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On Mars: Exploration of the Red Planet. 1958-1978
 
 
THE RESULTS OF MARINER 4
 
 
 
[74] Whereas 1964 was a year of optimism for the burgeoning field of exobiology, 1965 was one of external criticism and reappraisal. New scientific information provided by the Mariner 4 flyby mission altered perceptions of the Red Planet and raised serious questions about the search for life there. Criticism of NASA's exobiology program came from two quarters, [75] members of the Mariner 4 science team and scientists who were critical of the space program in general terms.
 
Variously known during its developmental phase as Mariner C. Mariner M. and Mariner 1964, Mariner 4 was one of two spacecraft launched for Mars in 1964. Conceived in mid-1962 when NASA's advanced planners realized that the Centaur stage would not be ready for a 1964 mission, Mariner C was planned as a lighter Agena-sized spacecraft capable of a mission to Mars. As Mariner 2 to Venus in 1962 had been a scaled-down Mariner A, the 1964 Mars craft was a revision of Mariner B without the lander. 60 Although smaller than either NASA or the scientists would have preferred, it would provide the first photographs of Mars, an exciting prospect. From November 1962 when the Project Approval Document was signed to liftoff of the two craft in November 1964, this first Mars mission was a challenging exercise. Constant battles against growing payload weights and difficulties with perfecting scientific instruments added a `hectic air to preparations for the 1964 flights. 61
 
As the launch date approached, trouble seemed to be the key word, Mariner 3 was launched toward Mars about midday on 5 November. After a short delay while Agena circuits and relays were retested, the launch went normally, but an hour later telemetry indicated that while the scientific instruments were on there was no indication of power from the solar panels. Quickly the launch team determined that the cylindrical fiberglass nose fairing designed to protect the spacecraft during its initial ascent had failed to separate from it. Efforts to break the spacecraft free were frustrated when its circuits went dead after the batteries were drained. As Mariner 3 blindly headed out into space, destined to enter solar orbit, NASA and contractor personnel searched for the cause of the problem and a quick solution before the 25th, the scheduled date for the second launch. 62
 
Working around the clock for 17 days, a composite team from Lewis Research Center, Lockheed Missiles & Space Company, and JPL modified the nose fairing and produced a flawless launch of the second spacecraft on 28 November. 63 Everything went according to plan with Mariner 4 . The Agena D separated from the Atlas at an altitude of 185 kilometers and went into a parking orbit, After coasting for more than 30 minutes, the Agena engine fired again and Mariner was on the path to Mars. With only 45 minutes elapsed since liftoff from Cape Canaveral, Mariner 4 separated from Agena and continued its journey through space alone.
 
It took seven and a half months to travel the 525 million kilometers to Earth's neighbor. The 260-kilogram spacecraft began its brief encounter with the planet on 14 July 1965. Among other measurements, the vidicon television system during a 25-minute sequence took 21 full pictures and a fraction of a 22d of the Martian surface at distances of 10 000 to 17 000 kilometers. After being stored overnight on a tape recorder, the images were transmitted to Earth the next day. For eight and a half hours, JPL received....
 
 

 

 
[76] ( Mariner 4, above, is prepared for a center-of-gravity test at Jet Propulsion Laboratory. At right, the spacecraft starts on its way from Kennedy Space Center on 28 November 1964.)
 
 
 
....bits of electronic data that would be reconstructed into visual images. The pictures revealed a heavily cratered Mars. 64
 
What could one learn from 2l 1/2 pictures of l percent of the Martian surface taken from an average distance of 13000 kilometers? For Mariner 4, expectations helped color perceptions. On 11 January 1965, Robert B. Leighton, principal investigator for the television experiment and professor of physics at the California Institute of Technology, had written Glenn A. Reiff, Mariner project manager, commenting that the Mariner 4 pictures would "be of enormous interest to the scientific community and the public at large,'' but proper interpretation of those pictures was as important as their initial acquisition. 65 From the outset, NASA and JPL officials had carefully informed the public that Mariner would not produce pictures of sufficient resolution to detect plant or animal life, but while reporters told their audiences that "the pictures are not expected to resolve the mystery of life on Mars," they would usually add such phrases as "but may answer long standing questions about the 'canals' of the red planet," hinting that Mariner 4 's photography might indeed be spectacular. 66
 
