"There's been a fundamental shift in the thinking of the scientific community on the question of life-forms beyond Earth," Pratt said.
"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."
"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.
"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.
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.
Bonus link: NASA telescopes spot star "factory."