by David Toomey
* Perhaps the best-known examples of such life were imagined by a British schoolteacher named Edwin A. Abbott. His 1888 Flatland: A Romance of Many Dimensions is the autobiography of “A. Square,” a two-dimensional being who inhabits a two-dimensional universe that he calls, for the convenience of his three-dimensional readers, “Flatland.” A. Square’s education regarding worlds of various dimensions is greatly assisted through analogies with dimensions below his own—that is, Pointland and Lineland—and Abbott’s readers in the third dimension are thereby invited to draw corresponding analogies to dimensions above their own. Flatland and most of its imaginative reworkings are mathematical fantasies and enjoyable exercises in geometry, and not intended to depict possible organisms or worlds.
* If we return for a moment to Bostrom’s argument for the probability that we are simulations, and if those simulators share a weakness for the weird, then it follows that we are weird life—weird, that is, in the view of our simulators.
* There is a difference of opinion split along the same disciplinary lines on the question of the probability of extraterrestrial intelligence. It was articulated perhaps most succinctly in a debate between Carl Sagan and Ernst Mayr, with Sagan taking the view that extraterrestrial intelligence was common, Mayr that it was rare and perhaps unique to our own species. Mayr observed that Sagan and others who estimated large numbers of extraterrestrial civilizations used a flawed reasoning attributable to their professional backgrounds: “When one looks at their qualifications, one finds that they are almost exclusively astronomers, physicists and engineers. They are simply unaware of the fact that the success of any SETI effort is not a matter of physical laws and engineering capabilities but essentially a matter of biological and sociological factors. These, quite obviously, have been entirely left out of the calculations of the possible success of any SETI project.” (http://www.astro.umass.edu/~mhanner/Lecture_Notes/Sagan-Mayr.pdf)
Epilogue
At present, no one has discovered an example of weird life, and it’s possible that no one ever will. For these reasons the subject resists the kind of tidy conclusion customary in an epilogue. But I can at least address the prospects for searches.
Although Davies and others have advocated a program for a set of dedicated and systematic searches for weird life on Earth, at present there is no such program. As described in the text, individual studies have sought weird life on Earth deliberately, and one may yet find it; but it’s also possible that the scientists who discover weird life on Earth do it, as it were, accidentally, while looking for something else. As to in situ searches for weird life on other worlds, they are a long way off at best. The only mission now under way to perform on-site study of any planet or moon’s surface is NASA’s Mars Science Laboratory, and it is designed to detect not life itself, but merely the conditions that would make life possible. Moreover, because mission scientists are defining those conditions as the ones suitable to life we know, the mission could fail to notice evidence of weird life. Although ESA has plans for a mission that will visit Jupiter and its moons, it is not designed specifically to seek life. No missions to the surfaces of two worlds high on the wish lists of astrobiologists—namely, Saturn’s moons Enceladus and Titan—are currently being developed.
Norman Pace observes that the first evidence for extraterrestrial life is likely to come from spectroscopic detection of chemical disequilibrium in the atmospheres of planets or moons in our Solar System or, more probably, outside it.1 Here, the numbers of both the research programs and the subjects being studied may vastly increase the odds. The mission of the Kepler space observatory, originally scheduled to end in November 2012, may be extended by two years, and perhaps two years beyond that. The mission of the COROT spacecraft (overseen by France’s National Center for Space Studies in cooperation with ESA), like the mission of Kepler, is the detection of planets by the transits, and it is ongoing. Roughly eighty programs for detecting extrasolar planets with Earthbound telescopes are either ongoing or in development,2 and many of them can perform spectroscopic analysis of planetary atmospheres. In advocating for a search for weird life, the NRC report noted that although the biosignatures of weird life in planetary atmospheres would be different from the biosignatures of life like our own, they could be detected just as readily.3 Of course, as mentioned in the text, without on-site study or a sample return it would be impossible to know for certain whether they were real biosignatures, or merely the product of some very unusual chemistry.
In the meantime, as we’ve seen, scientists are speculating, hypothesizing, and building models of weird biochemistry. Such thinking is valuable simply as an exercise, as noted some 300 years ago by Christiaan Huygens:
If anyone shall gravely tell me that I have spent my time idly in a vain and fruitless inquiry after what I can never become sure of, the answer is that at this rate he would put down all natural philosophy, as far as it concerns itself in searching into the nature of things. In such noble and sublime studies as these, ’tis a glory to arrive at probability, and the search itself rewards the pains.4
But thinking seriously about weird life has other uses too, as it helps scientists escape and overturn Kuhnian paradigms, expect the unexpected, and prepare themselves to recognize what their training and experience have not taught them to recognize.
It is possible that SETI will detect that long-sought signal. Otherwise, the first extraterrestrial life that humans encounter and can prove to be living is likely to be found with sophisticated remote-controlled spacecraft performing on-site studies, or sample-return missions. Since simple single-celled life arises more easily than complex life, odds are that the life encountered will be microbial. Suppose that it is weird. Upon hearing the news and seeing an image of a microbe that seems indistinguishable from any other, some will surely wonder what the fuss is about. To fully appreciate the discovery’s importance, many of us will need a refresher in biology—most probably a good thing.
