Our Gamble in Space: The Search for Life

THE ATLANTIC

BY N. J. BERRILL

IN THIS age of space and atoms, hitching our wagon to a star seems to be the goal of man. Certainly in this first, fine, careless but expensive rapture, the accomplishments and prospects are exciting. The motives, however, are many and are generally mixed or confused. Although military performances already in the news, such as the recent attempts to place a belt of copper needles in the ionosphere and the calamitous high-level explosions of Operation Rainbow, seem like blundering footsteps of blinded giants intent on carrying out a suicide pact, the momentum of military expediency has borne aloft the satellites and rockets that are set off into outer space for peaceful explorative purposes. The question is, what are we really trying to do?

The idea of venturing to planets of other solar systems is not now being seriously considered. This solar system has a magnitude and interest that are challenging enough without any thought of more distant, greener fields. Our own neighborhood comes first for many reasons. Even so, the real excitement tends to be overlooked in the publicity given to space exploration as such, just as in Antarctica the race to the Pole during the International Geophysical Year at first dominated the news, whereas in the coming Year of the Quiet Sun the increasingly cooperative international scientific investigation of that mysterious continent is unlikely to make headlines. A reporter can dwell more readily on the human aspects of a man in space than he can explain, for instance, the purpose and method of an orbiting geophysical laboratory.

Human nature is blessed, or perhaps cursed, with an inquiring mind and an itch for adventure, two qualities that may well spring from the same fount, although the mind can outstrip the body anytime. This is something we should be clear about in relation to exploring space. Dr. Philip Abelson, the new editor of Science, states that the billions of dollars now being spent on the moon race will not advance scientific knowledge as rapidly as knowledge might be advanced without sending a man to the moon, although he has no doubt that the manned lunar program will be carried to a successful conclusion in spite of the wasted time and cost. He says, “But let’s be clear. This isn’t science. It’s adventure and propaganda.” It is fun, to be sure, like any other spectator sport — although, fortunately, not at all imminent, since putting a man on either the moon or Mars in our present state of ignorance could spoil what may well be the most significant investigation mankind can make. For we are primarily searching for evidence of life beyond the limits of the earth, and it is vitally important not to contaminate other planets with any of the microbes that live so happily within us.

The development of military rocketry set the stage for the use of rockets and satellites for other purposes, which have concerned physicists, chemists, and engineers. The hardware had to come first. This has been put to use as a direct extension of projects and points of view developed or established as integral parts of the International Geophysical Year, primarily by physical scientists intent on furthering our knowledge of the earth as a particular kind of planet lying within the outermost zone of the sun’s atmosphere. The biologist has had to wait on the engineers and physicists for the application of space science to anything so delicate and complex as living organisms.

The National Aeronautics and Space Administration is aware of this, and the director of the Office of Space Sciences of NASA states flatly that the principal object of the space-science program is to extend human knowledge, and that it is fundamentally a basic research effort; obtaining environmental data on the atmosphere and space for other scientific uses, including support for practical applications, is a secondary objective.

Thus, the space-science program is at present concerned with geophysics, astronomy and solar physics, lunar and planetary investigations, interplanetary investigations, and, last, the biosciences. Briefly, in the area of geophysics, sounding rockets are used for the exploration of the atmosphere, for the testing of instrumentation, and for initial tryouts of experiments; in astronomy and solar physics the mainstay is the observatory type of satellite; obtaining samples from the moon’s surface is high on the priority list but late in the schedule because of the cost and difficulty involved; investigation of interplanetary space is regarded as an important area of research in itself; finally, in biosciences, NASA is still in the process of developing a program which will include the instrumentation of planetary probes for the search for extraterrestrial life, and also the development of a small recoverable satellite for conducting bioscience space experiments and the like. Roughly 15 percent of the total funds to be received by NASA are assigned to the spacescience program.

FOR biologists especially, the search for extraterrestrial life far outweighs the other two aspects of space biology, which are the admittedly immense task of putting man into space, adequately protected from hazards and sustained by a good simulation of his natural earthly environment; and the exploitation of the space environment for experiments on organisms under conditions hardly possible here on earth. No matter how great the effort and cost, there is no certainty that the search for life will be or can be successful. Yet the intellectual appeal is so overwhelming that nothing should stand in the way. The scientific question at stake is the most exciting, challenging, and profound issue of the whole naturalistic movement characteristic of Western thought for three hundred years, ranking with the revolutionary impacts of Darwin and Copernicus. According to Dr. Reynolds of the Office of Space Sciences, what is at stake is the chance to gain a wholly new perspective on man’s place in the universe, a truly new level of discussion on the meaning and nature of life.

