Visions of Life on Mars in Earth’s Depths as Investigated by Princeton GEO team

WITWATERSRAND BASIN, South Africa — A mile down in an unused mine tunnel, scientists guided by helmet lamps trudged through darkness and the muck of a flooded, uneven floor.  Leaning a ladder against the hard rock wall, Tullis C. Onstott, a geosciences professor at Princeton, climbed to open an old valve about a dozen feet up. Out flowed water chock-full of microbes, organisms flourishing from heat generated from the interior of the planet below.

Discover Interview: Tullis Onstott Went 2 Miles Down & Found Microbes That Live on Radiation

The first time Tullis Onstott ventured underground, he squeezed into an elevator with dozens of South African gold miners and descended a mile into a pit called Mponeng. His goal: Finding the bizarre, hardy microbes that survive in sweltering, inhospitable rock. A geologist by training, Onstott spent his early career studying the Earth’s crust—until he heard a talk in 1993 about colonies of bacteria living thousands of feet below the surface. Ever since, he has made dozens of deep expeditions, sometimes paying his own way, and discovered bacteria living more than two miles beneath the surface in 140-degree-Fahrenheit heat. By investigating microbes in these harsh environments, Onstott is gleaning clues about how life could have begun in Earth’s hot, chaotic early days—and about what it might look like on other worlds. Even his office is underground, in the basement of Princeton University’s geology building, where Onstott met with DISCOVER reporter Valerie Ross.