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?
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