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On Mars: Exploration of the Red Planet. 1958-1978
 
 
THE RISE OF EXOBIOLOGY AS A DISCIPLINE
 
 
 
[54] As earth-bound biologists began to consider the existence-past or present-of life forms on other planets, two themes developed, detection [55] and protection. How do you detect something whose nature and existence are unknown? How do you protect one planet from contamination by the biota of another? Detection and protection of life in the solar system were the subjects of considerable debate and investigation during the decade (1959-1968) that preceded the selection of biology experiments for Viking. Concern about possible contamination of other bodies by terrestrial organisms that might stow away aboard space probes got an impetus with the launch of Sputnik in 1957.
 
 
Planetary Protection
 
 
Josh Lederberg was one of the first scientists to express publicly his worries about improperly sterilized spacecraft being the source of cosmic pollution. In 1961, he noted, "a corollary of interplanetary communication is the artificial dissemination of terrestrial life to new habitats." 10 His interest in planetary protection went back three years to the orbiting of Sputnik 1 .
 
On his way back to the United States from a year as a Fulbright lecturer in Melbourne, Australia, Lederberg stopped to visit for a few days with Haldane, who was teaching in Calcutta. Lederberg recorded his recollections of a dinner party given on 6 November 1957, an evening on which another Soviet space spectacular seemed likely in celebration of the 40th anniversary of the Russian Revolution.
 
The night of our arrival was the occasion of a lunar eclipse which was regarded as an important religious festival in Calcutta. It was also the occasion for a good deal of dinner table conversation... Many members of the group were quite strongly pro-Soviet in their inclinations and they were almost gleeful at the prospect that the Soviet Union would follow up its October 4th triumph with another launch, perhaps even directed at the moon during the lunar eclipse. So, [we] even stayed up to see if there would be such a demonstration although we were well aware of the physical difficulties of arranging for something that could be visible from earth. * That occasion led me to think very sharply about the extent to which political motives would outweigh scientific ones in the further development of the space program....11
 
When he returned to the University of Wisconsin where he was chairman of the medical genetics department, Lederberg circulated among the scientific community several editions of a memorandum expressing his concern over lunar and planetary contamination. His thoughts were subsequently formulated in a paper presented in May 1958 at the Satellite-Life Sciences Symposium, sponsored by the National Academy of Sciences, the [56] American Institute of Biological Sciences, and the National Science Foundation, and in an article for Science .12
 
At the National Academy of Sciences, Lederberg's interest further stimulated concern over possible biological contamination in outer space. The Academy noted that improperly sterilized spacecraft might "compromise and make impossible forever after critical scientific experiments." Resolutions adopted in February 1958 by the Academy Council urged scientists "to plan lunar and planetary studies with great care" and called for the International Council of Scientific Unions "to encourage and assist the evaluation of such contamination and the development of means for its prevention." The Academy further intended to participate in the planning of "lunar or planetary experiments....so as to prevent contamination of celestial objects in a way that would impair the unique....scientific opportunities."13
 
An ad hoc Committee on Contamination by Extraterrestrial Exploration, formed by the International Council of Scientific Unions, met in May 1958 to draw up a code of conduct that would permit lunar and planetary exploration but at the same time prevent contamination. After being circulated throughout the scientific community, the proposed standards were adopted in October 1958. During the remaining months of 1958 and throughout 1959, the International Council of Scientific Unions' Committee on Space Research (COSPAR) and the U.S. Space Science Board continued to develop guidelines for the sterilization of space probes.14
 
The Space Science Board also expanded its activities into the field of life sciences in 1959 as the board members became interested in experiments that would investigate "the viability of terrestrial life forms under extraterrestrial conditions" and the implications of contamination.15 The group's ad hoc committee on the subject, chaired by Lederberg, concluded that sterilization was technically feasible and that effective procedures could be developed, provided sufficient emphasis was given the problem. Toward that end, the Space Science Board sent suggestions to NASA and the Advanced Research Projects Agency on 14 September 1959. NASA Administrator Glennan assured the Space Science Board that the space agency had adopted the general policy of sterilizing, to the extent technically feasible, all space probes intended to pass in the near vicinity of or impact upon the moon or planets."16 Moveover, Abe Silverstein requested that JPL, Goddard Space Flight Center, and Space Technology Laboratories begin coordinated work on sterilization techniques.
 
While NASA Headquarters, its field centers, and contractors worked toward protecting the moon and planets from terrestrial microorganisms, the agency was studying more closely its participation in the life sciences.17 To determine NASA's role in that field, Glennan established an ad hoc Bioscience Advisory Committee in July 1959. Chaired by Seymour S. Kety of the Public Health Service, the advisory board ** reported 25 January 1960 [57] that life sciences had and would continue to have an important place in the American space program. The objectives of space research in this area were twofold-"(1) investigations of the effects extraterrestrial environments on living organisms including the search for extraterrestrial life; (2) scientific and technologic advances related to manned space flight and exploration." 18 Kety and his colleagues also noted that existing space-related life-science activities were important, but support of more basic research in the biological, medical, and behavioral sciences was more crucial.
 
Besides supporting an Office of Life Sciences at NASA and arguing vigorously for the complete independence of life-science research from the military, the committee urged the space agency to search for extraterrestrial life on Mars. Kety and his colleagues recognized that a basic study of extraterrestrial environments would further man's understanding of the fundamental laws of nature. The origin of life and the possibility of its presence elsewhere in the universe were indeed challenging issues.
 
