Pittsburgh team leader Nathalie Cabrol, who radiates the toughness of an expedition climber, would seem to be their human counterpart. When the Zo mission ends in mid-October, she will say goodbye to the Holiday Inn, and, again under the aegis of NASA, make her fourth ascent of the 19,731-foot Lincancabur volcano on the eastern side of the Atacama. "I´m not a daredevil," she tells me in accented English, "but I am free-diving in lakes at 20,000 feet, so you understand where I am coming from." At an altitude that would tax most people´s ability to stay upright, she intends to dive into a crater lake near the summit to measure with various instruments the lengths to which life will go to stick around."I´ve been around the block, the extreme block, a couple times, and I have yet to find a place where I didn´t find life," she says. "Everywhere you find a hurdle, you find a way life found to get around it."