Search for Alien Life Gains New Impetus

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.