Already, hypothesizing about weird life has contributed, albeit indirectly, to our appreciation and understanding of the part of the natural world we know exists. Many scientists who have hypothesized weird organisms made a case for their feasibility by noting parallels with familiar life. The layering of desert varnish (that candidate for weird life) is like the layering of stromatolites. Sagan and Saltpeter’s hypothesized Jovian ecology of hydrogen-breathing dirigibles is borrowed from the known ecology of microfauna in sunlit waters of Earth. And Dyson and Hoyle’s ideas of living interstellar clouds of dust grains and complex molecules organized by electromagnetic forces are modeled on neurotransmitters in animal brains. To make cases for the viability of these parallels, they have had to revisit the familiar.
The features of life we know continue to surprise biologists on a regular basis. And familiar life in all its variety still inspires imagination, reminding us how much of it remains undiscovered and unstudied. During an age in which many are increasingly disconnected from the natural world, an appreciation of that world from a fresh perspective is no small matter. If that is all the search for weird life ever gives us, it may be enough.
Glossary
aerosol A fine aerial suspension of liquid (mist or fog) or solid (dust or smoke) particles.
amino acid An organic compound; an essential component of the protein molecule.
Archaea One of the three largest groups, termed “domains,” in the three-domain system, the taxonomy introduced in the 1960s by microbiologist Carl Woese. The majority of extremophiles, as well as the most extreme extremophiles, belong to this domain. In the five-kingdom system, the same organisms are classified within the kingdom Bacteria as “archaebacteria.”
astrobiology Also termed exobiology and, less commonly, bioastronomy. The study of extraterrestrial life (all of which, as this book goes to press, is hypothetical) and the conditions that might make such life possible. More recently, the study of life in the context of the universe.
bacteria Microscopic single-celled o
rganisms lacking nuclear membranes around the genes and/or nucleus. All bacteria are prokaryotes. In Carl Woese’s three-domain system, they constitute the domain Bacteria.
bioastronomy See astrobiology.
biochemistry The chemistry of biological substances and processes.
biology The study of living organisms and life processes, including their structure, functioning, growth, origin, evolution, and distribution.
biosolvent A liquid medium that allows and facilitates chemical reactions conducive to life.
biosphere All life on Earth, existing in a region measured from upper levels of the atmosphere to several kilometers below the planet’s surface. The precise upper and lower limits of the biosphere have yet to be determined.
catalyst A substance that speeds the rate of a reaction by providing a lower-energy alternative pathway.
cell The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semipermeable membrane.
chemistry The study of the composition, structure, properties, and reactions of matter.
chirality Handedness; a configuration of any molecule that prevents it from interacting biochemically with mirror images of itself.
chromosome A (usually rod-shaped) structure that carries genes.
convergent evolution An increase in the degree of similarity between two or more unrelated species as they evolve.
cosmological constant A term, introduced by Einstein into the field equations of general relativity, that allowed for a static universe, neither expanding nor contracting.
cytoplasm The contents outside of the nucleus and enclosed within the cell membrane of a cell. The cytoplasm is clear in color and has a gel-like appearance. Composed mainly of water, it also contains enzymes, salts, and various organic molecules.
DNA Deoxyribonucleic acid. The fundamental hereditary material of all living organisms that biologists know of; the large molecule that composes genes.
ecology The study of the interaction of organisms with their environment.
ecosystem The organisms living in a particular environment, and the physical part of the environment that affects them and/or impinges on them.
Eukarya One of the three largest groups, termed “domains,” in the three-domain system, the taxonomy introduced in the 1960s by microbiologist Carl Woese.
eukaryotes Organisms (both microscopic and macroscopic) made of cells with membranes enclosing their genes and/or nucleus. They include protists (such as algae and slime molds) as well as fungi, plants, and animals. Compare to prokaryotes.
exobiology See astrobiology.
extremophile An organism that thrives under extreme environmental conditions of heat, pressure, pH, and so on. They include thermophiles, hyperthermophiles, psychrophiles or cryophiles, barophiles or piezophiles, acidophiles, alkaliphiles, halophiles, and radiophiles.
Gaia hypothesis The proposition that all organisms and their inorganic surroundings on Earth compose a single and self-regulating system that maintains conditions suitable for life.
gene The basic unit of heredity.
Goldilocks zone See habitable zone.
habitable zone Also termed Goldilocks zone. The region around a star within which it is theoretically possible for a planet with sufficient atmospheric pressure to maintain liquid water on its surface. More recently, the region anywhere (including interiors of planets and moons and other celestial bodies) where water might exist in liquid form.
hypothesis A scientific proposition that is supported by observational evidence and purports to explain a given phenomenon or set of phenomena. A hypothesis is neither as comprehensive nor as well established as a theory, although a set of related hypotheses may, over time, come to constitute a theory.
last universal common ancestor (LUCA) The theoretical organism from which all life is descended.
mesophile An organism that grows best in moderate temperatures, typically between 20°C and 45°C.
metabolism The sum of the physical and chemical processes that occur in a living organism.