For the first time in history, partial answers to these questions are within reach. Limited knowledge acquired over the past century concerning atmospheric and climatic conditions on other planets, the topographical and seasonal variety in color of the surface of Mars, the spectroscopic similaritiesŠhave suggested the presence of extraterrestrial environments suitable for life and permitted the formulation of hypotheses for the existence there of some forms of life at present or in the past.
 
The Kety committee believed that within the foreseeable future these hypotheses might be tested, indirectly at first by astronomical observations and by samplings taken mechanically from other planets, and finally by direct human exploration. The discovery of extraterrestrial life, or its absence, "will have important implications toward an ultimate understanding of biological phenomena."19 Although these specialists believed that biological studies would "not be complete until the scientist himself is able to make meticulous investigations on the spot," they realized that manned missions to Mars belonged to the distant future.
 
As NASA went about establishing its Office of Life Sciences in the spring of 1960, the agency found itself with a 10-year plan that called for planetary missions in 1962 and 1964 and a recommendation from the Bioscience Advisory Committee to search for life. Given the scientific interest in Mars and the apparent feasibility of sending probes to that planet by the mid-l960s, it would have been difficult to argue against the idea. In August 1960, NASA authorized JPL to study spacecraft concepts for a mission to the Red Planet, a mission that would land a capsule on the surface and initiate the search for life beyond Earth. Although the Kety committee in 1959 and the Space Science Board's summer study at Iowa State University in 1962 both called for the biological investigation of Mars, a 1964 summer study sponsored by NASA and the Space Science Board was a [58] further step in articulating the essential issues for exobiology as a field of inquiry.
 
 
1964 Summer Study
 
 
Professional biological interest in the search for life elsewhere in the universe had been growing for at least half a dozen years before the 1964 Summer Study gave exobiology the intellectual respectability needed to draw bright young scientists to the field. The "old-timers"-Lederberg, Colin Pittendrigh, and Wolf Vishniac, in their 30s and 40s-all had substantial and estimable careers in biology behind them before they launched into their quest for biota on Mars. Commenting on his early years in exobiology, Lederberg noted that his Nobel Prize for work on the genetics of bacteria had given him professional stability, which made it possible for him "to stay in a non-reputable game. Not disreputable, mind you, but non-reputable. It might have been very, very difficult otherwise and it would [have been] very hard for a capable young scientist who's had a lot of risks to take in his career to hitch it to something as uncertain as exobiology." 20 Gerald A. Soffen's experience is an example of the personal turmoil that could result from wishing to pursue the field of exobiology.
 
Jerry Soffen had begun his scientific career as a biologist. After earning a zoology undergraduate degree at the University of California in 1949, Soffen went on to study biology at the University of Southern California. Two books influenced the course of his subsequent career. One was A. I. Oparin's The Origin of Life . Soffen believed that Oparin was addressing himself to genesis-the origins of life, "the origins of me." Oparin's book started Soffen thinking about the beginnings of life, but Harold F. Blum's Time's Arrow and Evolution was even more influential. Blum's concept was simple and elegant-evolution conformed to the second law of thermodynamics. The universe's supply of energy is slowly diminishing, and all biological forms must adapt to lower, less satisfactory energy sources. Simple organisms present in a more primitive age when the oceans supplied them with a very rich nutrient broth had to develop more specialized and complex mechanisms for gathering energy (nutrients) as the ocean environment became less rich. Evolution is not a random process, since organisms must make orderly changes to survive in a changing world. This process leads to more complex, not simpler, organisms. Furthermore, organic evolution on Earth must be viewed as but a small part of the evolution of the entire universe. 21
 
Soffen was so overwhelmed by the philosophical implications of Blum's work that he went to Princeton to do his doctoral work under Blum. During his doctoral studies, Soffen heard Stanley Miller summarize his investigations into the origins of life on Earth. As were many of his contemporaries, Soffen was taken by the brilliance and simplicity of Miller's theory. But the crucial factor for Soffen was the dawn of the era of spaceflight. Men could now reasonably talk of exploring the planets, and the [59] search for life on other worlds was no longer just a dream. Soffen's interest in space exploration and the search for life on Mars brought him to another crossroads in his career while he was doing postdoctoral work at the New York State University School of Medicine in 1960.
 
Would Soffen pursue a safe, respectable career in biology studying mollusks, or would he gamble and undertake the study of exobiology, a new field not accepted as legitimate by many scientists? Soffen did not have fame or a Nobel Prize, as did Josh Lederberg, to give him academic security, and many professionals warned him against entering the new discipline. One physicist, Leo Szilard, told Soffen he was the wrong person from whom to seek advice. Instead, Soffen must ask himself what he wanted from life, no one else could decide the best course for him to follow. Soffen made his choice in 1961 when he joined the staff at the Jet Propulsion Laboratory, and he spent the next eight years managing the development of biological instruments, including exobiological detectors for spacecraft. 22 A wish to counter some of the professional risks associated with committing a career to exobiology was one of the reasons NASA convened the 1964 Summer Study at Stanford University.
 
