Cosmic Connection

by Carl Sagan

  It is difficult to escape the conclusion–which, in a sense, is implicit in Darwinian natural selection–that all life on Earth has evolved from a single instance of the origin of life. If this is true, there is an important sense in which the biologist cannot distinguish the necessary from the contingent, that is, distinguish those aspects of life that any organism anywhere in the universe must have simply in order to be alive, from those aspects of life that are the results of the tortuous evolution by small opportunistic adaptations.

  The production of simple organic (carbon-based) molecules under simulated primitive planetary conditions is now subject to active laboratory investigation. As we saw earlier, the molecules of which we are made can be produced rather easily, in the absence of life, under quite general primitive planetary conditions. But it is not practicable to perform laboratory experiments on even the early stages of biological evolution: The time scales are too long. It is only by examining living systems elsewhere that biologists can determine what other possibilities there are.

  It is for this reason that the discovery of even an extremely simple organism on Mars would have profound biological significance. On the other hand, if Mars proves to be lifeless, a natural experiment has been performed for us: Two planets, in many respects similar; but on one life has evolved, on the other it has not. By comparing the experimental with the control planet, much may be discovered about the origin of life. Similarly, the search for prebiological organic chemicals on the Moon, on Mars, or on Jupiter is of great importance in understanding the steps leading to the origin of life.

  As another example of the perspective provided by planetary studies, consider meteorology. The problems of turbulent flow and fluid dynamics are among the most difficult in all of physics. Some insights into the Earth’s weather have been obtained by standing back and examining, by photography from meteorological satellites, the circulation of the Earth’s atmosphere. Still, meteorological theory for the Earth is today capable of long-range weather predictions, but only over very large geographical areas, for a range of simplifying assumptions, and for only a little time into the future. Laboratory studies of atmospheric circulation have a limited scope; classically, they are performed in modified dishpans.

  It would be nice to do a “Joshua” experiment, stopping the Earth from turning for a while. The change in circulation would provide insights into the role of the Earth’s rotation (particularly through Coriolis forces) in determining the circulation. But such an experiment is technologically very difficult. It also has undesirable side-effects. On the other hand, the planet Venus, with approximately the same mass and radius as Earth, has a rotation rate 240 times slower–so slow that Coriolis forces will be minor. The atmosphere is much thicker on Venus than on Earth. Nature has arranged a natural experiment for the meteorologists.

  Jupiter rotates about once every ten hours; here is an enormous planet that turns faster than Earth does. The effects of rotation should be much more important than on Earth, and, indeed, Jupiter gives the impression of having a seething, roiling, turbulent atmosphere; its prominent atmospheric bands and belts are almost certainly related to the rapid rotation. Nature has arranged two comparison experiments–two planets with massive atmospheres, one rotating slowly, the other rapidly. An understanding of the circulation of the massive atmospheres of Venus and Jupiter will improve our understanding of oceanic, as well as atmospheric, circulation on Earth.

  Or consider the planet Mars. Here is a planet with–quite remarkably–the same period of rotation and the same inclination of its axis of rotation to its orbital plane as Earth. But its atmosphere is only 1 percent of ours, and it has no oceans and no liquid water. Mars is a control experiment on the influence of oceans and liquid water on atmospheric circulation.

  Until recently, the geologist has been restricted to one object of study, the Earth. He was unable to decide which properties of the Earth are fundamental to all planetary surfaces and which are peculiar to the unique circumstances of Earth. For example, seismographic observations of earthquakes have revealed the interior structure of Earth and its division into crust, mantle, liquid metal core, and solid inner core. But the reason Earth is so divided remains largely obscure. Was Earth’s crust exuded from the mantle through geological time? Did it fall from the skies in an early catastrophic event? Has Earth’s core formed gradually through geological time by the sinking of iron through the mantle? Or did it form discontinuously, perhaps in a molten Earth at the time of the origin of our planet? Such questions can be examined by performing seismometric observations on the surfaces of other planets; they could be relatively inexpensive experiments performed automatically by existing instrumentation.

  There is now reasonably convincing evidence of continental drift. The motion of Africa and South America away from each other is the best-known example. In some theories, the driving force of continental drift and of the evolution of the interior of our planet are connected–for example, through convection currents circulating slowly between core and crust in the mantle. Such connections between surface geology and planetary interiors are just beginning to emerge in the study of other planets. We test our understanding of such connections by testing whether they apply elsewhere.

  The perspectives gained in studies like these have a range of practical consequences. A generalization of the science of meteorology may lead to great improvements in weather forecasting. It may even lead to weather modification. The study of the atmosphere of Venus has already led to the theory that a runaway “greenhouse” effect has occurred there–an unstable equilibrium in which an increase in temperature leads to an increase in the atmospheric water vapor content, leading through infrared absorption of thermal radiation from the planet to a yet further increase in surface temperature, and so on. Had Earth started out only slightly closer to the Sun than it did, preliminary theoretical estimates indicate that we might have ended up as a searing hot Venus. But we live in a time when the atmosphere of Earth is being strongly modified by the activities of Man. It is of the first importance to understand precisely what happened on Venus so that an accidental recapitulation on Earth of the runaway Venus greenhouse can be avoided.

