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Scientist at Work: Lisa Pratt

Biogeochemist Lisa Pratt has slogged through arsenic-rich muds in southern Oregon, descended kilometers-deep, noxious gas-filled mine shafts in South Africa and Canada, and belly-crawled across salt pavements to sample brine pools in California's Carizo National Monument. What could possibly be next for the Indiana University Bloomington Provost's Professor of Geological Sciences who has spent much of her career seeking out microbes that live in places inhospitable -- even mortally dangerous -- to humans?

Lisa Pratt

Provost's Professor of Geological Sciences Lisa Pratt

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Though it may feel cathartic to say, "the stars" isn't quite right.

Pratt's research is indubitably Earth-bound, yet its purpose has always had at least a little bit to do with places far away. Very far away. The soils and ice caps of Mars. The deep, possibly water-filled depths of Jupiter's Europa and Saturn's Enceladus -- by studying the extremes life can tolerate on our own planet, we may be learning about the limits of life elsewhere.

"It's the most compelling question today," Pratt says. "Are we alone?"

To know the answer, humans must first trawl Mars for signs of life. The Spirit and Opportunity missions were successful, however success is measured. The two rovers provided humans with the most direct information yet about Martian geology and atmosphere, and elicited intense interest from the general public, many of whom sat riveted as they flipped through high resolution images of the Red Planet on their computer screens.

Mars may turn out to be a dead planet, harboring no evidence that life ever existed there. But we have only just begun to look, Pratt says. Spirit and Opportunity were just the beginning. Many new rover missions are in the works, all of which have the potential to stun us with fresh evidence of past or present life on Mars.

"I used to think this was just the stuff of daydreams," she says. "Now that I'm heavily involved, I have real hope that this is something I'll see before the end of my research career." (Which is many, many years away.)

From 2003 to 2008, Pratt was the leader of the $5-million NASA-funded Indiana-Princeton-Tennessee Astrobiology Institute, a project that studied energy and nutrient cycles that sustain life in the deep subsurface of Earth and, potentially, Mars. One of the fruits of that project was the discovery of bacteria on Earth that live kilometers below ground, in solid rock, and use the byproducts of irradiated water as a source of energy.

And she is the principal investigator of a new three-year, $2.4 million NASA grant to study microbial life at the edge of Greenland's receding ice sheet. She and her colleagues hope that by identifying patterns of methane production there will provide crucial context for analyzing methane plumes on Mars. As the hypothesis goes, if microorganisms leave an identifiable signature within methane plumes on Earth, then the identification of similar signatures within Martian methane plumes would be tantalizing indeed.

By virtue of these projects and others, and her participation in conferences and meetings of scientists and policymakers, Pratt has become an authority in the field of astrobiology, the study of the life that may exist beyond Earth's atmosphere. Because of her work, and that of many Bloomington campus colleagues -- environmental scientist Jeffrey White, who is a co-PI on the methane project, atmospheric scientist Sara Pryor, biochemist Carl Bauer, mineralogist David Bish, Stable Isotope Research Facility Director Ed Ripley, and others -- it can be fairly said IU is a force within the astrobiology community.

"IU is clearly identified now as a leader in NASA mission work," she says.

Most of that mission work can be described as helping future Mars rovers be more effective data gatherers.

"Mars is top priority right now because it's the easiest to get to," Pratt says. "We need to do a few things to make these missions more effective, however. We have to find a way to get deeper into the Martian subsurface. The surface is highly oxidized by Mars' atmosphere, which contains aggressive radicals. The surface also contains quite a bit of perchlorate, which 'scrubs' the surface of potential organic fossils. We need to get below this oxidized patina. We also need to find a way to drill into thick, dusty ice at the Martian polar caps to get to the layers that might tell us something about climate and climate change in the past."

Knowing how to look for life is one issue scientists are grappling with. Another is how to prevent Earth's own unique biological and non-biological materials from confounding studies or, worse, harming incipient life.

Greenland ice sheet

Photo by Bruce Douglas

A better understanding of methane release near the western edge of Greenland's mammoth ice sheet could help NASA look for life on Mars.

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"Contamination is a big deal," Pratt says. "Scientists and engineers are working together to figure out how we can study Mars, even bring samples back to Earth, without causing any more harm."

More harm -- because the people behind the Mars probe-landing Viking mission had not considered such things.

"Beyond Mars, there are many interesting places to explore," Pratt says. "My personal preference is (the Saturn moon) Enceladus. It has explosive plumes that we can fly a probe through without even landing it, which mostly takes care of the contamination issue. It is also believed there may be liquid water insulated below the moon's thick ice shell."

That's similar to Jupiter's moon Europa -- but Europa lacks the plumes, which so conveniently eject material for orbiting probes to capture.

Will that probe be adorned by an American flag and the NASA logo? Only if public support for exploration remains high.

"Relative to a typical federal budget these days, rover projects don't cost that much money," Pratt says. "But if we don't do it, I'm confident another space agency will. Perhaps the European Space Agency. Perhaps the Chinese or the Koreans. I admit I'm a little biased, but I prefer the way NASA does things -- they fuse science and engineering elegantly. They don't just put things up in the air. They make sure every project, every mission has a science-driven mandate."

This is an original article, published May 17, 2011.