Planetary Exploration: Doubleheader on Venus

Right on target, more than four months after leaving the earth, two Russian spacecraft last week plunged into the murky atmosphere of Venus. Both Venus 5 and Venus 6 had apparently stood up well under the rigors of their 217-million-mile trips. Each spacecraft successfully ejected an instrumented capsule that radioed back information while parachuting toward the Venusian surface. At week's end, however, both capsules appeared to have fallen victim to intense Venusian heat before making their landings on the planet's surface.

When the 2,491-lb. Venus 5 was 31,000 miles from Venus, Soviet ground controllers sent a signal that separated the instrument capsule from the speeding craft. Protected by a heat shield while its descent was slowing, the capsule eventually deployed a parachute and began radioing information about the temperature, pressure and chemical composition of the atmosphere. After 53 minutes of transmission, the capsule's signals abruptly ceased. With no word from the Russians, Western scientists concluded that the intense heat of the lower atmosphere had disabled the transmitters before the capsule crashed. They recalled that in 1967 a similar Russian capsule—Venus 4—had fallen silent after 90 minutes of transmission, just as it was recording a temperature of 536° F.

Venus 5 was followed a day later by Venus 6, which ejected a capsule that transmitted for 51 minutes before it too died out. Only the Russians could tell how successful their two latest Venus shots had been and how much information had been gathered about the enigmatic planet. Whatever they learned, the Soviets undoubtedly left some mark on Venus. On board the Venus 5 capsule, Tass reported, was a marker bearing a bas-relief of Lenin and the Soviet coat of arms.