Discovery Could Unlock Clues to Early Mars Life

A bizarre community of microbes has been discovered inside rocks in Yellowstone National Park, thriving in pores filled with water so acidic it can dissolve steel nails.

The clusters, interwoven with flourishing green algae, comprise at least 40 new species of bacteria, according to Jeffrey Walker, a University of Colorado microbiologist.

He and his colleagues say the microbes’ fossil forms could provide powerful clues to the nature of early life on Earth and life that may have existed billions of years ago on Mars.

Mr. Walker is a graduate student in the laboratory of Norman Pace, a leader in the emerging field of “astrobiology,” whose scientists are seeking the most promising earthly models for life on other planets. Mr. Walker, Mr. Pace and John Spear, another scientist in Mr. Pace’s laboratory, reported on the new microbes Thursday in the journal Nature.

“Spear and I were examining some gray rocks that looked very much like sandstone in the park’s Norris Geyser Basin,” Mr. Walker said, “and when we broke them up, we saw this beautiful, vibrant band of green inside.

“It turned out that the extremely acidic water in the pores of the rocks held networks of algae and bacteria, and the organisms we identified were varied species of mycobacteria.”

Aside from discovering the microbes and noting their extraordinary ability to live in the highly acidic water-filled pores, Mr. Walker said in an interview that he also found clusters of bacteria already encrusted with silica and other minerals – micro- organisms in the early stages of becoming fossils that will one day bear evidence of what they were like when they were alive.

Therein, the scientists said, lies the major significance of the discovery: the potential of the microbes to become fossils and serve as “biosignatures” for researchers seeking signs of early life in the remnants of ancient volcanism and hydrothermal activity on Earth – and, particularly, on Mars.

“The prevalence of this type of microbial life in Yellowstone means that Martian rocks associated with former hydrothermal systems may be the best hope for finding evidence of past life there,” Mr. Walker said.