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Friday, November 15, 2013

Reading List: First Contact

Kaufman, Marc. First Contact. New York: Simon & Schuster, 2011. ISBN 978-1-4391-0901-4.
How many fields of science can you think of which study something for which there is no generally accepted experimental evidence whatsoever? Such areas of inquiry certainly exist: string theory and quantum gravity come immediately to mind, but those are research programs motivated by self-evident shortcomings in the theoretical foundations of physics which become apparent when our current understanding is extrapolated to very high energies. Astrobiology, the study of life in the cosmos, has, to date, only one exemplar to investigate: life on Earth. For despite the enormous diversity of terrestrial life, it shares a common genetic code and molecular machinery, and appears to be descended from a common ancestral organism.

And yet in the last few decades astrobiology has been a field which, although having not so far unambiguously identified extraterrestrial life, has learned a great deal about life on Earth, the nature of life, possible paths for the origin of life on Earth and elsewhere, and the habitats in the universe where life might be found. This book, by a veteran Washington Post science reporter, visits the astrobiologists in their native habitats, ranging from deep mines in South Africa, where organisms separated from the surface biosphere for millions of years have been identified; Antarctica, whose ice hosts microbes the likes of which might flourish on the icy bodies of the outer solar system; to planet hunters patiently observing stars from the ground and space to discover worlds orbiting distant stars.

It is amazing how much we have learned in such a short time. When I was a kid, many imagined that Venus's clouds shrouded a world of steamy jungles, and that Mars had plants which changed colour with the seasons. No planet of another star had been detected, and respectable astronomers argued that the solar system might have been formed by a freak close approach between two stars and that planets might be extremely rare. The genetic code of life had not been decoded, and an entire domain of Earthly life, bearing important clues for life's origin, was unknown and unsuspected. This book describes the discoveries which have filled in the blanks over the last few decades, painting a picture of a galaxy in which planets abound, many in the “habitable zone” of their stars. Life on Earth has been found to have colonised habitats previously considered as inhospitable to life as other worlds: absence of oxygen, no sunlight, temperatures near freezing or above the boiling point of water, extreme acidity or alkalinity: life finds a way.

We may have already discovered extraterrestrial life. The author meets the thoroughly respectable scientists who operated the life detection experiments of the Viking Mars landers in the 1970s, sought microfossils of organisms in a meteorite from Mars found in Antarctica, and searched for evidence of life in carbonaceous meteorites. Each believes the results of their work is evidence of life beyond Earth, but the standard of evidence required for such an extraordinary claim has not been met in the opinion of most investigators.

While most astrobiologists seek evidence of simple life forms (which exclusively inhabited Earth for most of its history), the Search for Extraterrestrial Intelligence (SETI) jumps to the other end of evolution and seeks interstellar communications from other technological civilisations. While initial searches were extremely limited in the assumptions about signals they might detect, progress in computing has drastically increased the scope of these investigations. In addition, other channels of communication, such as very short optical pulses, are now being explored. While no signals have been detected in 50 years of off and on searching, only a minuscule fraction of the search space has been explored, and it may be that in retrospect we'll realise that we've had evidence of interstellar signals in our databases for years in the form of transient pulses not recognised because we were looking for narrowband continuous beacons.

Discovery of life beyond the Earth, whether humble microbes on other bodies of the solar system or an extraterrestrial civilisation millions of years older than our own spamming the galaxy with its ETwitter feed, would arguably be the most significant discovery in the history of science. If we have only one example of life in the universe, its origin may have been a forbiddingly improbable fluke which happened only once in our galaxy or in the entire universe. But if there are two independent examples of the origin of life (note that if we find life on Mars, it is crucial to determine whether it shares a common origin with terrestrial life: since meteors exchange material between the planets, it's possible Earth life originated on Mars or vice versa), then there is every reason to believe life is as common in the cosmos as we are now finding planets to be. Perhaps in the next few decades we will discover the universe to be filled with wondrous creatures awaiting our discovery. Or maybe not—we may be alone in the universe, in which case it is our destiny to bring it to life.

Posted at November 15, 2013 23:24