Looking for life in peculiar places

Princeton geoscientist part of team seeking signs deep within other planets

By Steven Schultz

Princeton NJ -- After 10 years of burrowing deeper and deeper into the Earth in search of life in odd places, Princeton geoscientist Tullis Onstott is taking an opportunity to look up.

Tullis Onstott

Tullis Onstott, professor of geosciences, collects samples of rock and water from deep gold mines of South Africa and analyzes them in the laboratory for signs of life. NASA is interested in expanding his approach for use on Mars.


Onstott is part of a multi-institutional team that recently won a major NASA grant to devise methods for identifying signs of life deep within other planets. The consortium, called the Indiana-Princeton-Tennessee Astrobiology Institute, will receive $5 million over five years with a goal of developing instruments that could extract evidence of alien microbes, or even the organisms themselves, from underneath the surface of Mars.

"What we're trying to do is build a program that would take us to Mars within the next 15 years," said Onstott.

The National Aeronautics and Space Administration chose the Indiana-Princeton-Tennessee team in part because of Onstott's expertise working at the intersection of microbiology and geology. Since 1994, he has been leading a hunt for microbes in gold mines of South Africa, extracting previously unimagined organisms from searing hot, radiation-bathed rock two miles beneath the Earth's surface. Before that, he pulled exotic organisms from American natural gas reservoirs. As part of the new Mars effort, he is beginning a project to look for organisms in the icy gold mines in Northern Canada.

"It's amazing where miners go to get gold," Onstott said. "It's 'extreme mining.'" The same could be said of Onstott's science. He and members of his lab regularly descend into these mines and, amid the grime, din and stifling heat, collect uncontaminated samples of rock and water that they carry to the surface for detailed laboratory analysis. Their efforts have paid off with the discovery of extraordinary organisms that are completely isolated from the sun and the normal surface ecosystems and yet eke out a living in the deep rock. For energy, these bugs consume hydrogen gas that gets split from water by radioactivity.

The Indiana-Princeton-Tennessee team, which is led by geochemist Lisa Pratt of Indiana University, was among 12 groups that received funding and the designation as a "lead team" in NASA's Astrobiology Institute after a competition that started with 38 groups. The lead teams represent a wide range of research under the general subject of astrobiology, from understanding the formation of habitable planets to investigating the origin, evolution and biology of life on Earth. The Indiana-Princeton-Tennessee team has the potential to contribute to many of those areas, according to Rosalind Grymes, deputy director of the NASA Astrobiology Institute.

"They are looking at every aspect -- the geology, chemistry, physics and biology -- of subsurface life and understanding the whole suite and interplay between these areas," said Grymes. By demonstrating how organisms can live while sequestered from the planet's surface, Onstott already has helped expand the search for extraterrestrial life to a much wider range of possible habitats than were previously considered, she said.

Radical thinking

According to Pratt, the principal investigator of the team, Onstott "is the one who five or six years ago believed so strongly in what at that time was considered pretty radical thinking about the diversity and importance of deep-Earth microbiology. He had the conviction to seek major funding when I think, by and large, this was viewed as a long shot. Now, of course, it's becoming increasingly accepted and part of our way of thinking about microbes on Earth."

Onstott and Pratt, who shared an office as graduate students at Princeton, began collaborating a year ago to build a team of researchers with the broad expertise necessary to turn this foundation into a search for extraterrestrial life. Other researchers participating in the team are from the University of Tennessee, the University of Toronto, the Pacific Northwest National Lab, Lawrence Berkeley National Lab, Oak Ridge National Lab and the Lunar Planetary Institute. At Princeton, geoscientist Satish Myneni and chemists Gerard Dismukes and Edward Stiefel also will participate.

Onstott said the group's research will proceed along two main paths. First they will expand the work he started in deep gold mines to identify chemical and biological clues that organisms have left in the rock or briny permafrost. Then they will devise tests to recognize these "biomarkers" and distinguish them from anomalies that may have resulted from natural processes other than life. These tests need to anticipate the possibility of life forms that are very different from those found on Earth, including ones that are not based on nucleic acids, the material of DNA, Onstott said.

Ultimately, these tests need to be refined and engineered so they "could be strapped onto a drill and sent to Mars," Onstott said. The next Mars mission with the possibility of carrying such an experiment is scheduled to launch at the end of this decade, said Grymes.


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