These huge numbers suggest a great capacity for mutation and genetic variation. Let's visit a few of these frontiers to meet our fellow travelers. In South Africa, at more than 3 kilometers down into the Earth, researchers from Princeton University found a veritable zoo of types of microbes, some of which are in biofilms. At these depths, thermophilic and other microbes were found in rocks 2.9 billion years old. Evidence of microbial activity has been found in oceanic basalts by a team including Steve Giovannoni of Oregon State University.
Surveys suggest that bacteria have colonized much of the upper crust under the ocean.
Antarctica is another frontier yielding life in abundance. In the region there known as the Dry Valleys, lakes have permanent ice-covers. Tiny oases of life pit these ice blocks, which were carved from two meters down. In a far different environment, beneath the East Antarctic ice sheet, lies Lake Vostock, the largest sub-ice lake known to exist. This relief map of Antarctica's ice topography, derived from satellite data, shows the lake's location.