Chapter 6L
LIFE IN SPACE: THE COMPLETE STORY?
Astrobiology and what I have called space biology proper do not exhaust the possibilities that space offers to the life sciences. Those possibilities extend to many areas in which our understanding of life may have profound consequences for our interaction with nature. I would like to conclude this chapter by considering briefly three novel areas of investigation.
The first may be called planetary biology, or perhaps global biology. So far I have discussed our attempts to understand micro-organisms, plants, and animals. But we also wish to understand the living environment as a whole and in relation to the other components of the global environment. Planetary biology attempts to achieve this by means of interdisciplinary research that makes extensive use of space techniques for atmospheric sampling and remote sensing. From the remarks made in Chapter 4 it is clear that the study of the role of bacteria and plants in the global environment fits in nicely with the aims of planetary science. Planetary biology expands the scope of investigation and makes the relationship to general planetary science all that more evident. One of its initial aims is to trace the flow of nitrogen and sulfur in the marine environment off the coast of California, and to determine the mechanisms by which different compounds of these elements are converted into others.[1] The eventual goal of this new field is quite ambitious. In Harold Klein's words, it is "to treat the planet as an ecosystem and try to understand the laws of this ecosystem."[2]
A second area of investigation involves the construction of closed environments in space. Until now we have not built any really closed environments up there -- natural wastes are thrown into space, not recycled as on the Earth, oxygen is lost to the vacuum, and so on.[3] Furthermore, the balance of those environments is maintained by artificial means. Whether we can ever built living closed environments in space is a matter of controversy. Indeed, at this time we cannot even determine the minimum size required for a naturally self-sustaining environment amenable to Earth life. But in trying to build one we may learn much. In fact, even artificially closed environments may teach us valuable lessons about terrestrial ecology.
There are several obstacles that limit severely the knowledge we can obtain about an ecological system. One of them is that the amount of variables involved, most of which are interrelated, is simply unmanageable. And even when this obstacle is overcome, the victory seldom lasts long. Normally, a model of a system accounts for changes in one part of the system by changing the amount of reaction in other parts. More sophisticated models may go as far as predicting the rate of such reaction. The problem is that, when confronted with different circumstances, organisms sometimes change not just the amount and rate but the modality of reaction. This problem is illustrated by two examples from a report of the National Academy of Sciences entitled Life Beyond the Earth's Environment: "...many bacteria will use available nitrogen if it is present but in its absence become fixers of nitrogen from the air. Brown hydra in competition with green hydra will, in the presence of abundant food, eat their competitors, and in the absence of abundant food, will float away to some new location leaving the area to the green hydra alone."[4]
Another problem is that a complete description of an ecosystem often requires that we count the numbers of each kind of organism in order to ascertain what it contributes to the flux of matter and energy of that ecosystem. But such counting, for example of worms in the soil, in many cases destroys the ecosystem we are merely trying to describe.
A suggestion for getting around these problems is that we test models of the system in closed versions of it. These models would not attempt to represent every element of the system -- which would be practically impossible -- but would be based instead on a list of the species present and on the roles played by the species presumed to dominate the system. The suggestion is that we build closed environments in accordance with one such model, and then partition them in a variety of ways. We can learn from the interruptions in the normal flows and cycles of the system what its crucial factors are. By disturbing or interrupting the cycle of nutrients, for example, many species may starve while their food accumulates elsewhere, and others may be poisoned by the concentration of toxic wastes that normally would have been washed away. Of course, these partitions do not only take away from the system, in some cases they add to it; just as a dam that interrupts the flow of a river creates a habitat favorable to a variety of organisms that would have been at a disadvantage otherwise.
Intelligent manipulation of this ecology of failure offers the prospect of many exciting questions and experiments. But on Earth there are two serious limitations. One is that the only completely closed system is the Earth itself, which, though open to energy, is relatively closed to matter. Partial closure is of course satisfactory for many investigations, but in some cases we may need greater experimental control. Another limitation is that some closures may be dangerous or undesirable (they may produce very toxic substances, for example). Space offers an opportunity to achieve perfect closure in many investigations that cry out for it; it also permits us to carry out some of the most dangerous experiments in capsules safely isolated from our home planet.
An apparent limitation of space is that larger and richer environments cannot be easily recreated. But there is a sense in which this limitation becomes an advantage. An increased manned presence in space means a greater complexity of man-made habitats, perhaps with a serious attempt to create space agriculture. But this would automatically require that as the ecosystem gets larger we learn more and more about what the crucial flows and cycles are and what it takes to maintain them. A lunar base, for example, can be viewed as an experiment to determine the degree to which environmental sufficiency can be achieved. And a Martian colony may be in a good position to experiment with a variety of environments for agriculture, since the red planet is rich in resources and the colonists may thus have many choices in the composition of such environments. Gerard O'Neill's space colonies may have an even greater potential.
