Planetary Exploration: Vital Statistics from Venus

When Russia's Venus 4 capsule suddenly fell silent in the thick Venusian atmosphere last October, Soviet scientists assumed that the spacecraft's final readings—a temperature of 520° F. and an atmospheric pressure 15 to 22 times greater than Earth's—described conditions on the planet's surface. Not so, say U.S. Electrical Engineers Arvydas Kliore and Dan Cain. The Venusian at mosphere, they report in the current issue of Journal of Atmospheric Sciences, is much hotter and far more crushing than the Soviets think. On the surface the temperature is actually close to 900° F., the atmospheric pressure a staggering 75 to 100 times the sea level pressure on Earth.

Their own figures, the two Jet Propulsion Laboratory scientists explain, are based not only on data from Venus 4 but also on transmissions from the U.S. spacecraft Mariner 5 which flew past Venus less than two days after the Russian landing. According to JPL, the Russian capsule stopped sending signals when it was 3,774 miles from the center of Venus. But recent measurements by four powerful U.S. radar installations have established that the planet's radius is only 3,759 miles. That means that at the instant Venus 4 stopped transmitting, it must have been 15 miles above the planet's surface. The capsule, Kliore and Cain speculate, may have landed on a Venusian mountain three times as high as Mount Everest. Or more likely, it may have gone dead while still floating down through the atmosphere—a victim of electronic heat prostration. To back up their temperature estimate, the JPL men also point out that U.S. radio astronomy measurements and data from Mariner 2, which bypassed Venus in 1962, indicate a Venusian surface temperature of at least 800° F.

The new findings make it less likely than ever that future space probes will find any kind of life on Venus. A surface compression of 75 atmospheres is as crushing as the pressure of water 2,550 ft. below the ocean's surface. A temperature of 900° F. is more than enough to melt lead or zinc, or do in any form of life familiar to Earthmen.