[77] Before and during the flight, scores of articles about Mariner 4 , the 1964 Summer Study, exobiology, Voyager, and other aspects of the exploration of Mars appeared in the American press. 67 Most carried the caveat that the 20-some photos would be equivalent to the best telescopic views of the moon from Earth and that "even the broadest earth river would not be visible at such a distance," but writers argued that it might still be possible to view the irrigated bands along the canals if any existed on Mars. 68 Mariner 4 would not necessarily detect life, but the scientific community hoped it would provide additional insights into the likelihood of Martian biology. David Hoffman of the New York Herald Tribune commented on this dichotomy in an article on 14 July, the day the pictures were taken: "In what almost amounts to a non sequintur, NASA says the photo mission is not designed to answer 'the question of life on Mars.' But only to 'shed light on the possibility of extraterrestrial life." 69
 
For believers in Martian canals and for scientists dedicated to the extraterrestrial life search, the pictures were disappointing. In a 29 July 1965 statement, the Mars television team led by Leighton summarized their first thoughts on the significance of the photographs: "Man's first close-up look at Mars had revealed the scientifically startling fact that at least part of its surface is covered with large craters. Although the existence of Martian craters is clearly demonstrated beyond question, their meaning and significance is, of course, a matter of interpretation.'' Their opinion was that the craters led "to far-reaching fundamental inferences concerning the evolutionary history of Mars and further enhances the uniqueness of Earth within the solar system.'' Seventy craters were clearly visible in photos 5 through 15, and they ranged in diameter from 4.8 to 120 kilometers. NASA specialists noted that it seemed likely that there were both larger and smaller craters in addition to those discerned in the photos. The rims of the craters appeared to rise as much as 100 meters above the surface, and the interiors seemed to descend to several hundred meters. The number of large craters was closely comparable to the densely cratered upland areas of the moon. They added that no Earth-like features, such as mountain chains, great valleys, ocean basins, or continental plates, were identifiable in the small region sampled by Mariner 4 . And certainly no canals were seen.
 
From the pictures, the TV team thought some fundamental inferences could be drawn:
 
l. In terms of its evolutionary history, Mars is more Moon-like than Earth-like. Nonetheless, because it has an atmosphere, Mars may shed much light on early phases of Earth's history.
 
2. Reasoning by analogy with the Moon, much of the heavily cratered surface of Mars must be very ancient-perhaps two to five billion years old.
 
3. The remarkable state of preservation of such an ancient surface leads us to the inference that no atmosphere significantly denser than the present very thin one had characterized the planet since that surface was formed.
 
 

[whole page 78] (Mariner 4 revealed a heavily cratered Mars, more like the moon than like Earth. Photos taken 14 July 1965, just before the closest approach of 9700 kilometers, were radioed back as digital data. At top left, Mare Sirenum, bordering on Atlantis. Above, Atlantis between Mare Sirenum and Mare Cimmerium. At left, bright region, northwestern Phaethontis. Below at the White House 31 July 1964, JPL Director William Pickering shows Ranger 8 photo of the moon to President Johnson. NASA Associate Administrator for Space Science and Applications Homer E. Newell is with him. Behind the president are Dr. Donald F. Horning, special assistant to the president for science and technology, and Dr. Edward C. Welsh, executive secretary, National Aeronautics and Space Council.)

 

 

[79] Similarly, it is difficult to believe that free water in quantities sufficient to form streams or to fill oceans could have existed anywhere on Mars since that time. The presence of such amounts of water (and consequent atmosphere) would have caused severe erosion over the entire surface.
 