After the usual staff work by Orr Reynold's Bioscience Programs Division, NASA got the summer study proposal moving by sending, in February 1964 over Homer Newell's signature, a letter to Chairman Harry Hess of the Space Science Board. Newell reminded Hess that "one of the prime assignments'' of the space agency was "the search for extraterrestrial life," and he noted that the report of the Iowa City Summer Study of 1962 also described this undertaking as "the most exciting, challenging, and profound issue not only of the century but of the whole naturalistic movement." 23 There were those within and without the space science community who would question that priority, but even the most skeptical admitted that the discovery of life on a distant planet would have scientific, sociological, and theological implications of the first magnitude. 24
 
Newell's letter set in motion a series of meetings between NASA and Space Science Board staff members. By mid-April, the board had readied its proposal for a summer study. Dean Colin Pittendrigh, professor of biology at Princeton, and Joshua Lederberg were appointed cochairmen of the study, and a distinguished group of scientists were named to the steering committee and the working group of participants for the June discussions (of the 37 persons who made up the core of the 1964 Summer Study, 9 would become key figures in the Viking Project.) The summer meetings provided a much-needed forum where scientists could advise NASA as to what research they wanted the agency to support.
 
Some, Lederberg among them, had begun to worry about relations between the Space Science Board and NASA. Such sessions as the one in 1964 at Stanford were important decision-making exercises. But who would participate in such studies other than the interested and the enthusiastic, he mused? Thus, he viewed their reports as basically reputable, authoritative, [60] and responsible endorsements, but also biased. While the views expressed that summer were generally those of proponents, the fact that they had been made publicly did achieve at least two things. First, the thinking of the participants who proposed a search for life on Mars had been sharpened, since their ideas were to be exposed to the critical evaluation of the larger scientific community. That is, those ideas became explicit targets for critical discussion. Second, the proposals had to be advanced in language that would permit broad discussion by legislators and laymen, as well. The study permitted NASA to discover how much scientific interest and support existed for the search for Martian life and to obtain the endorsement of the specialists for what the agency's advance planners wanted to do. Once a report with the Space Science Board-National Academy of Sciences imprimatur appeared, the space agency could move ahead. 25
 
Those who participated in the 1964 Summer Study were believers and enthusiasts. Basic to their inquiries was a wish to know if life on Earth was unique. They could not prejudge the likelihood of life on other planets. While a speculation that it might exist was a relatively reasonable one, the biological community had no firm basis for assuming that other planets would be either fertile or barren. According to the 1964 summer conferees, "At stake in this uncertainty is nothing less than knowledge of our place in nature. It is the major reason why the sudden opportunity to explore a neighboring planet for life is so immensely important. 26
 
Mars was a scientifically likely abode for life, the most Earthlike of all the planets. Although the Martian year was 687 days, the length of the day was "curiously similar to that of Earth, a fact that to a considerable degree ameliorates an otherwise very severe environment." The Red Planet had retained a tenuous atmosphere with surface pressures variously estimated from 10 to 80 millibars; the gaseous composition of that atmosphere was still a mystery in 1964. But scientists had concluded that oxygen was virtually nonexistent: "Oxygen has been sought but not detected; the sensitivity of measurement implies a proportion not greater than 0.1 per cent by volume." Water was also scarce. Water vapor had been measured spectroscopically with only traces detected in the atmosphere.
 
 
 

Table 6

Physical Properties, Mars and Earth (1964)

Property

Earth

Mars

Atmospheric pressure

1000 millibars

10 - 80 millibars

Gaseous composition:

oxygen

20.0%

< 00.1%

carbon dioxide

0.03%

5 - 30%

nitrogen

78.0%

60 - 95%

Water vapor

3 g cm2

2x10-3 g cm2

 
 

[61] On Mars, surface temperatures overlapped the range on Earth. At some latitudes, daily highs of +30°C had been measured, and ranges of 100° within a 4-hour period were not unknown. 27

 
But knowledge of the Martian surface had not progressed much beyond Lowell's observations at the beginning of the century. There was general agreement that the polar caps were frozen, but whether it was water or carbon dioxide was still a matter "of some controversy." Nor was there any understanding of a transport mechanism that could account for the seasonal alteration of the poles. "Our knowledge of what lies between the polar caps is limited to the distinction between the so-called 'dark' and 'bright' areas and their seasonal changes." The bright areas were generally believed to be deserts, with their "orange-ochre," or buff, appearance. The green color attributed to the darker regions was likely an optical illusion due to the contrast with the bright regions. Of biological interest were the seasonal changes in the dark areas. As was noted in the 1964 summer session report:
 
In several respects they exhibit the kind of seasonal change one would expect were they due so the presence of organisms absent in the "bright" (desert) areas. In spring, the recession of the ice cap is accomplished by development of a dark collar as its border, and as the spring advances a wave of darkening proceeds through the dark areas toward the equator and, in fact, overshoots it 20° into the opposite hemisphere. 28
 
The authors of Biology and the Exploration of Mars were quick to point out that the seasonal changes did not require the presence of living organisms. "Indeed, the question is whether the Martian environment could support life at all; and further, whether its history would have permitted the indigenous origin of life." Those were clearly two different questions.
 