The Darwinian revolution in biology contained the implicit conclusion that life itself was a part of the natural history of the planet as a whole. In the twentieth century the Russian biochemist Oparin made this explicit in his theory of the origination of life as a fully natural and virtually inevitable stage in the development of the earth, resulting from the sequence of chemical changes in the early history of this planet. This leads us directly to the question of the uniqueness of man and the life around him, and so toward the significance of man in the universe. Are we solitary freaks on a small planet of a middle-sized star in one of several billion galaxies and without significance in the scheme of things, or is life commonplace, as we now believe planetary systems to be? If any one of the other planets of our own solar system possesses any form of life that cannot be regarded as some stray from the earth, Oparin’s theory receives substantial support, and we can assume that where planets are, there life will also be. The fact of the existence of even the simplest form of life on another planet would overshadow in importance anything concerning its particular character. Martian microbes would suffice to prove the point, without need to find intelligent canal diggers or beings with prowess enough to have put the two small satellite moons of Mars into orbit, a suggestion that has been made.

Life as we know it is based on carbon and can exist in an active state only when incorporated in liquid water. The elements as a whole appear to be the same throughout the universe, and nothing that we know of them suggests that any other basis for life is possible. Within the solar system the search for life is reasonably restricted to those planets lying in the zone around the sun within which temperatures permit water to exist in liquid form. The orbit of the earth lies near the middle of this zone, and until recently the moon, Mars, and Venus were all considered to be within it, with Venus and Mars close to the inner and outer limits respectively. The moon has long been known to be without atmosphere or water and to be essentially dead. Mars is small compared with the earth but shows seasonal changes suggestive of some kind of life. Venus, virtually as large as the earth but covered with a dense cloud, has been a favorite prospect, with speculative proposals ranging from the presence of Coal Age types of forests and swamps to a surface entirely covered by oceans or oil fields, although spectroscopic evidence of an atmosphere heavily charged with carbon dioxide and seemingly devoid of oxygen and water vapor has been discouraging and more indicative of a dry and dusty planet.

Now, the Venus probe, Mariner II, has been highly successful both in its close passage to the planet and in its communication with the earth. Venus appears to be out-of-bounds, with a surface temperature above the melting point of lead and with no possibility of seas, however hot; with no magnetic field protecting its surface from solar and cosmic rays; and apparently with one face turned always toward the sun, like Mercury.

These facts are of great interest in our understanding the nature of the earth as a planet, for comparisons are essential, but they most definitely put Venus out of court as an abode of life of any sort that we can conceive. Mariner II confirms what had already been determined, somewhat less certainly, with earth-stationed instruments, particularly with radar systems.

From the facilities of the NASA deep-space tracking system at Goldstone, California, more than two hundred hours of radar contact and recorded data had been obtained, indicating a probable rotation period of once per orbit about the sun, as is the case with the moon’s about the earth. Radar signals beamed through Venus’ dense cloud cover, from laboratories in both the California Institute of Technology and the Massachusetts Institute of Technology, showed that the surface of Venus has no hills or valleys, or any irregularities of more than a few feet, and has the density of rock rather than of water or of any other liquid. Venus is, in fact, a much better radar reflector than the moon. All this is confirmed by Mariner II, and so successfully that a planned second Venus probe of the same type has been abandoned and attention is being directed to Mars.

MARS now offers the only real hope left for finding any kind of extraterrestrial life within the solar system, and it becomes vitally important that we do not fumble this remaining chance. The possibility that Mars may prove barren is no reason for holding back, nor can circumstantial negative evidence be accepted as final.

Three steps toward detection and analysis of Martian organisms, should they exist, are in progress or being planned. The first is to make more precise photographic and spectrographic analysis of Mars by means of telescopes directed toward the planet from high-altitude balloons and from orbiting satellites, thereby obviating the confusion and disturbance caused by the earth’s own atmosphere. This is of particular importance for understanding the nature of seasonal color changes, and also for detection of water vapor. Earlier observations show no sign of either water vapor or oxygen, although the fluctuating white polar caps of Mars are considered to be ice or frost rather than solid carbon dioxide. The seasonal green and orange colors of the lower latitudes in the Martian southern hemisphere, of even greater interest, may also be better examined from high-altitude or orbiting observatories.