4. The principal topographic features of Mars photographed by Mariner have not been produced by stress and deformation originating within the planet, in distinction to the case of the Earth. Earth is internally dynamic giving rise to mountains, continents, and other such features, while evidently Mars has long been inactive. The lack of internal activity is also consistent with the absence of a significant magnetic field on Mars as was determined by the Mariner magnetometer experiment.
 
5. As we had anticipated, Mariner photos neither demonstrate nor preclude the possible existence of life on Mars. The search for a fossil record does appear less promising if Martian oceans never existed. On the other hand. if the Martian surface is truly in its primitive form, the surface may prove to be the best-perhaps the only-place in the solar system still preserving clues to original organic development, traces of which have long since disappeared from Earth. 70
 
The fifth point notwithstanding, the findings of the TV team were a genuine blow to the exobiologists. Leighton, Cal Tech astronomers Bruce C. Murray and Robert C. Sharp, and JPL television experts Richard K. Sloan and J. Denton Allen presented an official report in the 6 August 1965 issue of Science, restating the same basic conclusions. The apparent absence of water over hundreds of millions of years, the very thin atmosphere, and extremely low temperatures were strong arguments against the hypothesis for life put forward during the 1964 Summer Study. New tabular data for the physical properties of Mars are shown in table 8.
 
 
 

Table 8

Physical Properties of Mars: Mariner 4 Findings

Earth
Mars
(1964 Summer Study)
Mars 1
Mars 2
Mars 3

(alternative Mariner 4 figures)

Atmospheric pressure

1000 millibars

10-30 Millibars

4.1 - 5.7

4.1 - 6.2

5.0 - 7.0

Gaseous composition of atmopshere:

oxygen

20%

< .01%

-

-

-

carbon

0.03%

5 - 30%

100%

80%

50%

nitrogen

78%

60 - 95%

-

20% a

-

argon

trace

trace

-

-

50%

Temperature range

58°C to -88°C

+30°C to ±50°C

-93°C to ±20°C

-98°C to ±25°C

-103°C to ±20°C

 
a Nitrogen plus argon.
Source: NASA, Mariner-Mars 1964: Final Project Report, NASA SP-139 (Washington, 1967), pp321-22.
 
 
[80] No matter which of the alternative atmospheric estimates from Mariner 4 readings one chose, the possibility for life, past or present, seemed diminished. 71
 
 
External Criticism of the Search for Life on Mars
 
 
Criticism of the American space program, latent for several years, burst forth in 1963-1965. The two most prominent fault-finders were Barry Commoner, a microbiologist at Washington University, St. Louis, and critic-at-large-of-scientific priorities; and Philip H. Abelson, a physicist and the editor of Science . Both scientists, long-time critics of Apollo's lunar goals, extended their remarks to the exploration of Mars.
 
Commoner attacked the search for extraterrestrial life in June 1963 on the eve of Abelson's appearance before the Senate Astronautical and Space Science Committee. The committee was seeking "Scientists' Testimony on Space Goals," and Commoner noted that Abelson was the only witness expected to express reservations about the nation's priorities in space research. Of the 10 who were scheduled to testify, all but Abelson had a direct financial interest in the space program.* While Abelson attacked Apollo specifically, Commoner was upset by the argument that the extraterrestrial life search was "the most exciting, challenging and profound issue ... that has characterized the history of Western thought for 300 years.'" Believing the possibility of life on other planets was extraordinarily low, he thought that such rhetoric was "a weak prop for the serious decision given its profound economic and social consequences." 72
 
Scientists Commoner and Abelson did not agree with NASA's scientific goals. Simply put, they would have preferred to spend Apollo and Mariner-Voyager dollars on other investigations, They were also worried about the "social consequences" of space research in a world that was underfed and potentially revolutionary. In a September 1963 speech to the American Psychological Association, Abelson said there were no predictable economic advantages to be derived from the exploration of the moon or Mars, arguing that "the half of the world that is undernourished could scarcely be expected to place a higher value on landing on the moon than on filling their stomachs." 73
 
