Contents

[chapter 1]

Background

The biological program of the National Aeronautics and Space Administration had a late start. A small life sciences group, organized in 1958, was concerned with life support and use of primates for system and vehicle testing for the Mercury program. Three small suborbital flights of biological materials were flown in space.

The Bioscience Program Office of the Office of Space Science and Applications was organized in 1962. The goals of the Bioscience Program are: (1) to determine if extraterrestrial life exists anywhere in the solar system and to study its origin, nature, and level of development, if it is present; (2) to determine the effects of space and planetary environments on Earth organisms, including man; (3) to conduct biological research to develop life support and protective measures for extended manned space flight; and (4) to develop fundamental theories in biology relative to origin, development, and relationship to environment. Research and development has been carried out to design life-detection experiments and instruments for future flights to Mars and to develop experiments to study the effects of the space environment on living organisms. A biosatellite program, started in 1963, has the first of six flights scheduled for 1966.

Space exploration has demanded a rigorous development, especially in the biosciences area. Investigation of the solar system for exotic life forms, the environmental extremes to which Earth organisms (including man) are being exposed, the possibilities for modification of planetary environments by biological techniques yet to be developed, and the problems of communication in biosystems are areas which have required refinement of the theoretical framework of biology before progress could be made rapidly enough to keep pace with technological advances in transportation.

Of all the sciences, biology alone has not yet benefited from comparisons with the universe beyond Earth. It is reasonable to suppose that breakthroughs might be made in biology on the basis of comparisons with life from other worlds. Organisms elsewhere may have found alternatives to processes we think of as basic characteristics of life.

In contrast, physical science has advanced sufficiently to provide a great body of laws which may be expressed in mathematical terms, and by which phenomena may be predicted with complete accuracy. A well-known characteristic of biological phenomena is variability. The Darwinian concept of evolution is perhaps the only pervading generalization in biology. This concept has been supported by evidence of a hereditary mechanism in the discovery of genes and gene mutations.

Space bioscience represents the convergence of main disciplines with a single orientation, whose direction is determined by the problems of manned space travel which have, in turn, created a host of bioengineering problems concerned with supporting man in space.

Foremost among these questions is the possibility of the existence of extraterrestrial life. The field which is concerned with the search for extraterrestrial life has come to be called "exobiology." In addition to the challenge of great technological problems which must be solved, exobiology is so closely related to the central scientific questions in biological science that it is considered by some to be the most significant pursuit in all of science.

One of the major opportunities already presented by the advances in propulsion systems is the ability to escape from the influence of the Earth, which has made possible the study of organism-environment relationships, particularly the role that environmental stimuli play in the establishment and maintenance of normal organization in living systems.

Transcending even these formidable objectives of space bioscience is an objective shared by all life sciences, the discovery of nature's scheme for coding the messages contained in biological molecules. Extraterrestrial biology seeks to find not only evidence of life now present, but the vestigial chemicals of its previous existence. The ways and means have already been made available to study molecules on whose long, recorded messages is written the autobiography of evolution—the history of living organisms extending back to the beginnings of life. On this same basis, it is now within the realm of science to foresee the means of predicting the development of life from primordial, nonliving chemical systems. Closely allied to the search for extraterrestrial life is research which seeks to identify the materials and the conditions which are the prerequisites of life.

Space bioscience research is now extending human knowledge of fundamental biological phenomena, both in space and on Earth, just as the physical sciences explore other aspects of the universe. The accomplishment of bioscience objectives is totally dependent upon advances in the technology of space flight. A highly developed launch-vehicle capability is essential to accomplish the long-duration missions required in the search for extraterrestrial life.

Life on other planets in the solar system (with emphasis on Mars) will be investigated by full exploitation of space technology which will allow both remote (orbiter) and direct (lander) observations of the planetary atmosphere, surface, and subsurface. Certain characteristics of terrestrial life, such as growth and reproduction, provide a basis for relatively simple experiments which may be used on early missions to detect the existence of life on Mars. Later missions will provide extensive automatic laboratory capabilities for analyzing many samples taken from various depths and locations. Because of the hypothetical nature of current experiment designs, it is likely that visual observations of the planet will be required. Many technical problems are involved in storing and transmitting the large amounts of data over planetary distances. Such visual observations might very well be crucial in interpreting results from other experiments. Critical to all exploration of the Moon and planets are the requirements to: (1) prevent contamination of the environment with Earth organisms and preserve the existing conditions of the planet for biological exploration; (2) provide strict quarantine for anything returned to Earth from the Moon and planets.

The biological exploration of Mars is a scientific undertaking of the greatest significance. Its realization will be a major milestone in the history of human achievement. The characterization of life, if present, and study of the evolutionary processes involved and their relationship to the evolution of terrestrial life would have a great scientific and philosophical impact. What is at stake is nothing less than knowledge of our place in nature.

Extended Earth orbital flights with subhuman specimens will be used to determine the effects on Earth organisms of prolonged weightlessness, radiation, and removal from the influence of the Earth's rotation. Such flights of biosatellites and other suitable spacecraft are expected to: (1) establish biological specifications for extending the duration of manned space flight; (2) provide a flexible means of testing unforeseen contingencies, thus providing an effective biological backup for manned missions; (3) yield experimental data more rapidly by virtue of the greater number and expendability of subjects; (4) anticipate possible delayed effects appearing in later life or in subsequent generations, through use of animal subjects with more rapid development and aging; (5) develop and test new physiological instrumentation techniques, surgical preparations, prophylactic techniques, and therapeutic procedures which are not possible on human subjects; and (6) provide a broad background of experience and data which will permit more accurate interpretations of observed effects of space flight on living organisms, including man.