The first stratosphere shot, made early in 1963, has been successful. The 36-inch Stratoscope II telescope of Princeton University has been sent aloft by balloon to a height of nearly fifteen miles by University of California scientists, from the site of the U.S. Scientific Balloon Flight Station in Texas. Water vapor and carbon dioxide have both been reported. Their presence is no proof of the existence of living organisms, but at least these facts are encouraging. Apparent lack of oxygen and the prevailing low temperatures suggest that any life on Mars is of a very low order, but even marginal forms of life can give us scientifically valuable information, particularly in the new branch of biological science known as molecular biology.

If, however, there is on Mars life which is responsible for the markings seen through terrestrial telescopes, then the suspected organisms must either be individually visible or must form colonies which cover the ground extensively. As such, they must also account for the color and the color changes, in response to changes in temperature and atmospheric moisture, and they must also account for the changes in size and shape of the dark and light areas and must be able to emerge again after being covered with yellow dust. No earthly organisms, such as lichens, for instance, could grow fast enough to account for these changes, although the general indication suggests something much more comparable to plant life than to animal life. Organisms comparable in any way to complex plants and showing extensive seasonal fluctuation would probably depend upon the coexistence of other organisms, comparable to decay bacteria, for recycling dead substance into renewed life. For our primary purpose, the discovery and analysis of microbial life would give us the answers we most desire. If Mars can be shown to possess any sort of indigenous life at all, we may feel assured that living organisms originate wherever circumstances permit, as a natural and inevitable evolution of universal matter.

The requisite circumstances are those of a planet large enough to produce and hold outer envelopes of gas and water, and so placed relative to its sun that water as such can exist. Mars is a small planet, apparently just large enough to retain adequate outer envelopes, and is also close to the lower temperature limits for the existence of liquid water. In these circumstances we should expect little more than life of a marginal kind. The discovery of only lowly forms of living organisms on Mars is to be expected, and this would support the general concept; although a failure to find life would merely indicate that Mars either lies a little beyond the pale or is too small to have produced or retained sufficient water at its surface, which would be disappointing but would in no way disprove the theory. On the other hand, a discovery that astronomer Lowell’s canals are real and that intelligent canal diggers have made them would be not only surprising and tremendously exciting but would be scientifically most disconcerting. According to theory, whatever Mars can do, earth should do better. However, although little is expected of Mars, that little may prove a lot.

THE study of life on earth has reached a critical stage in molecular biology. Bit by bit, living substance and living processes are being taken apart and reconstructed in the laboratory. The ways in which the commoner, lighter elements of the world around us, particularly hydrogen, carbon, nitrogen, oxygen, and sulfur, combine to form living matter, with phosphorus serving to energize it, are becoming more and more deeply understood. In the last two years, for instance, a Nobel Prize has been awarded to Melvin Calvin for tracing the paths by which the carbon of carbon dioxide becomes living substance during photosynthesis, and to James Watson and Francis Crick for cracking the so-called genetic code. This code can be likened to a four-letter alphabet making threeletter words responsible for directing the manufacture of the twenty amino acids, in various combinations and numbers, from which the essential living proteins of all organisms are made. The molecular basis of life is complex, almost infinitely variable, wonderfully organized, yet in certain respects beautifully simple.

The question is, how different could it all be and still add up to life? The answer can come in only two ways: by re-creating life in the laboratory but ringing the changes, a most ambitious project, or else by finding life on another planet and analyzing it for comparison with earthly life. Shall we find on Mars some of the unexplained peculiarities of terrestrial biology? With water apparently present but scarce, will Martian organisms consist of more than 90 percent water, which is the case for earthly organisms, except for their skeletons? Will the energy transfer system be based on phosphorus, as it is in organisms here, from bacteria to humans? If amino acids are the building blocks of living matter on Mars, will they all have a left-handed twist as they do on earth, or will right-handed forms be present instead, or as well, and with what consequences? Will organisms consist of cells with the same sort of chromosomal genetic mechanisms and apparatus for cell division? Will they have similar replication and information systems, as in the newly discovered genetic code? Will sex be necessary to ensure sufficient variability for evolution, and if so, will there be two sexes, as is customary here, or several, as in certain kinds of fungi? How much evolution has occurred, and how are Martian organisms adapted to their thin atmosphere, low oxygen, and the Martian range of temperature and seasons? And what evidence of the living past is recorded in the Martian rocks?

