The Aliens Among Us (Maybe)

By Joel Achenbach
Sunday, July 29, 2007

If we encountered alien life, would we recognize it? I don't mean large, ambulatory, tentacle-snapping organisms with eyeballs on the ends of stalks. Those are always obvious. I'm talking about the low-key, chilled-out microscopic life-forms that might be lurking below the surface of Mars, or beneath the crust of one of Jupiter's jumbo moons, or in some such exotic, slightly scuzzy planetary environment where you'd definitely never find a Starbucks.

What are we looking for, exactly, when we search for alien life? What is life?

That's the cosmic question pondered in a new report from the National Research Council, "The Limits of Organic Life in Planetary Systems." For more than five years, a committee of scientists tried to imagine what life-as-we-don't-know-it might be like. The conclusion: Life may exist in forms completely unlike anything we see on Earth. We need to keep our minds open to the possible existence of Weird Life.

You're thinking: Yes, and he works down the street at the video store. But even if this seems a bit silly, it's a big question, and a practical one. Our space program spends billions of dollars trying to figure out where life might be hiding in the solar system. Where do we look? The new report says that, in addition to exploring Mars, we may want to take a closer look at Titan, the huge moon of Saturn where pools of liquid hydrocarbons might contain Weird Life; and Saturn's moon Enceladus, which has geysers of water ice and water vapor shooting through its crust.

Even more provocative is the hypothesis advanced by scientist and author Paul Davies, that there may have been a "second origin" of life on Earth -- or many origins. Weird Life, in fact, may exist right now, on Earth, in what Davies calls a "shadow biosphere." We just haven't figured out how to look for it.

"It could be under our noses, or even in our noses," Davies told me. "The world is teeming with microbes -- squillions and squillions of them. The vast majority of which haven't been characterized, much less had their genome sequenced. We don't know what they are. And some of those might be shadow life."

Michael Meyer, lead scientist for NASA's Mars program, agrees: "Our capabilities of looking in the microbial world are still pretty crude. We have marvelously sensitive techniques for finding what we've found before."

Time to take another look under the sofa cushions.

All life as we know it has emerged through Darwinian natural selection. Evolution isn't simply something that happens to life after life gets rolling. NASA's official definition of life is that it's a "self-sustained chemical system capable of undergoing Darwinian evolution." But in the future it may be possible, the new report says, to manipulate human life so that it evolves via Lamarckian, as opposed to Darwinian, processes.

Jean-Baptiste Lamarck was an 18th-century French naturalist and early proponent of the notion of evolution. He proposed the idea, now discredited, of the "inheritance of acquired characteristics," in which attributes and talents gained during one's life could be passed on to one's heirs. Maybe he was just ahead of his time: "Humankind will be able to perceive and solve problems in human biology," the new report reads, "without needing to select among random events, thus sparing the species the need to remove unavoidable genetic defects through the death of individuals."

Every biologist would love to find even a scrap of extraterrestrial (or weird) life, because right now we have only a single example of biochemistry. We don't know the "rules" of organic chemistry, says John Baross, a University of Washington biologist and the lead author of the report.

That said, it's very hard to imagine an organism that wouldn't take advantage of the unusual properties of carbon and water. Carbon is great for making complicated three-dimensional structures -- a protein, say, or a DNA molecule. When we study the universe through telescopes, we see the tell-tale spectroscopic signatures of carbon molecules everywhere. Our cosmos has a hankering to do carbon chemistry. All life on Earth is carbon-based.

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