Cosmic Connection (12 page)

At the 1968 Tokyo meeting of COSPAR, the Committee on Space Research of the International Council of Scientific Unions, I proposed that the
Venera 4
spacecraft had ceased operating some fifteen miles above the surface. My colleague, Professor A. D. Kuzmin, of the Lebedev Physical Institute, in Moscow, argued that it had landed on the surface. When I noted that the radio and radar data did not put the surface at the altitude deduced for the
Venera 4
touchdown, Dr. Kuzmin proposed that
Venera 4
had landed atop a high mountain. I argued that ground-based radar studies of Venus had shown mountains a mile high, at most, and that it was exceptionally unlikely
Venera 4
would land on the only fifteen-mile-high mountain on Venus, even if such a mountain were possible. Professor Kuzmin replied by asking me what I thought was the probability that the first German bomb to fall on Leningrad in World War II would kill the only elephant in the Leningrad zoo. I admitted that the chance was very small, indeed. He responded, triumphantly, with the information that such was indeed the fate of the Leningrad elephant.

The designers of subsequent Soviet entry probes were, despite the Leningrad zoo, cautious enough to increase the structural strength of the spacecraft in each successive mission.
Venera 7
was able to withstand pressures of 180 times that at the surface of the Earth, a quite adequate margin for the actual Venus surface conditions. It transmitted twenty minutes’ worth of data from the Venus surface before being fried.
Venera
8, in 1972, transmitted more than twice as long. The surface pressure is not at twenty atmospheres, and the spectacular Mount Kuzmin does not exist.

The principal conclusion about the scientific method that I draw from this history is this: While theory is useful in the design of experiments, only direct experiments will convince everyone. Based only on my indirect conclusions, there would today still be many people who did not believe in a hot Venus. As a result of the
Venera
observations, everyone acknowledges a Venus of crushing pressures, stifling heat, dim illumination, and strange optical effects.

That our sister planet should be so different from Earth is a major scientific problem, and studies of Venus are of the greatest interest in understanding the earliest history of Earth. In addition, it helps to calibrate the reliability of astral projection and spirit travel of the sorts popularized by Emanuel Swedenborg, Annie Besant, and innumerable present-day imitators, none of whom caught a glimmering of the true nature of Venus.

T
he planet Venus floats, serene and lovely, in the sky of Earth, a bright pinpoint of yellowish-white light. Seen or photographed through a telescope, a featureless disc is discerned; a vast unbroken and enigmatic cloud layer shields the surface from our view. No human eye has seen the ground of our nearest planetary neighbor.

But we now know a great deal about Venus. From radio telescope and spacevehicle observations, we know that the surface temperature is about 900 degrees Fahrenheit. The atmospheric pressure at the surface of Venus is about ninety times that which we experience at the surface of the Earth. Since the planet’s gravity is about as strong as the Earth’s, there are about ninety times more molecules in the atmosphere of Venus as in the atmosphere of Earth. This dense atmosphere acts as a kind of insulating blanket, keeping the surface hot through the greenhouse effect and smoothing out temperature differences from place to place. The pole of Venus is probably not significantly colder than its equator, and on Venus it is as hot at midnight as at noon.

Forty miles above the surface is the thick cloud layer that we see from Earth. At least until recently, no one knew the composition of these clouds. I had proposed that they were constituted in part of water, a cosmically very abundant material, which could account for many but by no means all of the observed properties of the Venus clouds. But there were many other candidate materials proposed, among them, ammonium chloride, carbon suboxide, various silicates and oxides, solutions of hydrochloric acid, a hydrated ferric chloride, carbohydrates, and hydrocarbons. These last two materials were proposed by Immanuel Velikovsky in his speculative romance
Worlds in Collision
to provide manna for the Israelites during their forty years of wandering in the desert. The other candidate materials were proposed on somewhat firmer grounds. Yet each of them ran afoul of one or more of the observations.

But recently a material has been proposed that is in excellent quantitative agreement with all of the measurements. The American astronomer Andrew T. Young has shown that the clouds of Venus are very likely a concentrated solution of sulfuric acid. A 75 percent solution of H
₂
SO
₄
precisely matches the index of refraction of the Venus clouds determined by polarimetric observations from the Earth. None of the other materials comes close. Such a solution is liquid at the temperatures and pressures at which the Venus clouds reside. Sulfuric acid has an absorption feature, determined by infrared spectroscopy, at a wavelength of 11.2 microns. Of all the materials proposed, only H
₂
SO
₄
has such an absorption feature. The Soviet entry spacecraft of the
Venera
series have found large quantities of water vapor below the visible clouds of Venus. Ground-based observers looking for water vapor spectroscopically have found only a tiny amount of water vapor above the clouds of Venus. The two observations are in accord only if a very effective drying agent is present between these two regions. Sulfuric acid is such an agent.

In the Earth’s atmosphere there are water droplets at altitude, and water vapor in the atmosphere below. Likewise on Venus: If there are sulfuric acid droplets in the high clouds, there must be gaseous sulfuric acid below, with a relatively high concentration near the surface. Astronomers in Earth-bound observatories have also found unmistakable evidence of hydrochloric acid and hydrofluoric acid as gases in the upper atmosphere of Venus. They also must exist in a fair concentration–for example, the relative proportions of Los Angeles smog in Los Angeles air–in the lower atmosphere of Venus. These three acids are an extremely corrosive mixture. Any spacecraft that is to survive on the Venus surface must not only be bulwarked against the high pressures but protected against the corrosive atmosphere.

