Saturday science subject: The Urey instrument

— 10:20 AM on May 3, 2008

Was there ever life on Mars? That's a question the European Space Agency hopes to answer through the ExoMars mission, which will fly to the red planet in 2013. As the New Scientist reports, one crucial element of the mission—the Urey instrument—has received $2 million in funding from NASA, and it will probe Martian soil two meters (6.6 feet) below the surface in order to seek out amino acids.

Chemical signs of life can be ambiguous, but scientists are hoping that Urey will be able to tell whether any amino acids on Mars were made by living organisms or some other process.

The key is to measure the symmetry, or "chirality" of each amino acid, which can be in either of two mirror-image configurations, labelled L and D. . . . "Life on Earth is based on chiral molecules, so our underlying assumption is that this is a central feature of biochemistry," says instrument team leader Jeffrey Bada of the University of California, San Diego, US.

The lesson from Earth is that biology will use only one of the two possible chiral forms. All amino acids in terrestrial life are of the L form, whereas synthetic amino acids come in equal mixtures of L and D.

In order to distinguish between L and D variants, Urey will see how the amino acids react to a chiral molecule dubbed g-cyclodextrin, the New Scientist says. Researchers behind the Urey instrument are counting on the device's very high sensitivity, which is high enough to detect "a few cells per gram," according to Bada.

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