Search for Alien Life Gains New Impetus

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.