Guardian Of The Galaxy

LISA PRATT WAS NEARLY 2 MILES BELOW GROUND IN A SOUTH African gold mine when the lights went off and the air stopped moving.

Power had cut out, along with the reassuring roar of the ventilating fans that regulate the mine’s methane and carbon monoxide levels. Pratt, then an Indiana University geology professor, was hunting for evidence of life-forms capable of surviving in extreme dark, salinity, and temperature. As miners began to pour from a crease in the rock above her and run for the exit, it was clear that humans weren’t on that list. “It was not a good moment,” she recalls of that day in 2001. “I honestly thought that might be the end of the line.”

Today, Pratt’s work in such environments has led her to a brightly lit office at NASA headquarters in Washington, D.C., as the agency’s planetary protection officer. In this sparse room with a laptop and a whiteboard, she still ponders a question she faced during her years of crawling, sliding, and rappelling into harsh places to collect extremophiles: “How do you look for signs of life without inadvertently bringing life with you?”