Other perils
Back at the STScI meeting, other dangers to life in the universe were laid out. Not all stars are as hospitable as our Sun, astronomers said. And we've not yet found anything close to an Earth-like planet. While it seems likely that solar systems like ours will be found, no one is certain that planet formation proceeds elsewhere as it did here.
In fact, most stars are now thought to have formed in clusters, where violent interactions may snuff out planet development altogether, said John Bally, an astrophysicist at the University of Colorado.
Those planets that do develop must travel through a narrow band of space around their host star, a so-called habitable zone where the temperature is just right, if they are to foster life as we know it. Worlds outside these zones would have to rely on some sort of internal heat to support life.
James Kasting, a top expert on habitable zones from Pennsylvania State University, said a mere 5 percent difference in position for most hypothetical planets around nearby stars would cause their oceans to evaporate away.
And Kasting also points out that if we
Efforts to find life on Mars have proved that. Researchers still cling to the possibility that Mars may harbor life in its soil or rocks, but after three decades of exploring the planet from above and even at ground level, the question is still open.
Think like a Martian
Whether there are Martians or not, Nealson, the geobiologist says it's time to start thinking like one.
In his view, the meaning of "life" has to be pondered from a non-Earth-centric viewpoint if scientists are to have any hope of finding life elsewhere.
Nealson says human researchers are saddled with a "biological bias" that limits their collective ability to detect life to varieties they already understand. He argues that new methods need to be developed that would identify physical and chemical signatures of life, rather than attempting to directly examine biology.
One approach would be to look for chemical reactions occurring over a matter of days when, without some sort of life as a catalyst, "they wouldn't happen in a thousand years."
Another method -- viable only for planets we can travel too -- would involve looking at how the chemistry of a body of water or a layer of sediment changes with depth. Every example on Earth exhibits a common "stratification" chemistry, he said.
"If you build Captain Kirk's tricorder [a rather magical scanning device], all it has to do is measure the profiles," he said.
Nealson said no Mars mission prior to 2009 has the tools necessary to search for life in this way. He argues that the prospects on Mars beg for testing new methods of looking for life no matter what it looks like.
It will be at least a decade before planned space-based telescopes will have the ability to crudely examine the atmospheres of distant planets for clues to the sorts of reactions Nealson discussed.
Smarter than scum
There is a potential shortcut to all these efforts. If life is more advanced, it would be relatively easy to find. In fact, "If life is advanced, it's going to find you," Nealson said.
An interesting idea, and one the folks at the SETI Institute have thought a lot about.
Jill Tarter, director of the institute's Search for Extraterrestrial Intelligence, said the effort is a branch of astrobiology that seeks to take advantage of the deliberate actions of other intelligent life, which she defined as civilizations that possess advanced technology capable of communicating electronically across light-years of space.
If anyone is sending signals our way, Tarter and her colleagues hope to detect them with increasingly creative approaches, from chunks of time at various telescopes around the world to a
of inexpensive antennas that would do other radio astronomy while simultaneously searching full-time for alien signals.
For now, SETI surveys a mere dot of sky compared to the vast reaches of our galaxy.
Nonetheless, if SETI finds a repeatable signal -- a true non-natural communication that can be verified by multiple detections -- astrobiology's biggest question would be answered in a flash. But it would also raise an issue that not too many astrobiologists were thinking about.
As Tarter pointed out, civilization on Earth represents the lowest form of technological advancement by the SETI definition. We've only been able to communicate electronically for a few decades. If there is anyone else out there with technology, sheer odds suggest they've had it much, much longer than we have. To them, we might be viewed as the scum of the universe.
"We really are the dumbest folks in the galaxy," Tarter told her esteemed colleagues.
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