The Search for Life That Is Very, Very Different From Our Own
By David Toomey
268 pp. W. W. Norton & Company. $25.95 (Amazon)
It’s life, Jim, but not as we know it. The familiar phrase, apocryphally attributed to “Star Trek,” encapsulates David Toomey’s study of the search for species flourishing in places where life was thought to be insupportable. “Weird Life” is a breakneck tour through natural history, encounters of an impossible kind, researchers as weird as the organisms they pursue that leads the reader to wonder where science ends and fantasy begins.
The story begins very much down to earth. The discovery of a hidden microbial world within our own planet’s ecosystems is not many decades old. Life, of a very odd sort, is much more ubiquitous than was once thought. Some micro-organisms thrive in boiling water under pressure; others feed on sulfur, salt, deadly poisonous elements, even radioactivity. Toomey describes one fungus found in the “water core of the Chernobyl nuclear reactor, ingeniously and fearlessly converting nuclear radiation into usable energy and managing radiation damage by keeping copies of the same chromosome in every cell.” “Extremophiles” can be found living in ice, under the sea floor, multiplying in clouds or huddled implausibly deep beneath the ground in a newly discovered geological biosphere. These tiny cells — a pinhead would be a world to them — do not look particularly spectacular. Most of them are just minute rods that grow by fission. But they are chemical factories of extraordinary versatility. As one distinguished microbiologist has put it, if they can find a way of grabbing an electron, they evolve to do so. Nobody knows how many species of extremophiles there are, and many more wait to be discovered, which should be exciting enough.
But what is already known is even more remarkable: for all their mysteriousness these tiny strangers share an ancestor with all us everyday weeds, butterflies and mammals. The extremophiles represent alternative, carbon-based life paths that diverged from the rest of existence more than three billion years ago. Some biologists believe that these microbes resemble our common ancestor, because they were adapted to an early Earth very different from the gentle Gaia we have today. They lurk in inhospitable corners and are tough enough to survive space travel, which leads to thoughts of life on Earth being seeded from elsewhere. Perhaps extremophiles are more than just strange anomalies. Toomey’s journey is about to leave Earth and head for the planets and the stars beyond.
Mars is the first stop. The thought that life might have been introduced from the red planet is far from new. Bill Clinton endorsed the possibility of life on Mars in 1996, but this claim has since been called into question. Nonetheless, there are probably places where extreme extremophiles from Earth could still prosper near its icy poles. But the search must move on, and here the science starts to merge with science fiction. It is certainly possible that the space probe Kepler has now detected numerous Earthlike planets circulating other stars in the galaxy, and some of them must be just the right distance from their own suns to be suitable for life. Lou Allamandola, the founder and director of the Astrophysics and Astrochemistry Laboratory at NASA’s Ames Research Center, is replicating in the laboratory the conditions on comet’s tails, showing how complex organic compounds might be synthesized there. But then. . . .
We are used to thinking of life based upon the distinctive properties of carbon and water. It does not have to be like that, according to astrobiologists. Life probably requires solvents, and a way for complex molecules to be built up: a prerequisite for self-replication that is one of life’s essential features. However, out on Titan (a moon of Saturn) there is liquid methane in which life could arise and whole new biochemical pathways could be imagined. A National Research Council report concludes: “If life is an intrinsic property of chemical reactivity, life should exist on Titan.”
But why stop there? On Triton (a moon of Neptune), where temperatures are so low that gases liquefy, a metabolism based on strange silica compounds and liquid nitrogen has been posited. Or again, astrobiologists have proposed life in the clouds surrounding Venus, and based on sulfuric acid. Why not life around red dwarfs if one tweaks the elements in a different fashion? Or in the multiverses that allegedly exist alongside our own universe, but through an impenetrable curtain? Or near absolute zero? Life — or at least theoretical life — seems to be possible almost everywhere and at all times by Toomey’s account. Even on the edges of black holes.
There is a real problem with these speculations if they are to be regarded as scientific hypotheses, and Toomey gives them far too easy a ride. He does know about Karl Popper’s distinction between science and metaphysics, because it appears in a footnote in his book: science, Popper holds, is testable and falsifiable. Virtually all the fun speculations of the astrobiologists would fail these stringent but necessary criteria. Provided the chemistry and physics are plausible, just about any bio-creation is presented as scientifically justified. The trouble is that they are not yet capable of being falsified, or indeed testable by experiment. It must be a tremendously enjoyable intellectual exercise paddling around in the seas of faraway worlds imagining life as a mist, or life that takes three millenniums to form a thought, or life based on liquid nitrogen. But it is not science. It is playful imagination.
This leads to the interesting notion that the only difference between science and science fiction in astrobiology is who says what. If the creature from outer space comes from the pen of Ursula K. Le Guin, it is science fiction, whereas if it is Carl Sagan (he of the Jovian “floaters”), it must be science. Where predictions have been made of weird life in an earthly system — like claims of arsenical life in Lake Mono — they have quickly been brought to account and sent packing. Provably wrong ideas in science get banished to an amnesiac world. A playful imagination might suggest that they are free to interbreed there and generate new life-forms. Science, Jim, but not as we know it.
All of which brings us to money. Science proceeds by fashion as much as by necessity, and astrobiology is fashionable, which is doubtless why Toomey followed it as a topic. Meanwhile, on planet Earth it’s estimated that 86 percent of all species — weird or not — have not been discovered, described or named. As the naturalists who might do so are themselves becoming rarer and rarer, it is hard not to regret the funds flying to the untestable reaches of space, when so much remains to be discovered among real, living, carbon-based organisms here on boring old Earth.