The exobiologists were accustomed to defending their work on scientific grounds, but they were understandably perplexed when they were criticized in a manner that combined scientific disagreements and differences in opinion over social and economic priorities. Lederberg and others were reasonably certain of Commoner's political motivations, but they were not sure of his scientific views, as he diverged from the origin-of-life hypothesis that underpinned the search for extraterrestrial life. Was it [81] scientist Commoner or social-critic Commoner who opposed the extraterrestrial search? 74
 
Abelson was even more difficult to understand. He was a long-time student of the extraterrestrial life question. In 1960, he had advised NASA that of all the near planets only Mars was a likely abode for life, but that the risk of contaminating the planet with Earth life-forms precluded our going there. By the next year, however, he was arguing persuasively that no place in our solar system other than Earth could support life as we know it. Thus, his editorial in the 2 February 1965 issue of Science , "the voice of American science," was particularly telling: "In looking for life on Mars we could establish for ourselves the reputation of being the greatest Simple Simons of all time." 75 Using the latest scientific information from Mariner 4 . Abelson built a case against future expenditures of tax dollars to look for life on Mars; he was convinced life did not exist there. For a mixture of scientific and political motives, he effectively used Science as a forum for the scientifically based denunciation of NASA's goals. 76
 
 
1964 Summer Study Revisited; or "Postscript: October 1965"
 
 
Against this background of scientific and political criticism, the discouraging new information provided by Mariner 4 posed serious questions for those who believed that there might be life on Mars and that continuation of the search was respectable and worthwhile. Joshua Lederberg later looked back on October 1965 as a bleak time for exobiology. With most of the scientific community in agreement with a New York Times editorial saying that "Mars is probably a dead planet," only a few "diehards" (Lederberg's description of his associates of the 1964 Summer Study) refused to give up and accept Mars as a barren world. 77 In a postscript to Biology and the Exploration of Mars , those diehards held that, "during the interval between publication in March 1965 of the Summary and Conclusions of our Study and the appearance of this volume, our knowledge of Mars has been raised loan entirely new level by the success of the Mariner IV mission," 78 Lederberg and 25 other "desperate" persons met in late October 1965 to discuss the impact of Mariner 4 on their proposed search for life: "The essence of our position was, and still is, the immense scientific importance of evaluating the uniqueness of life on Earth; of discovering facts that will permit more valid inference of its abundance in the Universe; and the fact that the new space technology allows us to obtain empirical evidence on the frequency with which living organization and its precursors emerge in the evolutionary history of planets." Even with the new Mariner data in hand, the scientists still thought "that life, even in essentially terrestrial form, could very well have originated on Mars and have survived in some of its contemporary micro-environments," While finding life clinging to the side of an inactive volcano or at the edge of some warm spring on Mars would be difficult, it was not totally unreasonable to expect. 79
 
There was another justification for going to the Red Planet. The summer study participants believed it was "important tore-emphasize....[82] a major aspect of our position that critics have unaccountably missed; we sought to emphasize that our conclusion that the biological exploration of Mars will be a rewarding venture does not depend upon the hypothesis of Martian life." Throughout their deliberations, they had cast their questions in the broad context of the general evolutionary process in nature. "Our position isŠfully justified even if life has not emerged there; but we will again be misunderstood if that emphasis is taken to mean we believe the chance of discovering fully fledged life is negligible." 80
 
At the end of 1965, the scientists who believed that looking for life on Mars was a respectable enterprise faced those who were equally devoted to the proposition that such an exercise was foolishness of the gravest order. Voyager, with its goal of placing automated biology laboratories on Mars, would become the focus of the two groups' debate, Voyager would be scrutinized because of costs and general disenchantment with the space program, but the central issue would continue to he the validity of searching for life on the Red Planet. To that issue, scientists could bring only informed speculations. Mariner 4 had provided only clues, no one could yet say with certainty that Mars was lifeless. And the search continued.
 
* The other nine were S. Ramo, H. C. Urey, P. Kursh, C. S. Pittendrigh, F. Seitz, L. V. Berkner, L. A. DuBridge, M. Schwarzchild, and H. H. Hess.