“It is dangerous to assume life is common across the Universe.” These were the words of Charles Cockell at a Royal Society event on March 11 this year. While many people have freely debated the existence of extraterrestrial life, Cockell’s words carry a bit more weight than most. He happens to be the director of the U.K. Center for Astrobiology, based at the University of Edinburgh.
Bringing to mind the argument made by Fermi’s paradox — if the universe is teeming with life, where exactly is everyone? — this may seem at first to be a slightly pessimistic outlook. Evidently, however, the intention is not so much to pour cold water on the astrobiology research community, but to call into question our assumptions in the search for life elsewhere.
As Cockell went on to explain, ”People are encouraged to think that not finding signs of life is a ‘failure’ when in fact it would tell us a lot about the origins of life.”
In fact, this one single statement sums up what is potentially the biggest problem in astrobiology. We, quite simply, have no idea how life started. We don’t know where, how, when, or why molecules managed to replicate themselves into ever-more-complex forms and, eventually, living organisms.
Earth is the only example of a living planet that we have in the entire universe, and we don’t even understand it. Even now, biologists can still argue over what really constitutes a living thing, highlighted a couple of years ago by the discovery of giant viruses with genomes larger than some bacteria. And even if we did fully understand life here, there’s nothing to say it would be the same elsewhere.
Purely because we know life can exist on a planet like ours, with liquid water and at an appropriate distance from our star, we’re forced to search for life in similar situations. Habitable “goldilocks” zones are the target of planet-hunting missions like Kepler. The hope is that if we can find another Earth, then we can find another place that might have life.
But what if life doesn’t want to play ball? In his statement, Cockell warned that simply finding such a planet may not be enough: “On our planet, carbon leaches into most habitat space and provides energy for microorganisms to live. There are only a few vacant habitats that may persist for any length of time on Earth, but we cannot assume that this is the case on other planets.”
more @ http://news.discovery.com/space/alien-life-exoplanets/is-earth-rarer-than-we-think-130322.htm