When Paul Butler began hunting for planets beyond our solar system, few people took him seriously, and some, he says, questioned his credentials as a scientist.

Researcher Jay Quade looks for signs of microbes in Chile’s Atacama Desert. (By Julio L. Betancourt — U.s. Geological Survey Via Associated Press)

That was a decade ago, before Butler helped find some of the first extra-solar planets, and before he and his team identified about half of the 300 discovered since.

Biogeologist Lisa M. Pratt of Indiana University had a similar experience with her early research on “extremophiles,” bizarre microbes found in very harsh Earth environments. She and colleagues explored the depths of South African gold mines and, to their great surprise, found bacteria sustained only by the radioactive decay of nearby rocks.

Indiana University biogeologist Lisa M. Pratt and Edward J. Weiler, chief of NASA’s science division, think life in other solar systems is possible and, perhaps, detectable. (Indiana University – Indiana University)

“Until several years ago, absolutely nobody thought this kind of life was possible — it hadn’t even made it into science fiction,” she said. “Now it’s quite possible to imagine a microbe like that living deep beneath the surface of Mars.”

The experiences of these two researchers reflect the scientific explosion taking place in astrobiology, the multi-disciplined search for extreme forms of life on Earth and for possibly similar, or more advanced, life elsewhere in the solar system and in distant galaxies.

The confidence that alien life will ultimately be found is strong enough to have kindled formal discussions among scientists, philosophers, theologians and others about the implications that such a find would have for humanity’s view of itself, and how to prepare the public for the news, should it come.

“There’s been a fundamental shift in the thinking of the scientific community on the question of life-forms beyond Earth,” Pratt said.

Edward J. Weiler, one of the founders of NASA’s astrobiology program and now chief of the agency’s science division, goes even further.

Astrobiology’s most intensive effort at the moment is focused on Mars, where NASA’s robotic lander Phoenix is digging up soil and ice in a search for organic material. (Bill Ingalls – Associated Press)

“We now know the number of stars in the universe is something like 1 followed by 23 zeros,” he said. “Given that number, how arrogant to think ours is the only sun with a planet that supports life, and that it’s in the only solar system with intelligent life.”

Although humans have speculated for centuries about the possibility of extraterrestrial life, astrobiology began as a formal NASA program only in the mid-1990s, created in the excitement that followed the discovery of a meteorite from Mars that was initially thought to contain fossils or other evidence of microscopic organisms (a conclusion now generally rejected). The field has nonetheless grown quickly. More than 700 scientists and graduate students — including molecular biologists, chemists, planetary scientists and cosmologists — showed up at a NASA-sponsored astrobiology conference in California this past spring.

Many schools have growing astrobiology programs, and planet-hunter Paul Butler often travels from his base at the Carnegie Institution in the District to Chile, Hawaii and Australia to work with other astronomers at big telescopes. He estimates that 1,000 to 2,000 scientists now work in the field.

Few believe that the discovery of extraterrestrial life is imminent. However, just as scientists long theorized that there were planets orbiting other stars — but could not prove it until new technologies and insights broke the field wide open — many astrobiologists now see their job as to develop new ways to search for the life they are sure is out there.

The most intensive effort at the moment is focused on Mars, where NASA’s robotic lander Phoenix is digging up soil and ice in search of organic material. The automated lab has excited scientists by finding many of the nutrients needed for life, although it has not found anything that was, or is, living. Also, photos and other data from NASA’s Mars Reconnaissance Orbiter produced dramatic new evidence this month that the planet was once home to vast lakes, flowing rivers and a variety of other wet environments that had the potential to support life.

Much more is on the way. NASA will launch the Kepler probe next year, and its central goal will be to identify Earth-like, and possibly habitable, planets around distant stars. Japanese astronomers plan to band together to observe one star in great detail because of hints that it could have an orbiting planet with life. And preliminary work is underway for joint NASA-European Space Agency probes of Europa and Titan, moons of Jupiter and Saturn with conditions that might support life.

The basic roadmap for the United States’ astrobiology effort, and about $40 million in seed money, came from NASA. It funds the NASA Astrobiology Institute in California and teams of researchers in universities nationwide, as well as efforts to develop new technologies for exploring extreme forms of life in Mars- or moon-like environments on Earth. The yearly astrobiology budget was halved after reaching a peak of $60 million in 2005, but pressure from the space science community is pushing that figure back up.

