23 minutes of faint signals, the first data ever transmitted from the surface of another planet. Its readings of about 475°C and a pressure some 90 times Earth's confirmed that Venus is an inferno beneath its clouds.
By 1970 the Soviet Union had already sent several Venera probes into the Venusian atmosphere, and each had been crushed or cooked before reaching the ground. Engineers at the Lavochkin design bureau responded by building Venera 7's descent capsule as a reinforced titanium shell, rated to withstand far higher pressures than its predecessors and cooled before entry so it could last longer in the heat. A twin spacecraft launched days later, designated Kosmos 359, never escaped Earth orbit, leaving Venera 7 to carry the mission alone on its four-month cruise.
On 15 December 1970 the capsule plunged into the thick atmosphere and deployed its parachute, which appears to have failed partway down. The lander struck the surface at roughly 17 meters per second, around 60 kilometers per hour, and may have come to rest tipped on its side. Its transmissions seemed to stop at impact, and controllers initially believed the mission had ended in the air.
Only when scientists reprocessed the recorded tapes did they find a signal buried in the noise, about one percent as strong as the transmissions during descent, persisting for roughly 23 minutes after landing. That whisper carried temperature data showing about 475°C at the surface, hot enough to melt lead, and supported estimates of a pressure near 90 atmospheres. Venera 7 had made the first soft landing on another planet to return data, and it set the stage for later Veneras that would photograph the Venusian ground.
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