Back in 1984, meteorite hunters discovered a collection of rocks in the Allan Hills region of Antarctica believed to be from Mars. The rocks had been there for about 13,000 years, according to scientists. How the rocks got to Earth was uncertain. Some speculated their arrival at the South Pole was precipitated by a meteorite striking Mars millions of years before, sending a spray of Martian rocks and soil towards Earth.
One of the rocks—“ALH84001”—was especially interesting. Various tests indicated it left Mars at a time when the planet had liquid water on its surface. Readers may recall that the rock was intensively studied and discussed in 1996, when preliminary studies from electron microscopy showed what looked like fossilized microbes. Newspapers carried photos of the Martian “germs”, and President Clinton made an announcement about the discovery, at one point stating, “It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered."
The finding was not confirmed, however—there were simpler, inorganic explanations for the tantalizing patterns found in the Martian rock. So the search for signs of extraterrestrial life continued elsewhere.
However, the notion that germs can thrive deep inside a rock, even cold Antarctic rocks, is no longer surprising. Highly adapted microorganisms called endoliths have been found inside rocks two miles underground. They have also been discovered in deserts, in Antarctic permafrost, and in the Rocky Mountains, among other places. Some endoliths thrive in cracks and fissures, others in the cavities of porous rock, and several species actually burrow into the solid rock, leaving microscopic tunnels behind them. They apparently eat iron, sulphur or potassium, but some endoliths are capable of photosynthesis, as plants are. These tiny, simple organisms seem to be a good bet, perhaps the best bet at the moment, to show up as an extraterrestrial life form.
An endolith is an example of an extremophile, a microorganism that can survive and reproduce in conditions of severe temperature, acidity, alkalinity, or chemical concentration. Extremophiles are the basis for an important tenet of the exobiological faith tradition. If organisms can thrive in extreme environments on Earth, why not on other planets, or even comets and asteroids?
This leap of faith is further assisted by statistical assumptions about the probability of life evolving on other worlds. Of those currently estimated 8.8 billion “class M planets”, surely one of them must contain life, even intelligent life! And the third sign eagerly sought in the perennially quiet heavens is liquid water, now apparently flowing almost everywhere in the known universe. These three stigmata—extremophile biology, statistical probability, and running water—comprise the foundation of exobiological orthodox belief.
But wait, aren’t germs bad, especially extraterrestrial germs, for which we have no native immunity? A number of science fiction and horror movies over the years have ruminated on this fear. The Andromeda Strain (1971) is probably the best known, an extremely tedious film where scientists fretted about the end of the world while sitting at their desks. Other films include the 1978 remake of Invasion of the Body Snatchers, and the beloved Stephen King vignette "The Lonesome Death of Jordy Verrill" in Creepshow (1982). Arguably The Blob (1958) and any of its reincarnations depict infection by a voracious amoebic macroorganism from outer space.
I recently participated in a spirited discussion about the possibility of life on other planets in one of the on line communities I frequent. Nearly everyone agreed that extraterrestrial life would take the form of some type of microbe, possibly a dangerous one. Even though some members imagined such organisms as a source of new medicines to combat human diseases or being useful to industry, most were anxious about infection and planet-wide epidemics. One contributor predicted that encountering alien pathogens would be a boon to the disinfectant industry.
In the 1979 book Diseases from Space, Fred Hoyle, and N.C. Wickramasinghe claimed that illnesses like the flu, whooping cough and even the common cold were extraterrestrial in origin. Hoyle, a noted and controversial astronomer and science fiction writer, was a proponent of panspermia, the theory that life did not originate on earth but was carried here by comets, meteorites and other cosmic debris.
Hoyle and his colleague Wickramasinghe used spectroscopic analysis of stellar gas clouds to argue that they were composed of desiccated bacteria. They also believed that genetic material in the form of various pathogens falling from space contributed to genetic modification in terrestrial organisms over time, that is, to evolution on Earth. ‘More research is needed,’ as is often said, but the idea remains fascinating.
(A more recent dramatization of this notion is in the opening scene of the 2012 film Prometheus, where the origin of life on earth is explained as the result of the death and dissolution of a visiting extraterrestrial humanoid.)
Alas, not a shred of evidence currently exists for life anywhere else in the cosmos than on Earth, which may be a blessing depending on your perspective. Not even the exhalations of microbes have been detected by our Martian probes. In the absence of any facts that might contradict our speculations, we are free to project our most hopeful and our most dire visions on the blank lifeless canvas of space. On that dark surface we are likely to depict the aspirations and anxieties we have here on earth.
Readers may have come across the essay by Seth Shostak in last Sunday’s New York Times, (“Should We Keep a Low Profile in Space”). Shostak is the director of the Center for SETI Research, SETI being the famed project devoted to listening to outer space for alien communication signals. After about fifty years, nothing has been heard, so some are proposing that the Earth send out its own signal and await a response, a sort of multi-media e-mail blast to the heavens. We should speak to the void, not merely listen to it.
Not everyone agrees. According to Shostak, the renowned physicist Stephen Hawking worries that drawing the attention of a superior alien civilization will recapitulate the historic fate of indigenous peoples on earth, who, being less technologically advanced than their “discoverers”, were soon vanquished. Popular science fiction tends to assume that extraterrestrial civilizations are much like ours: aggressive, greedy, arrogant, and rapacious—a projection into space of our less attractive characteristics as a species.
But some signals have already been sent: a Beatles song has been sent towards the North Star, and a Doritos commercial was sent to a planetary system in the Big Dipper constellation. My hunch is that the Doritos message is most likely to get a response, though the Beatles have universal appeal. Shostak says that some of his colleagues have proposed transmitting the contents of the Internet into outer space. Given the multifarious and often unsavory contents of the web, doing this may be perceived by extraterrestrials as an act of war.
It is interesting, to me at least, that extraterrestrial life is often assumed to be highly intelligent, technologically advanced, and evil. Whether microbial, or something a bit larger and more complex, isn’t it just as likely that extraterrestrial life will be stupid, slow and, well, edible? Maybe our first words to an alien life form will not be “We come in peace—we extend the hand of friendship,” or some such. Maybe those first words will be “Hmmm, tastes like chicken.”
Since around the 1960s we have apparently lowered our expectations of extraterrestrial life from humanoid conquerors and bug-eyed monsters—desirous of human females to repopulate their dying planet—to mere microbes. But even the latter have not yet been found anywhere but on the Earth. Perhaps we should give the search a bit more time and effort. Can it be that our greatest fear is simply that we are alone among all these stars, that we are special because of our awesome solitude, that our tiny microbe of a world is in fact unique and miraculous?