Astrobiologists gather at NASA

Conference examines origins of life on Earth, elsewhere in the universe, and the future

Apr 1, 2004
Ivan Oransky(ioransky@the-scientist.com)

MOUNTAIN VIEW, CALIF—If you want to know where you're going, it helps to know where you've been. Nowhere was that more true than at the third Astrobiology Science Conference, which began here on Sunday (March 28) and runs through Thursday at the NASA Ames Research Center.

The conference, which drew more than 700 participants, according to organizer Lynn Rothschild, a NASA Ames research scientist, focused on three questions: “Where do we come from?” “Are we alone?” and “Where are we going?” Previous efforts have focused on the first two questions, while giving short shrift to the third, Rothschild told The Scientist. “I think astrobiology has grown as a discipline,” she said. Last year, NASA issued a final version of its Astrobiology Roadmap.

The Mars expeditions may be the focus of much attention right now—and there was buzz here earlier in the week about data on “concretions” found by the Mars Rover that may or may not suggest the presence of fossils—but Earth is still the easiest place to figure out how life may have developed here and elsewhere. Indeed, the home planet took center stage—in fact, a 10-foot image of the Earth hovered behind the speaker's podium, next to smaller images of a galaxy and a familiar red neighbor planet. So a number of the talks and posters presented here looked an awful lot like traditional evolutionary, ecologic, and molecular biology.

For example, extinctions, both historic and predicted, were a common theme. “As enthusiastic as most of us are about science fiction, we don't really believe that we can have Jurassic Park,” said Stuart L. Pimm, professor of conservation ecology at Duke University, speaking on the effects of increasing rates of climate change on extinctions.

Others discussed how species originate and where they're going. For example, David Jablonski, of the University of Chicago, presented data on marine bivalve genera showing that taxa are not only generated, but accumulate, in the tropics. Jablonski said that models of the tropics as either “cradles” or “museums” portray a false dichotomy. “The tropics are truly the planetary engine of biodiversity,” Jablonski said, and are also responsible for exporting species to higher latitudes.

If species do live on other planets, they exist in conditions that most Earth species would find inhospitable. Posters focused on how species would have adapted to UV radiation, solar flares, and Mars polar conditions. Panelists discussed their study of extremophiles, including viruses, to understand how species might survive inhospitable environments.

David Alcantara-Diaz and colleagues of the Instituto Nacional de Investigaciones Nucleares, near Mexico City, found that Escherichia coli “followed different adaptive pathways even under the same selection agent”—strong UV radiation at levels simulating Mars. Some strains made use of well known nucleotide excision repair genes such as polA, while others showed mutations in radA. One UV-resistant strain showed 850 times the normal mutation in dnaE and dnaQ genes after exposure. The genotypic differences were all reflected in a phenotypic resistance, Alcantara-Diaz told The Scientist, but the mechanisms were distinct.

One way species may have ended up on other planets is contamination following space missions originating on Earth, a notion first put forward by Joshua Lederberg in the 1960s. But a poster presented by Andrew C. Schuerger of the Kennedy Space Center in Florida and colleagues suggested that at least one common contaminant of unmanned space missions, Bacillus subtilis, would not survive in large numbers, if at all, on Mars. The data followed on a previous study of the subject.

And Carlton Allen, NASA's astromaterials curator, addressed the risks of contaminating Earth with material returned from comets, the Moon, and Mars, saying that samples will be kept “strictly contained from the surface of Mars to biosafety labs on the Earth.” Allen noted that life on Earth has evolved in the presence of material from Mars in the form of meteorites, which he said were probably not heated high enough to sterilize them on their way to the Earth.

Understanding the past is also important for planning space exploration, said Steven Dick, NASA chief historian. He described early “evidence” of life on the Moon—seasonal patterns of light and dark and changing patterns of carbon dioxide—dating back to the 1920s and 1940s.

The lessons of the past were also hinted at by Annabel Ford, of the MesoAmerica Research Program at the University of California at Santa Barbara, who warned that the search for life elsewhere in the universe might be limited by a narrow view of what such life might look like. “When people hear 'astrobiology' they conjure images that are vaguely human,” said showing a slide of a scene from 'ET.'”