Detecting Life

When scientists wanted to test the robot destined to explore Mars, they took it to the driest, most lifeless place they could find, the Atacama Desert. They hoped that the austere desert could help solve a mystery and prevent a blunder.

Even before H. G. Wells wrote his terrifying War of the Worlds, scientists wondered if life had ever existed on Mars. They finally sent a Viking lander mission with instruments to analyze the soil in hopes of stirring up some biochemistry in their testing. What they found was a bizarre and unexpected chemical reaction, but they could not determine whether the reactions they recorded were caused by the last, faint traces of life in the Martian soil. So scientists resolved to build a more sensitive detector and try to solve the mystery of the odd chemistry of the Martian soil. The recent robotic rovers sent to Mars did find clear evidence that Mars once had liquid water, including floods, perhaps rivers and either small oceans or large lakes. However, the roving robots did not have instruments sensitive enough to determine whether Mars ever evolved at least microscopic organisms that left behind traces in the amino acids that living molecules manufacture.

So a team from the University of California at Berkeley designed instruments for a new Martian rover that could detect even the faintest trace of molecules associated with living cells. Then they sent the rover and its instrument package straight to the Atacama Desert, to search for life in a place where it had not rained in years and where the soil had no visible trace of topsoil, plants, or organic debris. Not only was the Atacama soil seemingly lifeless, it had the same red tint and some of the same unusual chemical properties as the Martian soils. If the instruments checked out there, they could fly on a 0 European space mission. The instruments did find microscopic traces of amino acids in the desert soil, although at concentrations hundreds or thousands of times less than more temperate areas. The instruments even detected differences in the structures of the amino acids that proved conclusively they had been manufactured by living things. The scientists discovered they could safely redesign the instrument to make it even more sensitive, so that it can detect a trace of life ,000 times more faint than the landers could pinpoint in the 1970s.