What life looks like on Mars?

Natural History, Oct, 2003 by Erin M. Espelie

A week of tramping for miles underground and sleeping in limestone catacombs tunneled out by sulfuric acid is not everyone's idea of happy camping. But Dave E. Bunnell--photographer and cave aficionado--is not everyone. He was thrilled to be among a small party of cavers allowed to map an arm of Lechuguilla Cave in southern New Mexico, the deepest cave in the continental United States. A few days in, after dozens of "squeezes" and lengthy rope climbs, Bunnell and his team stumbled across the area of orange calcite growths in the photograph, measuring several feet across.

This stunning cave is populated by a spectacular array of microorganisms. For despite the lack of light and nutrients, bacteria have adapted to Lechuguilla, some by absorbing metals such as manganese and iron. A number of investigators, among them Leslie Melim of Western Illinois University in Macomb and Diana Northup of the University of New Mexico in Albuquerque, are studying how the bacteria can build up calcified assemblages in caves--adding to the decor.

Melim and Northup believe that bacteria may have helped form the icicle-like extensions, known as "pool fingers," which point downward in Bunnell's picture. "Our working model is that bacterial slime is replaced or coated by calcite," says Melim. Such work in "extreme" environments is helping redefine where biologists search for life or its remains: think extraterrestrial.

Since 1996, caver and photographer DAVE E. BUNNELL ("The Natural Moment," page 6) has been the editor of NSS News, the magazine of the National Speleological Society. His photograph of orange flowstone was made in the western branch of Lechuguilla Cave, near Carlsbad Caverns in New Mexico, during a mapping expedition at the site (see his Web site at www.goodearthgraphics.com/virtcave).