Astronomy: Venus Revisited

Only a generation back, Venus was commonly thought of as a fine abode for lush, jungly life. As scientists learned more about the cloud-shrouded planet, its real estate values plummeted. Modern studies of Venus have pictured it as hot and waterless, certainly not a place for any kind of life that is known on earth. But last week Venus got a kind word. Professor John Strong of Johns Hopkins University reported that the Venusian atmosphere has a large amount of water vapor above its sunlit cloud deck.

Dr. Strong got his information from a giant balloon belonging to the Air Force Cambridge Research Laboratory that carried a telescope above nearly all of the earth's atmosphere. An automatic pointing device locked on the sun and used it as a reference point to focus the telescope on Venus. Then the telescope photographed the spectrum of solar infra-red light reflected from the top of the cloud deck.

Earlier attempts to look for water on Venus had been frustrated by the masking effect of the abundant water vapor in the earth's lower atmosphere, but the 87,500-ft. level where the balloon-telescope took its pictures is above nearly all of the earth's vapor. Thus the spectral absorption that it photographed was almost entirely free from earthside confusion. Says Dr. Strong: "About 95% of the water that we saw was on Venus."

Analysis of the spectra showed that above its cloud deck, the Venusian atmosphere has about 9.8 milligrams of water vapor per square centimeter. This is not much, but it is not far from the amount that is believed to exist above a comparable level in the earth's atmosphere.

Dr. Strong prefers not to decide whether the presence of water vapor means that the dense Venusian clouds are made of water droplets like the earth's clouds or whether they are dust or hydrocarbons, as some authorities think. "I have now come to the end of my competence," he says, "but my personal opinion is that it does imply water." Further deductions are even more iffy, but Dr. Strong suspects that free oxygen may exist along with carbon dioxide in the Venusian atmosphere. If so, it probably comes from water molecules that are broken into hydrogen and oxygen by ultraviolet radiation from the sun.

Where water exists at reasonable temperature, life may exist too, even if only as microscopic organisms floating in the clouds. Dr. Strong believes that "the proof of water vapor forces us to re-examine every previous calculation made concerning the possibility of some sort of life existing on Venus. The case is not closed yet."