methanogen An organism capable of producing methane from the decomposition of organic material.
microbe A microorganism.
microbial community A highly organized and well-integrated system of microbes that modifies its environment chemically and physically.
microbiology The scientific study of microscopic organisms.
multiverse The (hypothetical) set of all universes that results from one of several scenarios, including the “many-worlds” approach to quantum mechanics; versions of the “inflationary” hypothesis, in which universes are sprung from separate big bangs into different regions of space-time; and the “ultimate-ensemble” hypothesis, in which our universe is a mathematical structure and other universes are other mathematical structures.
organelle An organized structure within a cell.
organic Denoting or relating to chemical compounds containing carbon.
panspermia The theory that life on Earth and/or other suitable habitats originated on another world and arrived from outer space.
prebiotic Occurring before life appeared.
prokaryotes Organisms lacking nuclear membranes around the genes and/or nucleus. Most prokaryotes are bacteria. Compare to eukaryotes.
protein Any group of complex organic compounds consisting essentially of amino acids.
quantum mechanics Also termed quantum physics. The laws of physics that explain the behavior of the universe on very small scales (the scales of molecules, atoms, and electrons) and underlie the universe on larger scales. The laws that account in some way for vacuum fluctuations, the wave-particle duality, and various phenomena described by the Heisenberg uncertainty principle.
ribosome An assemblage of RNA and protein found in the cytoplasm of living cells and active in the synthesis of proteins.
RNA Ribonucleic acid.
shadow biosphere A hypothetical biosphere composed of weird life.
silane Any of a group of silicon hydrides, analogous to paraffin hydrocarbons and having the general formula SiH.
spore A microorganism in a dormant or resting state.
symbiosis The interaction of two organisms, typically to their mutual advantage.
synthetic biology Engineering of biological components or systems that are not known to nature; also, the reengineering of existing biological components.
taxonomy The science of classifying organisms.
theory A set of hypotheses that are supported by observational evidence and purport to explain a phenomenon or set of phenomena.
vertebrate Any animal with a backbone of bony segments enclosing the central nerve cord. The five major vertebrate groups are fishes, amphibians, reptiles, birds, and mammals.
vesicle A bladderlike cavity or sac, especially one filled with fluid.
virus An organized set of chemicals that is capable of reproduction and evolution but not of metabolism, and so is considered by most biologists not to be a living organism.
Notes
PROLOGUE
1. Margaret W. Robinson, Fictitious Beasts: A Bibliography (London: Library Association, 1961).
2. Wilson, Future of Life, 14.
3. Bryson, Short History, 322.
4. Lee, Vegetable Lamb of Tartary.
5. Hooke, Micrographia, 210.
6. Sattler, Puxbaum, and Psenner, “Bacterial Growth.”
7. Funch and Kristensen, “Cycliophora Is a New Phylum.”
8. National Research Council. Committee on the Limits of Organic Life in Planetary Systems, The Limits of Organic Life in Planetary Systems (Washington, DC: National Academies Press, 2007).
CHAPTER ONE: EXTREMOPHILES
1. Interview with the author, March 19, 2010.
2. In truth, my joshing here is unearned. There is a great deal to be excited about, especially recently. Samples of sediment from off the coast of Newfoundland sug
gest that bacteria and archaea may survive 1,600 meters below the seafloor, thus extending the biosphere deeper than many had imagined possible. Further, such sediment may contain as much as two-thirds of the Earth’s prokaryotic biomass by weight. See Roussel et al., “Extending the Sub-Sea-Floor Biosphere.”
3. Interview with the author, March 19, 2010.
4. Edmond and Von Damm, “Hot Springs,” 86.
5. Bryson, Short History, 274.
6. Piccard and Dietz, Seven Miles Down, 173.
7. Gross, Life on the Edge, 23.
8. The oxygen, it should be noted, is produced by phytoplankton, meaning that a part of this process depends, indirectly but ultimately, on photosynthesis.
9. Brock, “Road to Yellowstone.”
10. Stanier, Dondoroff, and Adelberg, Microbial World.
11. Kuhn, Structure of Scientific Revolutions, 63–64.
12. Ibid., 64.
13. MacElroy, “Some Comments.”
14. Stetter, “Hyperthermophilic Procaryotes.”
15. If one defines extremophiles as organisms adapted to environments hostile to life and takes the long view, you and I might well be included. The first life on Earth was anaerobic; it would have found oxygen to be toxic. In fact, although oxygen makes possible a more efficient metabolism, that efficiency may come at a cost. Cellular damage from oxygen has been implicated as a contributing cause of aging and cancer.
16. “Although they are rare, some environments with liquid water do not appear to support life; they include water over 400°C at submarine hydrothermal vents [and] high-brine liquid water found in sea-ice inclusions at –30°C.” But even in these extremes, microbes have been known to survive. (National Research Council, Limits of Organic Life, 31)
17. Kidd, Adaptation of External Nature.
18. Chung, “How Bug Extends.”
19. National Research Council, Limits of Organic Life, 35.
20. There is at least one interesting exception (Wharton and Ferns, “Survival of Intracellular Freezing”).
