Scientists and engineers at UC San Diego and UC Berkeley are developing a pocket-sized instrument that will travel to Mars aboard a European spacecraft and prove whether life exists -- or ever did -- on the planet's red sands.

The mission's instrument will mark the most sophisticated effort yet to find specialized organic chemicals that only exist in living organisms and never anywhere else in the solar system, the scientists say.

The instrument, so small it can fit in the palm of a hand, will fly on the European Space Agency's ExoMars spacecraft that will land in the planet's frosty north polar region, drill 6 feet below the surface and dig up tiny samples of dirt for analysis. The mission is to be launched in 2013.

"And if there's life there, we'll detect it," said Jeffrey Bada, a chemistry professor at UC San Diego's Scripps Institution of Oceanography in San Diego. "We've been working on this for 15 years, and it will be so sensitive that we should detect chemicals in parts per billion -- amino acids in a single bacterium, if there are any."

The UC instrument is being developed for NASA. It is called the Urey Mars Organic and Oxygen Detector and is named for the late Harold Urey, a famed physical chemist whose graduate student, Stanley Miller, in 1953 devised the first experiment that turned simple inorganic chemicals into amino acids, the so-called "building blocks of life."

Bada is the leader of the development team and his principal colleague is Richard Mathies, a UC Berkeley chemistry professor.

The scientists in the Urey experiment don't necessarily expect to find living Martian bacteria, but they do hope to detect the amino acids that are a key ingredient of life.

The molecules of amino acids have a twisted shape -- something like a corkscrew -- and they come in left- or right-handed forms, known as chirality. Nonliving organic compounds have mixtures of both forms, but in living organisms a single type of "handedness" -- either left or right -- dominates in each amino acid.

On Earth, left-handed amino acids dominate in all living things, but in life on Mars the amino acids might go either way, Bada said. Their property will be the definitive clue revealing whether Martian life is real, either now or in the past, he said.

Scientists at the NASA Ames Research Center in Mountain View, at NASA's Jet Propulsion Laboratory in Pasadena, and at the Leiden Institute of Chemistry in the Netherlands are also involved in developing the Urey experiment's components.

This will be only the second trip to Mars with the explicit mission to search for life.

NASA's two Viking spacecraft landed there 30 years ago and carried miniature laboratories to search hard for signs of life, but technology built into those instruments was not advanced enough to do anything but reveal some exotic chemistry.

The two robot rovers still scouting the Martian surface three years after they landed have found plenty of evidence that water once filled lakes and seas on the planet, but they aren't seeking life. And although the orbiting Mars Reconnaissance Observer has detected water that may still be running from underground streams onto the surface, it is not equipped to analyze chemical compounds on the surface.