The Soviet Union is engaged in a very active program of unmanned exploration of Venus. We now know there is enough light for photography at midday on the Venus surface. The time will come, in not too many years, I think, when we will have our first photographs of the surface of Venus. What does the surface of Venus look like? To some extent we can already make predictions.

Because of the very dense atmosphere of Venus, there are some interesting optical effects. The most important such effect is due to Rayleigh scattering, named after the British Lord Rayleigh. When sunlight strikes the clear, dust-free atmosphere of the Earth, it is scattered. Photons strike the molecules of the Earth’s atmosphere and are bounced off. Many such bounces may occur. But because the molecules of air are very much smaller than the wavelength of light, it turns out that short wavelengths are scattered or bounced away by the air molecules more efficiently than long wavelengths. Blue light is scattered much better than red light. This was a fact known to Leonardo da Vinci, who painted distant landscapes in an exquisite cerulean blue. It is why we talk of purple mountains; it is why the sky is blue. The light from the sun is scattered about in our atmosphere–some of it being scattered up and out again, but other fractions of sunlight being scattered about by the molecules of our atmosphere and then, from quite a different direction than that of the Sun, scattered back down to our eyeballs. In the absence of an atmosphere, as on the Moon, the sky is black. When we look at a sunset we are seeing the Sun through a longer path in the Earth’s atmosphere than when we view it at noon. Blue light has been preferentially scattered out of this path, leaving only the red light to strike our eyes. The beauty of the sunset, the sky, and distant landscapes are all due to Rayleigh scattering.

What about Rayleigh scattering on Venus? Because the atmosphere is so much denser, Rayleigh scattering there is much more important. Were we to strip the clouds off Venus, we would still be unable to see its surface from above. Visible light of all colors would be scattered so many times in the Venus atmosphere that no image of any surface details would be discerned. In the near infrared, at wavelengths longer than the human eye is sensitive to, the surface could, however, be seen from above. But there are clouds. Radio waves penetrate the clouds and the atmosphere of Venus and the first radar maps of Venus are being developed (see page 80). In a few years, Cornell University’s great Arecibo telescope in Puerto Rico will begin mapping the surface of Venus by radar with higher precision than the best ground-based optical maps of the Moon. Already, there are hints of mountain ranges and great impact basins on the surface of this enigmatic planet.

At the surface of Venus, Rayleigh scattering is also an extremely important effect. Just as we cannot see the surface in visible light from above Venus, we cannot see the sun in visible light from the surface of Venus–even if there were a break in the clouds. If there were intelligent life on Venus, astronomy would be very slow to develop; and radio astronomy would emerge first. The
Venera 8
spacecraft found that sunlight does reach the surface of Venus during the day, but it is so attenuated by passage through the clouds and atmosphere that, even at midday, it is no brighter on Venus than at twilight on the Earth. The sunlight would be a hazy and diffuse patch of deep ruby-red light, whose rising and setting could only indistinctly be determined.

If you were standing in some protective suit on the surface of Venus and put on violet sunglasses, you would see no farther than a few dozen feet. The Rayleigh scattering in blue light is so strong on Venus that the visibility in the violet is small. But because long wavelength light is scattered less than blue, at the extreme red end of the visible spectrum–with red sunglasses on–you could see perhaps a thousand feet. At the surface of Venus everything would be suffused in a deep red gloom. We would have a perception of color, but only for objects very close to us. Our surroundings would be an indistinct roseate blur.

Venus thus seems to be a place quite different from the Earth, and alarmingly unappealing: Broiling temperatures, crushing pressures, noxious and corrosive gases, sulfurous smells, and a landscape immersed in a ruddy gloom.

Curiously enough, there is a place astonishingly like this in the superstition, folklore and legends of men. We call it Hell. In the older belief–that of the Greeks, for example–it was the place where all human souls journeyed after death. In Christian times it has been thought of as the post-mortem destination only of one of two categories of moral persuasion. But there is little doubt that the average person’s view of Hell–sizzling, choking, sulfurous, and red–is a dead ringer for the surface of Venus.

Although terrestrial biological molecules would fall to pieces rapidly on Venus, there are organic molecules–for example, some with a complex ring structure–that would be quite stable under the conditions of Venus. It is difficult to exclude life there, but we can certainly say it would be quite different from what we are familiar with. Any organism that lives there would be wise to have leathery skin. Because of the high atmospheric pressures, it would even make sense to have little stubby wings, which could carry their possessors about without exceptionally strenuous flapping. A devil is a very good model–except for his mannish and goaty aspects–for an inhabitant of Venus. Milton and Isaiah called Lucifer “Son of the Morning,” the morning star. For thousands of years Venus and Hell have been identified.

This is all a very curious coincidence, but I cannot bring myself to think that it is anything more than that. The chief point is that in all the legends one gets to Hell by going down, not up. The classical world of Greece and Rome and the ancient Near East were peppered with active volcanoes. Such volcanic terrains, like in contemporary Iceland and Hawaii, are bleak, desolate, and eerily beautiful landscapes. Sulfurous gases emanate from volcanic vents; lava fountains and flows suffuse the surroundings in red. It is very hot: You singe your eyebrows if you get too close to the lava in a collapsed lava tube. And all this heat, redness, and smell come from down below. It was not very difficult for our ancestors to imagine that volcanic terrains were apertures to a quite different igneous world called Hell.

The inside of the Earth and the outside of Venus are alike but not identical. They are both unpleasant for humans. But they are both of extreme scientific interest–worth at least an extended visitation, if not a homesteading. Dante knew about that.