Snot-tites!

What are these globs of slime oozing in a cave? Stalactites, rock formations that hang from cave ceilings like icicles? Guess again. They're "snot-tites" (that's what scientist dub them)--living formations of bacteria.

The microbes may be unique to a cave called the Cueva de Villa Luz in southern Mexico. Poisonous hydrogen sulfide fumes infiltrate the cave, possibly from a nearby oil field or volcano.

Donning breathing masks for protection against the fumes, a team of scientists trudged through mud and waist-high water deep inside the cave. There they stumbled on a dark, damp world teeming with life--bats, spiders, fish, crickets, and the bizarre microbial goo.

The life forms in Villa Luz haven't only adapted to the sulfur--they depend on it for survival. The cave's fish and insects devour the snottites, which derive energy from sulfur (much like common plants using sunlight for fuel).

Snot-tites may be living proof of a relatively new theory on how some caves formed. Most caves form when carbonic acid (rainwater mixed with carbon dioxide) dissolves limestone and carves hollow spaces in rock. In the case of Villa Luz, snot-tites drip sulfuric acid, a much stronger rock eater than carbonic acid.

"What we're seeing is a process where life is generating an acid that eats through the rock and helps to form this cave," says Louise Hose, a speleologist (cave scientist) who led the expedition. "What we see here is life creating a habitat for itself!"