It’s your typical spelunking saga: You squirm through tunnels no wider than a watermelon in diameter, then rappel over the edge of a 200-foot cliff into a void so black you can’t even see your feet, let alone the bottom-assuming there is a bottom. If you survive that ordeal, you’ll still have to negotiate the slippery slope of the “Freakout Traverse” or the dreaded crevasse known as the “Great White Rift.” A subterranean tour through Lechuguilla Cave in New Mexico might also include other highlights and lowlights: “Misery Hole,” “Death Pit,” and the “Parallel Universe.”
Some explorers enjoy the thrill of probing an uncharted, underground wilderness. Others find solace in the quiet and darkness of America’s deepest cave, which extends more than 1,500 feet below the surface. Then there are those who come searching for life on Mars.
Life on Mars? Indeed, as scientists explore the Red Planet via the Mars Pathfinder and a series of subsequent NASA missions planned over the next decade, other researchers are studying the microbial lifeforms that inhabit this vast cave in Carlsbad Caverns National Park, evaluating the possibility of analogous creatures lurking beneath the Martian surface. This work has been supported by NASA’s exobiology program from a budget designated for the study of “terrestrial analogs” to other planets. “We’re reconsidering the subsurface environment on Mars partly because the subsurface on earth is turning out to be very rich,” says Penny Boston, a biologist and NASA consultant at Complex Systems Research in Boulder, Colo. In fact, scientists are finding microorganisms almost everywhere they look-near vents on the floor of the deep ocean, inside Antarctic rocks, and at oil- and gas-drilling sites, thousands of feet underground.
The basic premise of the analogy to life on Mars goes like this: Some three to four billion years ago, Mars was a warmer and wetter place owing, in part, to a thick atmosphere of carbon dioxide that heated the planet through the greenhouse effect. Eventually this carbon dioxide combined with water to form carbonic acid which, in turn, reacted with rocks on the surface to create carbonates such as limestone and dolomite. This process depleted the carbon dioxide in the atmosphere, leaving the surface frozen and inhospitable with no liquid water to be found anywhere. “Now we’re saying that if life couldn’t have survived on the surface, maybe it moved underground,” explains Christopher McKay, a planetary scientist at NASA’s Ames Laboratory who has accompanied Boston and others on several Lechuguilla expeditions.
The entrance pit to Lechuguilla cave was discovered in 1914. But it wasn’t until the 1950s that investigators began to suspect there might be a cavern somewhere beneath the pile of rubble on the bottom of this pit. Once the rubble wall was eventually broken through in 1986, intrepid spelunkers tunneled in and began to chart more than 90 miles of passages. The full extent of Lechuguilla is not yet known, but Dale Pate of the National Park Service in Carlsbad, N. Mex., is convinced that “there’s a lot more cave out there than we know about, possibly 1,000 or 2,000 miles worth.”
Some call it the most beautiful cave in the world, with brilliant colors, pristine pools, and spectacular mineral formations that resemble flowers, crystals, chandeliers, and coral. Although scientists can appreciate this splendor, they are drawn to the cave mainly because it is the perfect place to study a virtually uncontaminated underground environment. “We do our best to limit the impact because we don’t want to contaminate and destroy the thing we hope to study,” Boston explains. “We’re looking for exotic organisms that are easy to distinguish from contaminants brought in by humans. But if we’re not careful, these contaminants might outcompete indigenous organisms.”