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SETI Institute –

Chyba to deliver Bunyan Lecture on search for life in outer space

Are we alone? Stanford Professor Christopher Chyba, who also holds the Carl Sagan Chair for the Study of Life in the Universe at the SETI Institute in Mountain View, Calif., will explore that topic at 7:30 p.m. Monday, April 21, in Braun Auditorium of the Mudd Chemistry Building on the Stanford campus. Chyba will deliver the 23rd annual Bunyan Lecture, hosted by the Astronomy Program in the Department of Physics. His talk, titled "The 21st-Century Search for Extraterrestrial Life," is free and open to the public.

"Whether there is other life is one of the great scientific questions," says Chyba, associate professor (research) in Stanford's Department of Geological and Environmental Sciences. He also is co-director of the Center for International Security and Cooperation (CISAC) within Stanford's Institute for International Studies.

Chyba will devote half his talk to astrobiology -- the study of the origin, evolution, distribution and destiny of life in the universe. Astrobiologists broadly look for life by searching, for example, for evidence on Mars, Europa and other promising places, and analyzing comets for organic molecules capable of seeding life.

Chyba will devote the other half of his talk to the search for intelligent life. With other SETI Institute researchers, Chyba uses the Arecibo radio telescope in Puerto Rico -- the world's largest at 1,000 feet across -- to search for a signal. Researchers must compete for telescope time, and his group gets three weeks of listening time per year.

"We are systematically marching through the thousand nearest sun-like stars looking for artificial signals," says Chyba, who received his doctorate in astronomy in 1991 from Cornell University, where he was a graduate student of Carl Sagan. "We're more than halfway through that search. That search has taken about a decade. There are a couple hundred billion stars in the Milky Way, so looking at the thousand nearest stars is not likely to be successful unless the galaxy is replete with extraterrestrial technical civilizations who are broadcasting."

To cast a wider net and speed up the search, researchers at the SETI Institute and the University of California-Berkeley are building the Allen Telescope Array in Hat Creek, a radio-quiet part of Northern California. Listening for signals 24 hours a day, seven days a week, they will be able to search a million stars in a decade.

Exploring the possibility of life in outer space may help us place ourselves in context in the rest of the universe and may help us better understand life on our own planet, Chyba says. "Our increasing knowledge of life on Earth informs the way we look for extraterrestrial life. Is there only one way to make life, or are there many ways? To some extent, we're starting to answer that question through experimentation. We've not yet made life in the laboratory, but we're getting close to that by some definitions of life in work that's being done in the so-called RNA world."

The greater understanding of terrestrial biology that scientists have gained in the past decade also informs the search for extraterrestrial microbial life, Chyba says. "It makes subsurface environments on Mars and Europa much more plausible."

Chyba chaired the team that set science objectives for the Europa orbiter mission, which aimed to find out if an ocean exists under the icy surface of that Jovian moon. That mission never flew due to escalating costs. While the Galileo spacecraft returned data strongly suggestive of an ocean, Chyba says additional measurements are needed to know with certainty whether an ocean exists under the ice and to begin to understand Europa's subsurface. NASA is considering a new mission that would fly to Europa, as well as Jupiter's moon's Ganymede and Callisto, at the end of this decade, Chyba says.

Chyba's research also explores the effects of comet impacts on the early Earth, as well as Mars and Europa. Comets potentially deliver so-called biogenic elements, such as carbon and nitrogen, to the surface of a world. Since comets may be "extremely organic-rich, maybe 20 percent by mass," he says, "it could mean they played an important role in the origin of life on Earth."

Chyba will speak more about comets during the technical component of the Bunyan Lecture, which he will deliver to faculty and students at 4:15 p.m. Tuesday, April 22, in Room 201 of the Teaching Center in the Science and Engineering Quad. His talk is titled "The Comet-Asteroid Impact Hazard."

The Bunyan Lecture is named for the late James T. Bunyan, a member of the Hoover Institution whose will specified that his estate endow lectures that "inquire into man's changing vision of the cosmos and of human destiny as revealed in the latest discoveries in the fields of astronomy and space exploration."


By Dawn Levy

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