New Venus Landing

After a 117-day journey across 180 million miles of space, the spherical Venera 8, emblazoned with a hammer and sickle and a portrait of Lenin, plummeted toward the thin, sunlit crescent of Venus that is now visible from earth. Under its heat-resistant parachute, the 2,600-lb. spacecraft floated down through the thick, hot Venusian atmosphere. After it landed, it continued sending signals for about 50 minutes before it burned out on the scalding Venusian surface.

Pravda promptly hailed the second successful landing in eight Russian Venus probes as "another victory of Soviet science and technology." American scientists, who have sent two spacecraft flying past Venus, were quick to agree. By broadcasting from the surface 37 minutes longer than Venera 7 in December 1970, the latest space shot showed that the Soviet engineers had 1) designed a cooling system that could temporarily withstand the enormous surface temperatures of Venus (more than 900DEG F.) and 2) built a spacecraft that would not buckle under the planet's crushing surface pressures (about 100 times those of the earth).

Molten Pools. Venera was also equipped with a gamma-ray detector that should provide the first on-site evidence as to the composition and structure of the Venusian "soil." That evidence is not likely to be very inviting. As late as the 1950s, many astronomers still thought that conditions on cloud-shrouded Venus might favor life, but by now they know otherwise. Rotating once every 243 days in a direction opposite to that of the other planets, Venus has a surface that University of Arizona Astronomer Gerard Kuiper says might resemble a fresh volcanic field, with boiling sulfur springs and red-hot pools of molten metals. The planet's atmosphere is no less forbidding--mostly carbon dioxide plus thick yellow clouds that may be a poisonous brew of such substances as hydrochloric acid, ammonium chloride or salts of mercury. In fact, the composition of these clouds is still a prime question for scientists. Only in the upper layers does the atmosphere even vaguely resemble that of the earth, leading Astronomer Carl Sagan to speculate that these upper layers might harbor primitive Ping-Pong-ball-sized floating organisms.

Because it is the second planet from the sun, Venus is exposed to about twice as much solar radiation as the earth. But this proximity alone does not account for the high Venusian temperature. While its carbon-dioxide atmosphere lets in the sun's radiation, it also keeps in the heat (infrared rays) given off from the planet's surface, thus creating a "greenhouse effect." Furthermore, as the temperature rises, more carbon dioxide is boiled into the atmosphere, only to increase the effect.

Some scientists fear that a similar greenhouse effect may some day afflict the earth, as carbon dioxide and other gases accumulate in the atmosphere from the burning of fossil fuels--or simply from the evolution of the sun. In Science recently, Sagan and Physicist George Mullen predicted that the greenhouse effect will ultimately be caused by the sun getting hotter and evaporating more water into the atmosphere. Indeed, their calculations show that in 3 billion to 4.5 billion years, the earth's atmosphere will become so thick and steamy with water vapor that it will resemble that of Venus. At the same time, Sagan and Mullen say, the thin atmosphere of Mars will also be heated and thickened until it resembles that of the present-day earth. With dry scientific understatement, they add: "If there are any organisms left on our planet in that remote epoch, they may wish to take advantage of this coincidence."

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