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We are now tantalizingly close to getting that look. UC Berkeley researchers have built a Mars life-detection chip they believe is up to a million times more sensitive than Viking's instruments. Researchers at Cal and NASA Ames who study life in extreme environments have provided a game plan for where to look for life in our solar system. And the Bay Area's famed planet-hunting team led by Cal astronomer Geoff Marcy has trained its telescopes on nearby stars and found increasing evidence that small, rocky planets like ours are common. The team recently announced that it had even found a planet with water, the number one prerequisite for life as we know it.
Yet despite the field's banner decade, NASA's recent and highly controversial U-turn in mission priorities, which emphasizes a return to the moon instead of exploring deeper space, has sucked the wind from astrobiology's sails. NASA funding for its astrobiology program was cut in half this year, with no prospect of reinstatement any time soon. At the same time, several long-anticipated space missions to seek evidence of life in our solar system, and habitable planets outside of it, have been scrapped. It's an agonizing time for some of the field's top researchers. They've come so close to finding answers, yet remain so far.
The Case for Mars NASA's plan to return to the moon went over like a lead brick with astrobiologists, many of whom deride it as having little scientific value we've already got plenty of moon rocks. The agency's next priority, a manned expedition to Mars, has a few more supporters, among them Chris McKay.
His top three reasons we might find life on Mars: It used to have liquid water, it has the chemicals necessary for life, and its cold, dry, low-pressure atmosphere is essentially a giant freezer vacuum that would have preserved samples nicely. "I really want to find aliens," he says, "even if they are little, green, microscopic, and dead."
That may well be the best-case scenario for Mars. If life started there, it didn't evolve very far. Anything still living would likely be buried in the polar permafrost or deep under the surface, where it's protected from the arid climate and surface radiation. More likely, McKay says, it's long dead. But that's okay, since death proves life: Dead tissue is different than organic matter that never lived. Better yet, it leaves behind evidence.
That's why McKay found himself in Chile's Atacama Desert with UC Berkeley chemist Richard Mathies two summers ago. Mathies has designed a life-detection chip he believes can pick up where Viking left off, even if Mars is pretty much a ghost planet.
The Atacama is the driest, and therefore most Martian, place on Earth. It gets one millimeter of rain a year, and even that, Mathies says, is "one night when the fog came in." It is so dry that McKay once thought his instruments were broken because they hadn't recorded any moisture in two years.
The aridity, and the soil's chemical reactivity, which is similar to that observed by Viking on Mars, makes the Atacama incredibly popular with astrobio types wanting to test-drive prototypes. If your equipment can't find life in the Atacama, good luck finding it anywhere.
To get there, Mathies says, you drive toward the Andes until the terrain completely drains of life. "There's no twigs, no little bugs, no ants crawling, nothing," he says. "It's just nothing." Any microbial life that's managed to survive there is hiding out in the soil, beneath a gypsum crust that has likely not been disturbed in a hundred thousand years. Hack into it, and see if anyone's home.
The hacking is important Mathies believes one of the flaws of the Viking landers, as well as the Mars Rovers that were able to churn up a few centimeters of soil by grinding their wheels, was that they looked only near the surface. His chip, the Mars Organic Analyzer, is scheduled to fly on the 2013 ExoMars mission sponsored by the European Space Agency. The mission should be able to drill two meters below the Martian surface, a depth at which Mathies believes life would have been sheltered from the climate and radiation. His 2005 trip to the Atacama showed that although surface life was barely detectable, it was another story once they dug under the crust. "Go to a shielded environment, bam!" he says. "You get a whole bunch more."
Mathies' microfluidic chip is a thing of beauty, a transparent glass and plastic disc ten centimeters across, woven with a delicate labyrinth of channels. Soil samples are propelled through the channels using a system of water and tiny pneumatic pumps and valves. A linked-in computer analyzes the samples and would transmit results back to Earth.
But how, exactly, will Mathies know if he's found alien life, especially if it's really bizarre? And what is life, anyway?
You'd think there'd be a concise, universally accepted answer to the latter question, but there isn't. After all, we've only seen one sprawling example of life. Even though Earth is teeming, its organisms are all thought to be descended from the same source, all part of the same tree of life. At best, astrobiologists usually agree on some working guidelines that life reproduces, consumes energy, and evolves but even these criteria, they point out, describe what life does, not what it is.
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