A third area of promise is the invention of new tools to investigate the basic levels of organisms. This point seldom receives the attention it deserves. The absence of gravity permits the development of experimental techniques that are either very difficult or plain impossible on the surface of the planet. I will mention a few ideas that have been suggested over the years, just to catch the flavor of the possibilities.
The technique of electrophoresis, which was described in Chapter 2, can become a useful tool for the production of pure drugs. But its real potential may be found in research instead. For example, our metabolic processes are controlled by about 2,000 enzymes, of which as many as one hundred are mixtures of isozymes. With electrophoresis, we can separate and study those isozymes. If nothing else we can vastly improve our diagnostic skills in matters concerning imbalances and disorders of the human body.
And I think there is reason to believe that this use of electrophoresis in space may herald a new generation of analytical tools for biologists and medical researchers. And that reason is simply that by removing gravity we may not only gain much in purity but also take advantage of the fine operation of electric currents. Some of this fine operation already pays dividends on Earth. Using weak pulsed electric fields, for instance, it is possible to induce cells to fuse, a technique that leads to very unusual new cells. It can be used, among other things, to fuse tumor cells with the spleen cells that produce the specific antibodies that could destroy the tumor if there were only enough of them. The value of one of these fused cells (hybridomas) is that it will make many copies of itself (clones). And all of these copies will produce the same antibody of the original spleen cell, but now in large amounts, we hope, to get rid of the tumor once and for all. I do not know whether this very technique will prove feasible in space.[5] But others kindred to it may find in the advantages of space (purity, effective use of weak currents) the right spark to ignite a new explosion in biomedical research.
Many tools for medical research, and many new medical technologies may come from physics instead. According to an article by John Tierney:
The Russians invented an air scrubber using strong electric fields and cold-plasma chambers to prevent biological contamination of the air in the MIR space station. Now the French-based firm AirlnSpace, with support from the European Space Agency, have refined the Russian invention to create the portable “Inmunair.” According to the firm’s general manager, the system successfully screened anthrax and small-pox substitutes in laboratory tests.[6]
These three areas are mere examples. I have neither the expertise nor the imagination to evaluate all the promise of space biology. Suffice it to say, for now, that space biology is in a position to ask not only new questions but also new kinds of questions. In this, like the rest of space science, it fulfills the function of preserving the dynamic character of science. Some of space biology, the search for origins in particular, merits its pursuit as a main goal. Space biology proper, as I have called it, is in its theoretical and experimental infancy, and will probably have to ride as a passenger of other space undertakings. Nevertheless I have given reasons why it is worth supporting in its own right. For the time being, it can be considered as one of the benefits that come to us from the general exploration of space.
[1] For example, to what extent is dymethyl sulfide produced by marine algae?
[2] Harold Klein, "The Biological Sciences and NASA," NASA Advisory Council Talk, May 1983, p.5 of the text.
[3] For a discussion of these issues see Life Beyond the Earth's Environment, a report of the Space Science Board of the National Academy of Sciences, 1979 (section in ecology, pp. 105-132); R.M. Mason, J.L. Carden, eds., Controlled Ecological Life Support System: Research and Development Guidelines, NASA CP-2232, 1982; B. Moore III and R.D. MacElroy, Controlled Ecological Life Support System: Biological Problems, NASA CP-2233, 1982; and B. Moore III, R.A. Wharton, R.D. MacElroy, eds., Controlled Ecological Life Support Systems: First Principal Investigators Meeting, NASA CP-2247, 1982.
[4] Life Beyond the Earth's Environment, ibid., p.111.
[5] There are three problems with this technique as a weapon against cancer. One is the difficulty in the formation of hybridomas. In this, weak currents offer some advantages over competing technologies. My guess is that these advantages would be even more apparent in microgravity. A second problem is the stability of the hybridomas. In this, the record of microgravity experimentation should offer some encouragement. The third problem is the selection of the appropriate spleen cell to fuse with the tumor. In this, space does not offer special advantages, unless we consider the possibility of refined techniques of separation and identification.
[6] John Tierney, “Outer Space on Earth: NASA Should Try It,” reprinted in Detroit Free Press, August 2, 2005, p. 7A. Tierney’s derogatory comments are limited to the Space Shuttle. He does believe that much worthwhile scientific exploration can be done otherwise.
Posts
