IMMERSED IN THE PAST: To venture below the surface of Pavilion Lake is to take a trip back in time to observe Earth's earliest life-forms.
Donnie Reid

There's only so much you can do searching for extraterrestrial life when you're Earthbound. One approach is to locate and study the best terrestrial examples of what might resemble conditions that could support life on another planet.

View Slide Show Exploration of the Lake

That is exactly why astrobiologists are getting so excited about Pavilion Lake in British Columbia, Canada. Pavilion's lake floor is scattered with living coral reef–like structures called microbialites that result from microbes and minerals interacting over thousands of years. Although Pavilion's microbialites are believed to date back 11,000 years, they uncannily resemble structures that flourished on Earth some 540 million years ago.

Freshwater microbialites can be found in a handful of other places on Earth, but the diversity of structures at Pavilion is what sets it apart. There you will find microbialites shaped like cauliflower florets or artichokes growing on flat stretches of the lake's floor as well as ones that form chimneys and fingerlike protrusions, which cling to steep trenches farther down.

The idea is simple: If scientists can recognize what early life on Earth looks like, their hunt for life elsewhere should be better informed—because odds are that if life exists or existed, say, on Mars, it would be of the primitive sort. Along those lines, the research team at Pavilion has employed two single-person submersibles to map the lake floor this year. They are also busy sampling the lake's components (its sediment, water, isotopes and DNA from microbialites themselves) to reveal the signature of microbialite life. Once uncovered, tests could be devised to determine on future missions to Mars and other planets if similar structures are present.

When NASA astrobiologist Chris McKay emerged from Pavilion's waters after his first dive there he said: "I think I just walked back in time." Take the time trip yourself with this slide show.

View Slide Show Exploration of the Lake