  The studies of the surfaces and interiors of the planets may be of great practical benefit in earthquake prediction and in remote geological prospecting for minerals of value on Earth.

  The revolution in biology that the discovery of indigenous life elsewhere would surely bring may have a range of unsuspected practical benefits, particularly to the extent that research in cancer and aging is now limited by ideas rather than money.

  The study of the highly condensed matter in neutron stars and the enormous energy productions in the centers of galaxies and in quasars has already led to suggestions about possible modifications of the laws of physics, laws that have been deduced on Earth to explain phenomena observed on Earth.

  The exploration of space will inevitably provide a wealth of practical benefits. But the history of science suggests that the most important of these will be unexpected–benefits we are today not wise enough to anticipate.

  8. Space Exploration as a Human Enterprise

  II. The Public Interest

  Direct scientific interest in space exploration and the practical consequences that can be imagined flowing from them are not the principal or even the most general interests that space exploration holds for the layman. There is today–in a time when old beliefs are withering–a kind of philosophical hunger, a need to know who we are and how we got here. There is an ongoing search, often unconscious, for a cosmic perspective for humanity. This can be seen in innumerable ways, but most clearly on the college campus. There, an enormous interest is apparent in a range of pseudoscientific or borderline-scientific topics–astrology, Scientology, the study of unidentified flying objects, investigation of the works of Immanuel Velikovsky, and even science-fiction superheroes–all of which represent an attempt, overwhelmingly unsuccessful in my view, to provide a cosmic perspec
tive for mankind. Professor George Wald, of Harvard, is thinking of this longing for a cosmic perspective when he writes: “We have desperately to find our way back to human values. I would even say to religion. There is nothing supernatural, in my mind. Nature is my religion, and it’s enough for me… What I mean is: We need some widely shared view of the place of Man in the Universe.”

  The most widely sold book in college communities from Cambridge, Massachusetts, to Berkeley, California, in recent years was called The Whole Earth Catalog, which viewed itself as providing access to tools for the creation of cultural alternatives. What was striking was the number of works displayed in the Catalog that related to a scientific cosmic perspective. They ranged from the Hubble Atlas of Galaxies to flags and posters of Earth photography near full phase. The title of The Whole Earth Catalog derives from its founder’s urge to see a photograph of our planet as a whole. The Fall 1970 issue expanded this perspective, showing a photograph of the whole Milky Way Galaxy.

  There is a similar trend apparent in some modern art and in rock ‘n’ roll music: “Cosmo’s Factory” by Creedence Clearwater Revival, “Starship” by the Jefferson Airplane, “Mr. Spaceman” and “CTA 102” by the Byrds, “Mr. Rocket Man” by Elton John, and many others.

  Such interest is not restricted to the young. There is a tradition in the United States of public-subscription support of astronomy. Construction of entire observatories and salaries for staff have been paid for voluntarily by the local communities. Several million people visit planetariums in North America and Britain each year.

  The current resurgence of interest in the ecology of the planet Earth is also connected with this longing for a cosmic perspective. Many of the leaders of the ecological movement in the United States were originally stimulated to action by photographs of Earth taken from space, pictures revealing a tiny, delicate, and fragile world, exquisitely sensitive to the depredations of man–a meadow in the middle of the sky.

  As the results of space exploration and their accompanying new perspectives on Earth and its inhabitants permeate our society, they must, I believe, have consequences in literature and poetry, in the visual arts and music. The distinguished American physicist Richard Feynman writes: “It does no harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined! Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?”1

  1 Richard Feynman, Introduction to Physics, Vol. I, Addison Wesley, pp. 3-6.

  But mere general exploration does not yet motivate pervasive public interest in space. For many, the rocks returned from the Moon were a great disappointment. They were seen as merely rocks. What role they might play in chronicling the days of creation of the Earth-Moon system has not yet been explained adequately to the public.

  Where public interest in space is most apparent is in cosmology and in the search for extraterrestrial life, topics that strike resonant chords in a significant fraction of mankind. The fact that much more newspaper space is given to the most casual hypothesis on exobiology than to many of the most careful and important results in other areas is an accurate reflection of where public interest lies. The discovery of interstellar microwave lines of formaldehyde and hydrogen cyanide has been widely described in the public press as connected, through a long set of linkages, to questions in biology.

  While it is true that the average person thinks in terms of mild variants of human beings when he is asked to imagine extraterrestrial life, it is also true that interest even in Martian microbes is much larger than in many other areas of space exploration. The search for extraterrestrial life could be a keystone of public support for space experiments–experiments oriented both within and beyond the Solar System.

