November 20, 2009--Cave scientists Diana Northup and Jim Evatt sit near the entrance to Four Windows Cave in El Malpais National Monument, New Mexico, on January 10, 2004.

Since 1994 Northup, a geomicrobiologist at the University of New Mexico, and colleagues have been seeking out unusual deposits in caves and putting them under a microscope or testing them for DNA.

In October 2009, her team announced their discovery that some of the crystal-like deposits are actually mats of waste that have been excreted by previously unknown types of microbes. The work, presented at a meeting of the Geological Society of America in Portland, Oregon, could offer clues in the search for life on Mars and beyond. (Read the full story.)

"We're finding that you need to look at things you might write off as not being biological—they might be biological," said Penelope Boston, a cave scientist at the New Mexico Institute of Mining and Technology in Socorro who's worked with Northup on past projects.