One of the "more rewarding exercises" the summer study participants engaged in was the "challenge so construct a Martian ecology assuming the most adverse conditions indicated by present knowledge." That task posed no insuperable problems. Life forms could be conceived to exist with little or no oxygen. Some terrestrial organisms can survive freeze-thaw cycles of +30°C to -70°C. Others cope well with very low humidity, deriving their water supply metabolically. The intense ultraviolet radiation at the surface of Mars did not seem so be an insurmountable problem either, as some members of the study believed that organisms might exploit that radiation as an energy source. "The history of our own planet provides plenty of evidence that, once attained, living organization is capable of evolving adjustments so very extreme environments." 29
 
Does life in fact exist on Mars?-this was a question of a different sort. That life forms could subsist on the planet was no kind of proof that life had, actually emerged there. But the members of the study held that, "Given all the evidence presently available, we believe is entirely reasonable that Mars [62] is inhabited with living organisms and that life independently originated there. However, it should be clearly recognized that our conclusion that the biological exploration of Mars will be a rewarding venture does not depend upon the hypothesis of Martian life." Two essential scientific questions should not be prejudged:
 
a. Is terrestrial life unique? The discovery of Martian life, whether extant or extinct, would provide an unequivocal answer.
b. What is the geochemical (and geophysical) history of an Earth-like planet undisturbed by living organisms? If we discover that Mars is sterile we may find answers to this alternative and highly significant question. 30
 
 
Scientific Aims of Martian Exploration
 
 
Having established that Mars was a worthy object of study, the summer study scholars addressed the precise aims of an investigation. "We approach the prospect of Martian exploration as evolutionary biologists." Whereas the emergence of organisms "was a chapter in the natural history of the Earth's surface," these scientists sought to test the generalized hypothesis that the evolution of life "is a probable event in the evolution of all planetary crusts that resemble" the Earth. Thus, they conceived the overall exploration of Mars "as a systematic study of the evolution of the Martian surface and atmosphere [italics in original text throughout unless noted otherwise]." Their aims in the summary were:
 
(1) determination of the physical and chemical conditions of the Martian surface as a potential environment for life,
(2) determination whether life is or has been present on Mars,
(3) determination of the characteristics of that life, if present, and
(4) investigation of the pattern of chemical evolution without life. 31
 
As biologists, they had as "much interest as the planetary astronomers in a thorough study of the meteorology, geochemistry, geophysics and topography of Mars." Whatever the ultimate outcome of the search for life, its full meaning would be understood only within the broader context.
 
Four basic avenues of approach were suggested for the exploration of Mars, with the first three tasks ultimately leading to the fourth:
 
(a) laboratory work needed to develop techniques for planetary investigations and the knowledge needed to interpret their findings:
(b) Earth-bound astronomical studies of Mars:
(c) the use of spacecraft for the remote investigation of Mars; and
(d) a direct study of the Martian surface by landing missions. 32
 
[63] But by 1964, especially with the difficulties in planning Mariner B, it was apparent to all that defining lander payloads was a complex and demanding task."
 
The planners needed more information about the structure of the Red Planet's atmosphere. Would parachutes work? Would retrorockets be necessary? They hoped Mariner 3 and 4 , scheduled for launch in November 1964, would provide some answers on which spacecraft designers could base their plans. But even if complete knowledge for safely landing an instrumented package existed, the "principal design difficulty would remain: it concerns the problem of life detection. What minimal set of assays will permit us to detect Martian life if it does exist? A debate on this question for the past several years has yielded a variety of competing approaches." Each alternative was directed to monitoring some manifestation of life according to cues taken from terrestrial biology. An examination of life-detection concepts as they had evolved by 1964 provides an understanding of the problems facing the exobiologists, as well as the implied "Earth chauvinisms" 33 (a term popularized by Carl Sagan to describe the tendency to assume that living beings anywhere would be similar to those on Earth.)
 
The very first grant NASA made in the area of biological science was so Wolf Vishniac for $4485 to develop "a prototype instrument for the remote detection of microorganisms on other planets." This money, awarded in March 1959 for work on what became known as Wolf Trap, initiated research in the field of life detection. Vishniac and his colleagues realized immediately that they faced a difficult task. 34
 
Wolf Vladimir Vishniac was one of the pioneers in the search for extraterrestrial life. Born in Berlin in 1922, the son of Latvian parents who had fled the chaos of the Russian civil war, he was an associate professor of microbiology at the Yale University School of Medicine when he joined 18 other scientists*** 19-20 December 1958 at the Massachusetts Institute of Technology to discuss the problems of detecting life on other planets and the possibility of contaminating those distant environments. The group, which took the name Panel on Extraterrestrial Life (or EASTEX, to distinguish is from a West Coast group led by Lederberg and called WESTEX, which met during 1959 and 1960 at Stanford University and JPL), was jointly sponsored by the National Academy of Sciences-National Research Council and the Armed Forces Committee on Bioastronautics. Melvin Calvin, professor of chemistry at the University of California at Berkeley, and Vishniac served as chairman and vice-chairman of EASTEX through 1961. At that first meeting in December 1958, one of the basic questions [64] addressed by the physicists and biologists was what kinds of life forms they might reasonably expect to find away from their own planet. 35
 
Four basic hypotheses were advanced as to the nature of that life. One might find (1) living things that were essentially the same as those found on Earth; (2) life forms with the same chemistry but with peculiarities resulting from evolution in a different environment-both at the present and in the past-(3) organisms with a chemical base other than carbon (for example silicon, however unlikely that appeared in the "carbon chauvinistic" understanding of chemistry); or (4) very primitive life forms representing the initial steps along the evolutionary path. Two other distinct possibilities also existed-that life had evolved only on Earth and all the other planets were sterile, or that life had once flourished, or as least begun, on other planets only to succumb to environmental factors that precluded successful adaptation and evolution. In December 1958, few of the scientists gathered in Cambridge would have fervently backed one of these six possibilities over any other.
 
