Antarctic nitrous oxide provides key clue.

• Position: Life on Mars

In so many ways, Don Juan Pond in the Dry Valleys of Antarctica is one of the most unearthly places on the planet. An ankle-deep mirror between mountain peaks and rubbled moraine, the pond is an astonishing 18 times saltier than the Earth's oceans and virtually never freezes, even in temperatures below minus-40[degrees]F. A research team led by biogeochemists from the University of Georgia, Athens, has discovered at the site a previously unreported chemical mechanism for the production of nitrous oxide, an important greenhouse gas. Possibly even more important, the discovery could help space scientists understand the meaning of similar brine pools in a place whose ecosystem most closely resembles that of Don Juan Pond: Mars.

The research adds an intriguing new variable to growing evidence that there has been--and may still be--liquid on Mars, a usual prerequisite for the formation of life. In fact, the new findings could help researchers develop sensors for detecting such brines on Mars--thus narrowing the search for places where life may exist.

"The pond's soils and brines and the surrounding rock types are similar to those found on Mars," confirms Samantha Joye, a faculty member in the Department of Marine Sciences. "It provides an ideal location to assess microbial activity in extreme environments. While we did not detect any 'bio-gases' such as hydrogen sulfide and methane, we did, surprisingly, measure high concentrations of nitrous oxide, which normally is an indicator of microbial activity. We needed to find out whether a nonorganic process could account for this nitrous oxide production."

Scientists have been fascinated with Don Juan Pond since its discovery in 1961. (While the site is lovely, there is nothing romantic about the name, which comes from the helicopter pilots who fin found it, Don Roe and John Hickey.) From the time of its discovery, researchers realized they had found a place like nowhere else on Earth.

The pond--roughly a 1,000- by 400-meter basin--is the saltiest body of water on Earth by far, some eight times saltier than the Dead Sea. While researchers more than 30 years ago reported finding abundant and varied microflora of fungi, bacteria, bluegreen algae, and yeast, since then and during the Joye team's...