  There are many possible viewpoints on the present and near-future costs of space science and astronomy. Because the annual costs of ground-based astronomy are only a few percent of the costs of the scientific space program, I will concentrate on the price of the latter. It is customary to compare expenditures on space to annual expenditures in the United States for ethyl alcohol or bubble gum or cosmetics. I personally find it more useful to compare the costs with those of the U. S. Department of Defense. Using a report of the government’s General Accounting Office (the New York Times, July 19, 1970), we learn that the total anticipated cost of the Viking mission to land on Mars in 1976 is about half that of the cost overruns in the so-called Safeguard antiballistic missile system for fiscal year 1970. The cost of a Grand Tour exploration of all the planets in the outer Solar System (canceled for lack of funds) is comparable to the 1970 cost overruns on the Minuteman III system; the cost of a very large optical telescope in space, capable of definitive studies of the origins of the universe, is comparable to the 1970 cost overruns on the Minuteman II missile; and a major program of Earth resources satellites, involving several years of close inspection of the surface and weather of our planet, would cost approximately the fiscal year 1970 cost overruns on the P-3C aircraft. A decade-long program of systematic investigation of the entire Solar System would cost as much as the accounting mistakes on a single “defense” weapons system in a single year. The scientific space program is small change compared to the errors in the Department of Defense budget.

  Another viewpoint worth considering is space exploration as entertainment. A Viking Mars-lander could be completely funded through the sale, to every American, of a single issue of a magazine, containing pictures taken on the surface of Mars by Viking. Photographs of the Earth, the Moon, the planets, and spiral and irregular galaxies are an appropriate and even characteristic art form of our age. Such novel and oddly moving photographs as the Lunar Orbiter image of the interior of the crater Copernicus and the Mariner 9 photography of the Martian volcanoes, windstreaks, moons, and polar icecaps speak both to a sense of wonder and to a sense of art. An unmanned roving vehicle on Mars could probably be supported by subscription television. A phonograph record of the output of a microphone on Mars, where there seems to be a great deal of acoustic energy, might have wide sales.

  I do not wish here to broach the debate on manned vs. unmanned planetary exploration, except to stress again that there may be very good nonscientific reasons for sending men into space. There exist intermediate cases between manned and unmanned exploration, which we may very well see in the forthcoming decades. For example, there may be telepuppets, devices landed on another planet but fully controlled by an individual human being in orbit, all of whose senses are in a feedback loop with the device. It is also possible that planets with very hostile environments by terrestrial standards, or planets where there is a great danger of contamination by terrestrial micro-organisms, will be explored by men inside machines like enormous prosthetic devices, amplifying the sense perceptions and muscular abilities of the human operator.

  Even apart from these hypothetical developments, it is already quite clear that the development of sophisticated devices for unmanned planetary exploration is organizing the same technology required for the production of useful robots on the Earth. An unmanned vehicle that lands on Mars by the early 1980s will very likely have the ability to sense its environment much more thoroughly than humans are able to, to rove over the landscape, to make both preprogrammed decisions and decisions based on information newly acquired. First cousins to such a robot, some mass-produced, would be extremely useful devices here on Earth. I am thinking in part of operations in inaccessible environments such as the abyssal floor of the ocean basins, but I am also thinking of industrial robots to free workers from repetitive and uninteresting tasks, and domestic robots to liberate the housekeeper from a life of drudgery.

  The experience of space exploration gives no unique philosophy; to some extent, each group tends to see its own philosophical view reflected, and not always by the soundest logic: Nikita Khrushchev stressed that in the space flight of Yur
i Gagarin no angels or other supernatural beings were detected; and, in almost perfect counterpoint, the Apollo 8 astronauts read from lunar orbit the Babylonian cosmogony enshrined in Genesis, Chapter 1, as if to reassure their American audience that the exploration of the Moon was not really in contradiction to anyone’s religious beliefs. But it is striking how space exploration leads directly to religious and philosophical questions.

  I believe that military control of manned space flight–in practice in the Soviet Union and a subject of current debate in the United States–is a step that supporters of peace should back. The military establishments of the United States and the Soviet Union are, I am afraid, establishments with vested interests in war. They are meticulously trained for war; in time of war, there are rapid promotions, increases in pay, and opportunities for valor that are absent in peacetime. Where eager readiness for warfare exists, the likelihood of intentional or accidental warfare becomes much greater. By virtue of their training and temperament, military men are often not interested in other sorts of gainful employment. There are few other ways of life with the perquisites of power of the military officer. If peace broke out, the officer corps, their services no longer as necessary, would be profoundly discomfited. Premier Khrushchev once attempted to cashier a large number of senior officers in the Red Army, putting them in charge of hydroelectric power stations and the like. This was not to their liking, and in something like a year most of them were back in their old jobs. In fact, the military establishments in the United States and the Soviet Union owe their jobs to each other, and there is a very real sense in which they form a natural alliance against the rest of us.