How does a scientist detect that which he is uncertain exists and whose form he is unsure of? Vishniac and his colleagues had to make some basic assumptions, and one of them was that life elsewhere would have a carbon base. Early in the 1960s, Vishniac in an interview said that scientists were "not acquainted with any forms of life except those that are carbon-based. It may be that carbon is indeed the only useful element that provides the structural basis for life, because of its chemical versatility.'' There was the possibility that other elements or combinations of elements might take on similar functions. "For instance, silicon-based life has been suggested-but silicon will not make as large and as stable compounds as will carbon. Compounds must be stable enough to....serve as structural units and to preserve some kind of continuity from generation to generation." Furthermore, a life-base compound must be reactive enough to permit metabolism to take place. "Carbon is particularly suited for that because is combines with itself, and with many other elements, perhaps to a greater extent than does any other element." Vishniac and others concluded that the simplest assumption was to say that life "always will be based on carbon. It may turn out that we are deluding ourselves-that we are simply limited in our imagination because of our limited experience." That was the constant intriguing possibility inherent in space research. 36
 
Accepting the assumption regarding carbon, the exobiologists were still faced with defining life forms. What is life? What is a living thing? Three NASA authors who sought to analyze the life-detection problem wrote:
 
The difficulties associated with assigning an unequivocal definition to the phenomenon of life lead one to utilize various approaches to a better understanding of the living state. From the standpoint of the problem of the detection of life on extraterrestrial bodies, it may be pertinent to list and scrutinize closely the criteria most commonly attributed to [65] living systems. Thus the initial task of the exobiologist is to describe life in such a manner that tests can be devised that can demonstrate, unequivocally, the existence of extraterrestrial life . 37
 
 
These three scientists suggested five accepted manifestations of life: growth, movement, irritability, reproduction, and metabolism. Taken together, they provided an indication of living organisms, but the early students of exobiology had to determine which of these manifestations were primary to their search for living forms on other planets, "especially if those forms are exclusively microbes, as is suspected by some to be the case for Mars." A second factor to consider was the kind of detectors that might be sent to the planets. Given weight and size limitations, detectors that would test for the existence of microbiological life forms seems more realistic than bulkier hardware created to locate larger organisms. 38
 
When the exobiologists began developing life detectors, they built on the foundation provided by modern genetic theory, especially that relating to the cell as a living system. During the 1950s had emerged the revolutionary concept that the storage and transfer of basic biological information took place within the cell. A cell was "visualized as a society of macromolecules, bound together by a complex system of communication regulating both their synthesis and their activity." 39 If the cell could store and transmit biological information, it had to be able to reproduce and metabolize. Reproduction is the process which maintains biological information by its constant renewal, Metabolism has been characterized as "the fire that genetic material keeps going outside itself, to get the other material to work for it, in the service of its own distinctive goal: its own survival and replication.'' 40 Therefore, the minimum requirements of life can be represented as an interdependence among macromolecules, metabolism, and reproduction.
 
The exobiologists examined each of the three attributes to determine its relevance to the problem of detecting life. Many scientists working with Earth-bound experiments assigned top priority to reproduction. While there was certainly no argument that life could not exist very long without it, the exobiologist found it a difficult phenomenon on which to base an extraterrestrial experiment. It is a discontinuous process and "the reproductive rate varies enormously from species to species and, depending on environmental conditions, often within the species." Even at the macromolecular level, reproduction (replication) is often discontinuous in many life forms. With all the factors known to complicate observations of the reproduction of life on Earth, the detection of reproduction of life "in an exotic situation could be extremely difficult." 41
 
Lederberg and others had proposed visual observations on Mars and Venus for microscopic and macroscopic life. But as with observations of reproduction, a living organism might not provide the scientist with motion or other visible clues during the short life span of an extraterrestrial experiment. The authors of the summer study report concluded that, as [66] attractive as the idea of visual observation was, "we can easily imagine circumstances in which this type of observation would be inconclusive." 42 A more reliable basis was needed.
 
Metabolism appeared the most promising attribute on which to base life-detection experiments, primarily because it was continuous process. "Even life forms that are considered to be in a highly inactive state (e.g., bacterial spores and plant seeds) carry on measurable, albeit extremely low, rates of metabolism." Metabolism also could be measured in several ways (changes in pH or temperature, the evolution of gases). But after "lengthy discussions and deep deliberation," the exobiological community agreed that "a truly meaningful life detection program must be based on [several] fundamental attributes of life." 43 Scientists would not be convinced by negative answers from any single life detector. They wanted some direct visual inspection by television and a program that would land an automated biological laboratory (ABL). While not fully defined in 1964, the ABL would permit a number of chemical analyses and a variety of biological experiments. Plans included an onboard computer by which a variety of programmed assay sequences could be initiated, contingent on results of prior steps, and a sustained discourse between the computer and investigators on Earth. By remote control of their mechanical surrogate, the scientists on Earth could carry out investigations much as they would in their terrestrial laboratories. It was "in short an ambitious concept," but "realizable with current technology." 44
 