[chapter 2]

Exobiology

The possibility of discovering an independent life form on a planet other than Earth presents an unequaled challenge in the history of scientific search. Therefore, the detection of life within the solar system is a major objective of space research in the foreseeable future.

The scientific data presently available concerning the possible existence of a Martian life form and the chemical constitution of the surface of Mars are disappointingly few. In fact, it is impossible to make a statement about any of the many surface features, other than the polar caps, with any degree of certainty. The observational results have been accounted for by many conflicting hypotheses which can only be resolved by the accumulation of new evidence.

The arguments supporting the existence of Martian life ([ref.1]) are based on the following observations:

  1. The various colors, including green, exhibited by the dark areas
  2. The seasonal changes in the visual albedo and polarization of the dark areas
  3. The ability of the dark areas to regenerate after an extensive "duststorm"
  4. The presence of absorption bands at 3.3µ-3.7µ, attributed to organic molecules

Conflicting interpretations of the above observations have been advanced. The argument based on the colors is inconclusive, and several workers have suggested that the color is a contrast effect with the bright-reddish continents. The meager quantitative data have been discussed by Öpik ([ref.2]) who has reduced Kozyrev's photometric observations of the very dark area of Syrtis Major to intrinsic reflectivities by allowing for the estimated atmospheric attenuation and reflectivity. Kuiper ([ref.3]) similarly demonstrated the absence of the near-infrared reflection maximum, which is characteristic of most green plants, indicating that chlorophyll was not responsible for the color.

The second and third arguments remain the most cogent. However, serious limitations are imposed on the second if the severity of the Martian climate is considered. Föcas ([ref.4]) has photometrically measured the seasonal changes in the fine structure of the dark areas of Mars and concludes that—

  1. The dark areas of Mars show periodic variation of intensity following the cycle of the darkening element
  2. The average intensity of the dark area, not including the action of the darkening waves, increases from the poles toward the equator
  3. The action of each of the darkening waves decreases from the poles toward the equator. This decrease is balanced in the equatorial zone by the combined action of the two darkening waves alternately originating at the two poles. The mechanism of the darkness-generating element seems to be constant for all latitudes during the Martian year.

The variation in intensity has been explained recently by nonlife mechanisms for Depressio Hellespontica (an area showing one of the greatest seasonal changes) ([ref.2]). Similar nonlife mechanisms may be applicable to the other dark regions, and, thus, the "darkening" can be used only as circumstantial evidence in support of a Martian life form.

If inorganic interpretations of the seasonal albedo variation are accepted, then an inorganic interpretation must also be advanced for the polarization variation. Two possibilities can be suggested:

  1. A change in surface texture, caused by varying absorption of atmospheric constituents, causing both the albedo and polarization to change in the manner observed
  2. A change in surface texture, in which the surface material becomes rougher, which also explains the observed polarization data ([ref.5])

The third argument against the regenerative feature of the dark areas being a life process has been advanced by Kuiper ([ref.6]). It is based on atmospheric circulation causing dust, presumably lava, to be blown on the dark areas of Mars during the late summer, autumn, and winter, and then removed during the spring. Mamikunian and Moore have recently advanced the similar explanation that carbonaceous chondrites or asteroidal matter may induce the observed phenomenon if they are abundant on the planet's surface. The pulverized chondritic material will exhibit a high degree of opacity due to localization and, hence, a change in polarization characteristics and a decrease in polarization following mixing of the chondritic material with indigenous surface minerals.

The fourth observational argument, the Sinton bands ([ref.7]), has been shown to be at least doubtful. Rea, Belsky, and Calvin ([ref.8]) recorded infrared reflection spectra for a large number of inorganic and organic samples, including minerals and biological specimens, for the purpose of interpreting the 3µ-to-1µ spectrum of Mars. These authors state that a previous suggestion that the Martian "bands" be attributed solely to carbohydrates is not a required conclusion. At the same time they fail to present a satisfactory alternate explanation, and the problem remains unsolved. More recently, Rea et al. ([ref.9]) noted the similarity between the 3.58µ and 3.69µ minima in the Martian infrared spectra and those of D2O-HDO-H2O mixtures and, particularly, of HDO.

With all this marked disagreement in interpreting the observational data concerning Mars, it becomes clearly evident that an experimental approach to the detection of life on Mars should provide the maximum positive information possible. Some life-detection experiments developed with NASA support have been summarized by Quimby ([ref.10]).

The schema of the biological exploration of a planet is to conduct a series of complementary experiments proceeding from general to specific. The general experiments will examine gross characteristics of the planet's environment and surface for determining the probability of an active biota (life). Data from the general experiments will be significant in—

  1. Defining the nature of specific experiments in which life detection is the major objective; and
  2. Providing a high degree of confidence in undertaking specific experiments, since indications from the gross characterization of the planet in question will influence the choice and design of the specific experiments.

The biological exploration of planets is then to be defined as the search for those parameters relevant to the origin, development, sustenance, and degradation of life in a planetary environment. This definition will give rise to a critical question for each progressively specific and complex experiment to determine—

  1. The existence of life on the planet
  2. The degree of similarity or dissimilarity (structure and function) with respect to terrestrial life
  3. The origin of this planetary life

The immediate objective of the biological explorations of the planet is to define the state of the planetary surface, which may exhibit the following properties:

  1. A prebiota (defined as the absence of life)
  2. An active biota (defined as the presence of life)
  3. An extinct biota (defined as evidence of former life)

The identification and the detailed characterization of each of the above stages of planetary development constitute the subject matter of the biological exploration of the planets and, specifically, Mars.