Will NASA ever find life on Mars?
Discovery of water ice hints that Red Planet could be home to microbes
 NASA / JPL /University of Arizona |
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The discovery last week of water ice just under the surface of Mars has researchers buzzing, given that water is a key ingredient for life. The finding, by the Phoenix Mars Lander, is the most recent hint that the Red Planet might be habitable to microbes.
But in the parlance of treasure hunters in the movie "National Treasure," this looks a lot like just another clue that will lead to other clues, and still more clues. The big question still hangs over NASA: Is there life on Mars? And just as important: Can NASA ever find the evidence for it?
Getting to that answer will require the right mission with the right tools in the right places — not to mention some serious digging beyond the capabilities of Phoenix. The next Mars missions include NASA's Mars Science Laboratory, an SUV-sized rover set to launch in 2009, and the European ExoMars rover that would wield a drill capable of digging 6.5 feet down. It is set to launch in 2013.
NASA has long taken an incremental approach to searching for biology, with "follow the water" as a driving strategy. That means, perhaps to the frustration of some, that the current Phoenix lander mission and the twin rovers on Mars are not even designed to detect Martian life.
So current and near-future missions may not directly look for life, scientists say, but they will likely turn up more pieces to the puzzle of Mars and where extraterrestrial life may thrive.
Location, location
Scientists generally agree that finding existing or previous life means digging down at least a meter, away from the harmful radiation on the surface of Mars.
The Phoenix lander has scraped away enough of the surface to uncover crumbs of water ice, but its backhoe-like robotic arm cannot reach down far enough to try and find whatever life may exist under the north polar region.
"Phoenix could easily be sitting a meter or two above pay dirt," said Michael Storrie-Lombardi, an astrobiologist who heads the Kinohi Institute in California.
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However, the melting and refreezing of water could also erase records of previous life or organic material, scientists say. That presents a dilemma between searching for existing life versus past life.
"We don't know exactly how fast the ice comes and goes," said Jack Farmer, an astrobiologist at Arizona State University. "If it's on a routine basis, then you may end up losing the biosignatures."
Farmer and other scientists may prefer a region that remains frozen year-round, preserving organic material and possible traces of past life in the ice.
That safer bet on finding evidence of past life — or at least preserved organic material — means going to places "that are fairly dry and act like a freeze-dried container," Storrie-Lombardi said.
But "if you really want to go for broke" and search for existing life, Storrie-Lombardi said, you need to dig in places where water may flow.
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Besides areas near the Martian north pole, scientists have also examined gullies where liquid water may have bubbled up recently in the planet's history. Finding an active hot spring could lead to finding life similar to extremophile bacteria that can thrive under intense conditions.
"Hot springs are at the top of my list," said Bruce Jakosky, a geologist at the University of Colorado who has worked on Mars missions. "Organisms might not survive and thrive on the surface, but recently exposed hot springs might bring something up from beneath."
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