 
Mechanisms for Detecting Life on Mars
 
 
There was no shortage of life-detection concepts. 45 Speaking to this point at the beginning of the summer study on 15 June 1964, Lederberg compared the Mars life-search to the work that he and his colleagues normally did in their laboratories. In their everyday biochemical experiments, they were limited by approaches and hardware. Similarly, in the proposed exobiological studies, they needed to focus on the target and think about the best collective experiments for some years hence. The basic problem would come to deciding which instruments to develop. Scientists could quickly think of many experiments that might be done. 46 Once the redundant ideas were eliminated, a reasonable number of practical-looking concepts remained, among which were several that NASA had supported over the past several years. But translation of concepts into hardware was a challenge. In May 1963, NASA's Ames Research Center, Moffett Field, California, had been assigned the task of evaluating the many exobiology experiments. Ames had been serving as NASA's "in-house" life science research laboratory since the arrival of Richard S. Young in 1960, and in 1962 an Exobiology Division was established there. Hence, scientists at Ames were familiar with the issues the exobiologists were addressing their experiments to. 47
 
[67] Mars Surface Television . "The first thing man generally does in a new and strange environment is to look around." That was exactly what scientists wanted to do through one of the large Voyager-class landers, using television to view the topography immediately surrounding the craft. "There may be both geologic and biological surprises in the landscapeŠ" Television pictures would also permit the mission team to check out and monitor the condition of the lander. And not to be overlooked was the public-relations value of pictures as scientists and laymen alike shared a closeup view of Martian scenery. 48
 
Vidicon Microscopes . A more sophisticated use of television cameras was the proposed microscope-television combination. Based on the suggestion of Joshua Lederberg, this idea was being pursued as=t his Instrument Research Laboratory at Stanford and in Gerald Soffen's facility at the Jet Propulsion Lab. "The detection of life by looking for it sounds elementary; however, this seemingly simple technique is extremely complex and involves numerous technical problems." Stanford and JPL scientists and instrument-makers were confronted by the difficulty and uncertainty in recognition and identification of microorganisms by microscope. 49 Beyond that, the large information return required to produce pictures of suitable quality appeared to be beyond computer capabilities projected for Mariner 1966. Although the Ames life-detection experiments team rejected the vidicon microscope for the Mariner flight, members of the summer study believed it had sufficient merit to be considered for a 1971 mission like Voyager. 50
 
Wolf Trap . Wolf Vishniac originally developed this device in 1958- 1960 to demonstrate the feasibility of automatic remote detection of the growth of microorganisms. He wanted to prove that such an instrument could be built, and having once committed himself to the experiment he seemed unable to set it aside for other ideas that might have been more fruitful. Defending this first exobiological instrument became part of Vishniac's promotional work on behalf of the Mars biology program. 51
 
In a 1960 issue of Aerospace Medicine , Vishniac explained that microorganisms "are responsible for the major amount of turnover of matter on earth and...life of the higher plants and animals is inconceivable in [their] absence." 52 The object of Wolf Trap was the growth of Martian microbes, if they existed and could be trapped. At the heart of the instrument was a growth chamber with an acidity (pH) detector and light sensor; the former would sense the changes in acidity that almost inevitably accompany the growth of microorganisms, while the latter would measure the changes in the amount of light passing through the growth chamber, Microorganisms, such as bacteria, turn a clear culture medium cloudy (turbid) as they grow, and the light sensor would detect such changes. The pH measurement would complement the turbidity measurement, providing an independent check on growth and metabolism.
 
 
 
 
[68] (A vidicon microscope, January 1965, being considered for future use in seeking extraterrestrial life had no moving parts. An aerosol for carrying particles was injected into the instrument and onto the impaction plate through a nozzle in the condenser lens. The objective lens and lamp were fixed in relation to the plane of focus. The sample was collected through a gas-operated aerosol aspirator.) [Note: labels for this picture had to be rewritten for them to display properly- Chris Gamble, html editor].
 
 
 
By mid-1963 Vishniac, with the assistance of C. R. Wilson and others, had progressed from a simple feasibility model to a more complex bread-board**** design. A contract with Ball Brothers Research Corporation for the development of the second-generation instrument was let by the University of Rochester in 1961. Late In 1963, the Ames life-detection experiments team report noted several problems still unresolved, notably the likelihood of false signs of growth resulting from the sampling technique, and said the experiment probably could not be ready for 1966 but might be a 1969 candidate. 53
 
Multivator . Conceived by Joshua Lederberg and worked out in prototype form by Elliott Levinthal and his assistants in the Instrumentation Research Laboratory at the Stanford School of Medicine, multivator was intended to be a miniature multipurpose biochemical laboratory in which a....
 
 
Model of Wolf Trap life detection device with cover removed. [Note: labels for this picture had to be rewritten for them to display properly- Chris Gamble, html editor].
 