Butler and Pratt are part of Astrobiology Institute-funded teams, as are scientists who are creating virtual planets to model what the atmosphere of a distant inhabited planet might look like, and others studying how very simple organisms evolve into more complex ones. This kind of basic research is often used by NASA, as well as other astronomers and explorers for extraterrestrial life, to design space missions and plan ground-based observations.

John Rummel, director of the NASA astrobiology program, said the program is changing the way people think about life on Earth and beyond.

“The context for life is much broader than just what we see on Earth,” he said. “Organic material is falling from the sky all the time, and we’re learning that what happens out there is very important down here. Who knows: Maybe life on Earth came from Mars billions of years ago, when it had liquid water on its surface.”

Rummel said that the discovery of many varieties of extremophiles on Earth, coupled with a better understanding of some potentially habitable environments on other planets or moons, leads him to believe that life beyond Earth will be found, with ramifications comparable to Copernicus’s 15th-century discovery that Earth is not the center of the universe. “The Copernican revolution continues,” Rummel said.

Tales of canals and green men on Mars, UFOs and “Star Trek” characters have long captured the imagination, but finding microbes or evidence of other life beneath the surface of Mars or on the moons of Jupiter or Saturn is another matter entirely. Even if the first extraterrestrial life to be identified were primitive rather than intelligent, experts said, the discovery would be a major milestone in human history.

“If any extraterrestrial life is found in our solar system and we can determine it has no relation to life on Earth, then the assumption has to be that life of all sorts is quite common throughout the galaxies,” Butler said.

To some, debating the implications of discovering extraterrestrial life is premature at best, because — all UFO “sightings” aside — none has ever been found.

Two Viking missions to Mars in the 1970s to search for organic material did not identify any — although they were unable to dig below the rugged and parched Martian surface into the ground where scientists now think that water and possibly life could be found. In addition, the private group SETI, or Search for Extraterrestrial Intelligence, has been broadcasting radio messages to hoped-for intelligent aliens for years and listening for a response — sometimes with NASA support — but has been met so far with silence. And what some consider the rush to declare that the meteorite from Mars contained fossil remains has become an object lesson in the importance of confirming the science before making any declarations about extraterrestrial life.

What is different now, researchers say, is that they know so much more about extreme life-forms on Earth that could quite comfortably live on other planets. In addition to South Africa’s radioactivity-driven bacteria, extremophiles have also been found living near super-hot sulfurous steam vents at the deep ocean floor, in pools composed almost entirely of acid, and recently two miles below the surface of the Greenland ice sheet. All get little or no energy from the sun, which sustains virtually all other life-forms, and their survival makes it more conceivable that microbes could live in the sub-surface ice or water on Mars and Europa.

Having identified more than 300 planets outside the solar system, researchers are also convinced that planets and solar systems — some probably similar to ours — are present and perhaps quite common, elsewhere in the universe. The next step is to find extrasolar planets in the “habitable zone” of their solar systems; planets whose size, makeup and distance from their sun might allow life to develop.

In addition, the Hubble Space Telescope and other instruments have given researchers new data about the evolution and structure of the universe — information that makes it increasingly appear to be “fine-tuned” for life.

Lord Martin Rees, England’s Astronomer Royal made that argument as the keynote speaker at NASA’s spring astrobiology conference — saying that life could not exist on Earth or anywhere else if the basic physical dynamics of the universe were not almost precisely what they are. Slight changes in the strength of the electrical force that holds atoms together, of the pull of gravity, or of the total mass of the universe would have made it difficult for stars to form and create the heavy elements essential for life, and impossible for them to remain active long enough to support the process of evolution.

Many religious thinkers see this fine-tuning as an argument for the existence of a creator, but Rees and other cosmologists offer a different explanation: that our universe is but one in a world of multiple (or infinite) universes. However it came into being, Rees argued, our universe is inherently life-supporting, and there is no reason to believe that that potential has been realized only on Earth.

The excitement now in the field, and its central challenges, were expressed in a report last year by the National Research Council, which assembles experts to study scientific issues and problems.

“The Limits of Organic Life in Planetary Systems” report — also known simply as “Weird Life” — concluded: “The likelihood of encountering some form of life in subsurface Mars and sub-ice Europa appears high. . . . The committee sees no reason to exclude the possibility of life in environments as diverse as the aerosols above Venus and the water-ammonia [mixture] of Titan.”

The report then warned that “nothing would be more tragic to the American exploration of space than to encounter alien life and fail to recognize it, either because of the consequences of contamination or because of the lack of proper tools and scientific preparation.”

Astrobiology’s goal is to make sure that does not happen.

By Marc Kaufman
Washington Post Staff Writer
Sunday, July 20, 2008