The answers to any and all of these questions would give us perspective with regard to our own evolution and the life around us. We would know better to what extent earthlings, including ourselves, are unique. In what degree are all planetary organisms basically alike, molded as they are from the common clay of inner planets? With this much understanding we, as human beings, could speculate with more assurance concerning the evolution of life and intelligence on other well-placed planets throughout the universe. Without it we could, of course, still speculate, but always with the haunting thought that we may be alone and insignificant. The missions to Mars will therefore be delicate and fraught with hope, however violent the blasts that send them off.

The first step is to send unmanned probes to Mars somewhat like that sent to Venus. The Russians launched such a probe late in 1962, which has already made its closest rendezvous, although so far there have been no reports. The United States plans to send a most elaborate instrument probe named Gulliver not later than 1966 and possibly much sooner now that Venus has already been examined so well and found wanting. Probes of the Gulliver type may well be our main concern throughout this decade.

Eventually, however, the search for life on Mars will almost certainly require that Martian samples be studied in manned laboratories, preferably here on earth. Many space scientists believe that the retrieval of Martian samples should be the ultimate purpose of exobiological projects and that it is unlikely that such retrieval can be accomplished by an unmanned expedition. Such a project is far more difficult than landing a man on the moon. Meanwhile, the unmanned missions will necessarily become fantastically sophisticated. Gulliver, as planned, is already so.

Whether or not Mars is inhabited by advanced forms of life, the objective of the Gulliver probes is to detect the presence of life at the microbial level. Gulliver is primarily a life seeker, no more and no less. The requirements, however, are rigorous. The instrumentation must be light in weight, small, rugged, able to withstand low temperature, low pressure, and vibration; it must survive eight or nine months of space flight and must complete the experiment rapidly; it must be sensitive to a small number of microorganisms and to as many kinds as possible; it must be able to transmit information back to the earth by telemetry; and it must withstand heat sterilization. Gulliver is designed to meet these needs. The missile itself has to land a miniature laboratory on the surface of Mars by parachute. The landed apparatus will then shoot out two projectiles, each containing twenty-three feet of sample-collection line, across the Martian earth. The two lines, impregnated with silicone grease for adhesion to Martian particles, will be wound back into a culture chamber, which will be sealed. Captured microorganisms multiply in a special broth containing radioactive substances and will liberate radioactive end products, particularly radioactive carbon dioxide, which can be detected by the instruments and reported back to earth.

During an international conference sponsored by UNESCO in which Gulliver was discussed, the Russian delegate asked if the proposed experiment does not assume that Martian bacteria would have the same taste in broth as terrestrial bacteria. The Americans conceded this, and efforts are now being made to devise experiments which would reveal the presence of exotic forms of microbes as well. The problem is to imagine forms with which we are totally unfamiliar and then to devise experiments to detect their presence. This is an extremely stimulating imaginative exercise to which a number of biologists are now applying themselves.

With so much at stake it becomes overwhelmingly important to safeguard Mars from invasion by terrestrial microbes which could seriously contaminate the planet or be picked up by the instruments and confuse the whole issue, perhaps permanently. Sterilization of the space vehicles and all that they contain is essential, but is no easy matter. They can be sterilized only if attention is given to sterilization requirements at all stages of design and construction. This, of course, is well recognized, and even the original Russian moon shot was presterilized. If we should find microbes on Mars or elsewhere, and if they should be remarkably like our own, we have to be certain that we ourselves did not plant them there. The precaution must be taken even though earthly organisms probably would have short shrift if they landed in such a strange environment already inhabited by native forms of life. By the same token, any space vehicles returning to earth after a planetary landing, a more remote prospect, may carry microbes or spores of dangerous character. Probably they would find the terrestrial environment too hostile, but if by chance this was a heaven awaiting them, they might convert all earthly life into a broth of a Martian type. This chance also is unlikely, but it cannot be ignored.

THE greater problem will arise when we have done all we can with unmanned space instruments and are ready to send manned expeditions. The difficulties in sending a man to Mars and back, far greater than the man-on-the-moon project, are such that it may not happen during the present century, which may be all to the good. Sterilizing a space vehicle and its instruments may not be easy, but sterilizing a human being is impossible. Each one of us harbors a community of diverse microorganisms that not only live happily within us and on us but are in some cases essential to our health. No matter how we purify our exterior, we carry a rich flora and fauna internally. Sending a man to Mars, if he is to become in any way exposed, is as big a threat to the life of that planet as we can make, and having him return home as a carrier of exotic microbes would be just as dangerous to us. The devastating impact of the white man’s germs on Pacific islanders and Eskimos during the nineteenth century should not be forgotten.