[69]....series of simple measurements could be made on samples of atmospheric dust. A variety of measurements was studied, and they all included testing a small sample of dust with a fluid reagent and reading out a simple optical or electrometric measurement. Lederberg and his associates originally hoped to cultivate Martian microorganisms in a defined culture medium, as in Wolf Trap, but they concluded that the brief communication times between a Mars lander and Earth monitoring stations would limit the opportunities of observing changes based on growth. Enzymatic activity might be a more realistic behavior to study. Thus, they began to concentrate on detecting the action of enymatic phosphatase on phosphate containing chemicals that become fluorescent following removal of the phosphate grout. When enzymatic activity took place, the resulting glow would be determined by a detector, perhaps photoelectrically. 54 The Ames team evaluating the multivator in August 1963 decided that the instrument was maturing rapidly but that the experiments it would house would require "a great deal more effort" before they would be ready to be sent off on a mission to Mars. 55
 
Minivator . A variant on the multivator concept, devised by Jerry L. Stuart of JPL, minivator had an improved sample-collection device. Driven by gas-powered turbine, the sample collector separated large and small particles by centrifugal action. Again, the instrument development was ahead of work on the experiments it would house. The Ames team assumed that the best features of the multivator and minivator would be combined. 56
 
Gulliver . Named after Jonathan Swift's fictional traveler to strange places, the Gulliver instrument was the work of Gilbert V. Levin. After many years in the public health field, where he sought better methods for detecting bacterial contaminants in polluted water, Levin asked T. Keith Glennan, NASA's first administrator, if the agency would be interested in developing life-detection instruments for use on space probes. A contract for the work was let in l961. 57
 
Gulliver consisted of a culture chamber into which a sample of soil could be introduced. In the chamber was a broth whose organic nutrients were labeled with radioactive carbon. If microorganisms were put into the broth, they would metabolize the organic compounds, releasing radioactive carbon dioxide that could be trapped on a chemically coated film at the window of a Geiger counter. The radioactivity readings would be relayed to Earth by the spacecraft's radio transmitter. Gulliver had the virtue of being able to detect growth, as well as metabolism, since the rate of carbon dioxide production would increase exponentially with growing cultures.
 
Sample acquisition was the early Gulliver's unique feature. The instrument had a mechanism consisting of two 7.5-meter lengths of kite line wound around small projectiles in the manner of harpoon lines to prevent snagging. The string was coated with a sterile silicone grease to make it sticky. After the lander arrived on Mars, the projectiles would be....
 
 
 
 
[whole page 70] (Multivator Chambers, Multivator, above in January 1965, was a miniature laboratory for biochemical experiments on Mars. Gulliver III, at left, also in January, carried sticky strings and projectiles to be fired and retrieved with dust and loose particles to be tested for production of carbon dioxide indicating life.)
 
 
[71]....fired in mortar fashion and then reeled in together with adhering soil particles. After the lines were retrieved. Gulliver would be sealed and an ampule broken, releasing the sterile radioactive nutrients onto the samples.
 
The Ames life-detection experiments team gave Gulliver high marks because, unlike other experiments of the time, it had a sampling mechanism. But they also raised questions about the nature of the technique, since samples delivered to the growth and control chambers would not be identical. The chambers would contain a metabolic poison to serve as a check on chemically produced radioactive carbon that might otherwise be interpreted as signs of metabolism, and experimental control to prevent false results required a common sampling source. The Ames team concluded that sample acquisition might be a problem. It further noted that Gulliver was the most advanced experiment in terms of hardware development and the only one likely to be ready for flight in 1966. 58 Other life-detection concepts are listed in table 7.
 
Given the conclusion that no single life detector would be sufficiently accurate and conclusive in its results, an automated biological laboratory containing several experiments was the prudent choice. But before such sophisticated. expensive hardware was landed on Mars, a successful orbiter program was necessary; scientists and engineers needed more data regarding the planet's atmosphere (density and chemical composition) and surface. An orbiter's sustained seasonal observations would permit thorough evaluation of features considered suggestive of life and a better informed selection of landing sites for the laboratory.
 
 

 
(Cutaway view of a gas chromatograph, January 1965) [Note: labels for this picture had to be rewritten for them to display properly- Chris Gamble, html editor].
 
[Note: the two tables below should be next to each other, Chris Gamble, html editor].
 

[pp72-73] Table 7

Ames Life-Detection Team Evaluation of Proposed Biology Instruments-Development Status, 1963

Experiment

Status

Date Available

Manpower Support to Meet 1966 Date

Monetary Support to Meet 1966 Date

Vidicon microscope

Science-conceptual.

?

?

?

Device-none.

Wolf trap
Lab leasibility model. Engineering is conceptual.
April 1966
Univ.of Rochester will need 1 Ph.D. & 4 techs. Subcontractor requirements unknown.

Double present funding.

 

Multivator

Science-functional feasibility.

?

Sufficient available.

Sufficient available.

Device-conceptual.

1 Sept. 1963

Sufficient available.

$10 000 for development of Mark 11. $200 000 for flight hardware.

Minivator

Science-none.

-

-

-

Device-flight-sized breadboard.

Now

3 engineers.
4 technicians.
$200 000 for flight prototype. $40 000 for test & evaluation.
Gulliver

Advanced bread-board demonstrated. Ready to start work on prototype.

With proper funding and interface definition, 1 yr from contract award.

10 persons required in engineering area

 

Between $250 000 and $350 000, depending on required experiment configuration

Optical rotation

Some functional feasibility demonstrated.

14 mos from contract start.

-

$274 652

"J" band

Science-functional feasibility.

