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The Genome Sequencer as an Alien Life Form Detector

What to do if you're looking for signs of life in an alien world, but those life forms aren't DNA based? A genome sequencer, of course.

That's what scientists at the recent Lunar and Planetary Science Conference, as well as a paper in press in Astrobiology, says, Science reports.

Alien life forms may not use DNA or RNA as building blocks, making robotic explorers incapable of recognizing such beings, even if it were standing right in front of them. But with a genome sequencer, even if the alien had a completely different biochemistry, a genome sequencer "could still see a signal," astrobiologist Sarah Stewart Johnsons says.

The method works because nucleic acids such as DNA, "are promiscuous," according to Science. Johnson's team used a cancer biology technique called the systematic evolution of ligands by exponential enrichment, or SELEX, which creates a huge library of aptamers, then incubates them with a specific target. Typically repeating SELEX three times, scientists filter out those aptamers that aren't specific to their target.

For their work, though, Johnson's team essentially turned it around so that their sensor would expose samples to random aptamers and gather information from each hit. The patterns are amplified and sequenced, resulting in a complex chemical pattern, or a fingerprint.

The fingerprint might not be as clear as DNA caught in a sequencer, but if exposed to an aptamer library, the complex molecule would bind with more sequences than a simple molecule, which could be an indication of a life form. "'It might not be as definitive as our DNA sequencer, but it could be, if not a biosignature, a really strong bioprint,'"Johnson says.