The question of spores in space is not new. Neither the cold nor the vacuum necessarily kills them, although cosmic radiation may be lethal. A theory of the origin of life, popular some decades ago, was that spores of living matter, which are known to be so small and light as to be driven by the pressure of light itself, long ago drifted onto the earth and started the proceedings here. The suggestion was intellectually unsatisfying since it shelved the final question of the origination of life by pushing it farther away in space and time. The fact remains, however, that spores of terrestrial microorganisms of various kinds drift to high levels in the earth’s atmosphere and probably drift off into space, impelled away by the pressure of light. Certain reddish bacteria actually live high in the atmosphere, by what means we do not know, and their spores may well be transmitted to space. A certain amount of living refuse, in other words, continually leaves the earth and is driven outward from the sun. Such spores may reach the moon and Mars, while the earth might receive spores from Venus, were there any to receive — a one-way gift, in any case, from the sun outward. If by this means we have already contaminated Mars, a continuing event that must have first begun during the early days of earthly life, we will find a confusing situation, since so much time has elapsed for Martian life, from any source, to have become peculiarly Martian. The moon, however, may serve as a guide.

The moon is an extremely small planet but conveniently close by. Its surface is naked to the outer night and to the glare of the sun and is devoid of air and water, although the physical texture of its surface is still a matter for conjecture. Whether the lunar craters have been produced by giant meteorites or by lunar volcanoes of the past, there is no doubt that small meteorites and cosmic dust have fallen onto the surface from time immemorial. The surface layer itself is now known to be transparent to radio waves to a depth of several yards from the visible surface, so that the moon may be covered with a filmy or foamy layer of light porous substance. Such a layer might well shield from continuing exposure to lethal light any spores picked up from the earth and perhaps elsewhere during the long past, and some spores may have escaped death from radiation. Moon sampling, for practical reasons, may be made long before effective samples can be obtained from Mars and may well be rewarding, for the moon may be a veritable museum of traces of life, preserved unchanged but essentially alive through an interminable past. The recent recovery of bacteria embedded in European rocksalt deposits of 180 million years ago and their growth into living colonies, supposing the bacteria are not more recent intruders into the salt, support this anticipation.

Once we enter the deepfreeze beyond the orbit of Mars, where lie the frozen but far from inactive outer planets of the solar system, no life can be expected, although further knowledge of these giant planets will greatly aid our understanding of the history and present nature of the solar system as a whole, as well as our understanding of the primeval nature of the earth and its atmospheres when earthly life was coming into being. If life exists elsewhere as highly evolved as it is here on earth, we will have to look for it far beyond the limits of the solar system; to other stars, like the sun, which are likely to be accompanied by planetary satellites. To assume that we are the one intelligent civilization in the universe would be presumptuous, yet there is little reason to believe we will ever travel beyond our own planetary neighborhood, the distances are so great. The distance even to the nearest stars is hard to visualize. For instance, if the earth is pictured as a barely visible grain of sand orbiting around a pea-sized sun less than three feet away, the nearest star, Proximar Centauri, is another pea 140 miles away, and the closest stars that might have habitable planets would be more than 600 miles distant. On the same scale it is only one foot to Venus or Mars. Space travel through such an immensity of emptiness is neither for us nor for our descendants.

So what is left? Perhaps only the search for signals from the inhabitants of planets of other stars in our galaxy. We can send signals and listen for answers, or we can assume that intelligent beings on those far-distant planets have already been signaling through space for ages past in the hope of receiving some response. Yet if we were to start signaling now by radio transmitters of sufficient power, it would take several hundred years for a radio message to reach a planet of stars such as Betelgeuse or Rigel, which are among the nearest possible planet-bearing stars. If a reply came back many generations later, we would have forgotten what was said in the first place. This difficulty of communication, supposing there is someone else at the other end, is what C. S. Lewis has called “God’s quarantine regulations.” Even so, the listening for signals possibly already sent in our direction has begun. The great radio telescopes, tuned in on the wavelength of the absorption band of hydrogen, are alerted to this possibility, on the principle that although the chances of receiving and then recognizing instellar signals may be almost nil, we should not let even so small a chance go by default. Meanwhile, we look to Mars with much hope and a certain amount of faith, for all that we shall ever know of life elsewhere than on earth may lie, so to speak, in our own backyard.