1 Aug. 1963.

2 scientists.
4 tethnicians.

$100 000

Device-conceptual.

1 Aug. 1964 for flight prototype.

8-10 persons 1 yr.

$300 000-400 000

Gas chromatograph

Feasibility breadboard.

Nov. 1964.

Additional: 4 engineers and 5 technicians.

$425 000

Mass spectrometer

Conceptual.

May be ready 1966 launch date.

2 assistants for Dr. Biemann and services of Consolidated Systems Corp.

$350 000

 
 

Table 7 (continued)

Ames Life-Detection Team Evaluation of Proposed Biology Instruments-Development Status, 1963 (continued)

Experiment

Comments

Weight (kg)
Volume
(cu cm)

Power requirement (av/peak, watts)

Possible lifetime
Sterilizable
by 150°C
for 24 hrs

Vadicon microscope

Data rate requirements demand power available only with much larger boosters. Development of sample handling, methods for discrimination of biologicals requires more work.

Not defined
Not defined

10

Not defined

Yes

Wolf trap

1.1-2.3

2460 - 3280

0.25/1

10-hr minimum

Yes

Multivator

Depends on stability of phosphatase assay substrate.
Can accomodate wide variety of biochemical experiments including some already proposed.

1.4

1558

0.5/3-5

Days-week

Yes

Minivator

Science input lacking; accommodation similar to Multivator.

2.3

Not defined

1-2/5-10

2 weeks

Yes

Gulliver

-

3.2 - 5.4

4920 - 9840

2-3/4-5

Not defined

Yes

Optical rotation

-

2.4

2132

0.5/1.1

Not defined

Yes

"J" band

Sample acquisition and handlin,g development not begun.

Not defined

Not defined

2-3/10

Weeks

Yes

Gas chromatograph

-

3.04

3280

?/14.5

Not defined

Yes

Mass spectrometer

Support requirements appear to be underestimated by experimenter.

-

-

-

-

-

 
Source: Based on data presented in NASA. Ames Research Cemer, Life-Detection Experiments Team, ''A Survey of Life-Detection Experiments for Mars," Aug. 1963, pp. 70-71.
 
 
[74] When looking into automated biological laboratories, the summer study group had to consider how such advanced landers would be scheduled in relation to Mariner flights. Mariner flyby spacecraft were slated for launch in November 1964 by Atlas-Agena. Replacing the ill-fated Mariner B, Mariners E and F, approved in December 1963 for combination flyby and probe missions, were planned for 1966 (as Mariner 1966) if Atlas-Centaur were operational by that time. Thus, the members of the 1964 Summer Study preferred "a gradualistic approach" to the ultimate goals of landing a large automated laboratory on Mars and eventually returning samples for study. The scientific community favored exhausting all avenues of research, Earth-based observations and nonlanding missions, before committing itself to that big step.
 
However, the summer study members saw several "constraints to proceeding in a completely unhurried step-by-step fashion," Those included a "combination of celestial mechanics and the operational realities of space research." Preparation for flight required years of experimental design and spacecraft development and the coordination of effort among large numbers of persons in a wide range of disciplines, As individual scientists, accustomed to following their own idiosyncratic process of trial and error in designing laboratory experiments. they found the world of space research filled with tightly controlled schedules and very specific dos and don'ts. They noted further that the scientist was "plagued by the prospect of investing years of work only to encounter a mission failure or cancellation in which it is all lost-at least until a new opportunity arises, perhaps years hence," While the scientists might "chafe under these circumstances," it was the nature of the enterprise.
 
Added to the technological and scientific limitations was the small number of launch opportunities for flights to Mars. The "attempt to develop a systematic and gradualistic program is thus constrained to some extent by the fact that, while favorable opportunities occur in the 1969-1973 period, they will not return before 1984-1985." Therefore the summer study members argued for "a substantial program" that would exploit the Saturn launch vehicles during the 1969-1973 launch window. Explicit in their recommendations was concentration on activities that would lead to landings. "The first landing mission should be scheduled no later than 1973, and by 1971 if possible. 59
 
* Ironically, Jet Propulsion Laboratory proposed detonation of an atomic bomb on the lunar surface in response to the orbiting of Sputnik. William H. Pickering to Lee A. DuBridge, with summary of Red Socks proposal, 25 Oct. 1957, JPLHF 2-581.
 
** Other members included W. O. Fenn, D. R. Goddard, D. G. Marquis, R. S. Morison, C. T. Randt, and C. A. Tobias.
 
*** Dean Cowie, Carnegie Institute of Washington; Richard Davies, JPL; George A. Derbyshire, Space Science Board; Paul M. Doty, Thomas Gold, W. R. Sistrom, and Fred L. Whipple, Harvard; H. Keffer Hartline, Rockefeller Institute; Martin Kamen, University of California, San Diego, Cyrus Levinthal, Bruno B. Rossi, and A. Luria, MIT; E. F. MacNichol, Johns Hopkins; Stanley Miller, Columbia; John W. Townsend, Jr., NASA; Bruce H. Billings, Baird-Atomic, Inc.; Herbert Freeman, Servo-Mechanisms Laboratory; and Richard S. Young, Army Ordnance Missile Command.
 
**** An assembly of parts used to prove the workability of a device or principle without regard to the final configuration or packaging of the parts.