UW experts squelch hope of finding folks on that final frontier

It's a thought that grips most everyone who stares into the unfathomable depths of a star-speckled night: Is there anybody out there?

The odds, say Peter Ward and Don Brownlee, are probably more remote than you think.

Earth, they contend, is simply too special, the result of myriad physical conditions missing from most of the universe, with just enough time and other circumstances to let complicated life arise.

"We consider it to be random chance and luck," said Brownlee, a University of Washington astronomer. "Mostly luck."

Hence the title of their book, "Rare Earth: Why Complex Life is Uncommon in the Universe," published this month (Copernicus, $27.50).

The book throws a wet blanket on the mounting optimism of the past half-century, which has seen amino acids created in a beaker, evidence of fossilized bacteria in a Martian meteor and the first glimpse of planets outside our solar system.

The two authors have already begun fielding criticism that they might hurt efforts to find extraterrestrial life and serve up ammunition to creationists who hold that Earth is not only rare, but unique.

"Somehow, I don't think we really appreciated that this was going to raise such hackles," said Brownlee.

"An awful lot of astrobiologists, NASA itself, are threatened by this," said Ward, a paleontologist specializing in mass extinctions. "If we're right, if there's not a lot of life out there, people might say, `Why bother going to look?' We don't want that approach. We hope we're wrong. But what we try to do is say, `There's a straw man here. Prove us wrong if you can.' "

`Rare earth factors'

There's no argument among scientists that a plethora of factors has to be just right for complex life to develop. Drawing on a variety of sources, Ward and Brownlee compile what they call the "rare earth factors." In the cosmic crap shoot of life, they make for a big fistful of dice.

Among their claims:

We are the right distance from our star. We can have liquid water on our surface, but not so much that we are totally underwater, and we aren't so close to the sun that its gravity creates a tidal lock that stops our rotation.

The sun is just the right mass - big enough to last a long time but not so bigit throws off too much radiation.

Our solar system's planets aren't so big that they throw off our orbit. But we do benefit from a big planet like Jupiter, which sweeps comets and asteroids from our path.

Our own planet has just the right mass and heat for plate tectonics, needed to build a land mass.

Our moon keeps us from keeling over on our axis, perturbing our climate.

We have enough carbon for life but not so much that the greenhouse effect wreaks havoc.

We have a nice location in the galactic neighborhood, away from the black holes, radiation and comets of the interior, but well in from the edge, where there is a scarcity of the heavy elements needed to build life.

Ward and Brownlee actually believe microbial life may be abundant in the universe. The paradox, they say, is that Earth is the rare place where there's not too much or too little of the important ingredients for our type of life. Things are just right.

Lowering expectations

The factors needed for life in the universe were weighed nearly 40 years ago by astronomer Frank Drake, who multiplied things like the number of stars in our galaxy, the fraction of stars with planets and the number of habitable "earths." Drake used the equation to estimate there are 10,000 civilizations in the Milky Way alone. The late astronomer Carl Sagan put the number at 1 million.

Ward and Brownlee don't calculate a number of civilizations in their book, but Ward in an interview put it at between one - that would be Earth - and 100.

Geoff Marcy, a professor of astronomy at the University of California at Berkeley and co-discoverer of 20 planets outside our solar system, estimates there are 100 billion Earth-sized planets in the Milky Way.

But numbers like that may have led astrobiologists to be too optimistic, he said. With the severe limits detailed by Ward and Brownlee, the number of those planets capable of offering a toehold to life may well shrink to one, Marcy said.

"I'm sad to say there are people that will be downcast about this conclusion, but the truth is, it's scientifically sound," he said.

But Drake, now president of the SETI (Search for Extraterrestrial Intelligence) Institute, the Mountain View, Calif.-based effort to search for radio signals from distant civilizations, said Ward and Brownlee underestimate the ability of life to adapt to extreme conditions.

"There are insects that have invented antifreeze," he said. "There are creatures that live where there is no light, creatures that live where there is no water for literally tens of years. . . . To think you need an Earthlike environment to have life is just not supported by the biology we see on Earth."

Discouraging estimates of life beyond Earth surface periodically, he said, "but it has not really set back our programs and our sources of funds."

Creationists aren't likely to make too much of Ward and Brownlee's work either, said Danny Faulkner, a professor teaching astronomy and physics at the University of South Carolina at Lancaster and adjunct faculty member of the Institute for Creation Research in San Diego.

"They're arguing for a remote possibility," Faulkner said. "I think we're arguing for a zero probability. That doesn't sound like a big difference, but it is."

Athena Andreadis, Harvard neurologist and author of "To Seek Out New Life: The Biology of Star Trek," noted that those who want to respond to Ward and Brownlee face a problem the authors themselves faced: There's not a lot of evidence to work with. In fact, our planet is the only one we have with which to build theories of complex life on other planets.

"Astrobiology may be unique in the sciences as having no data," Andreadis said, a common lament.

Evidence of extraterrestrial civilizations might be right under our noses, she said, but we may simply lack the ability to read it. We have yet to decipher whether a whale song is a form of intelligence, she said. It would be even harder to see intelligence in an intergalactic plasma.

Further research ahead

The lack of evidence of extraterrestrial life makes further research all the more important, say Ward, Brownlee and Scott Hubbard, associate director for astrobiology and space programs at the NASA Ames Research Center in Moffett Field, Calif.

Toward that end, NASA hopes to build a telescope called the Terrestrial Planet Finder, which will block the light of nearby stars to seek the spectral signatures of key Earthlike substances like water, carbon and oxygen. Scientists are also looking forward to the day NASA brings back samples of Mars soil, which may at one time have seeded Earth with life, or looks for life in the ice-covered waters of Europa, one of Jupiter's larger moons.

"The only way we'll settle this is by going to places like Mars or Europa or using space telescopes to look for Carl Sagan's `pale blue dot' " - his shorthand for an Earthlike planet, Hubbard said.

Until then, talk of unearthly civilizations is more often than not the stuff of fiction.

"We really hope in our heart of hearts that we're completely wrong," said Ward. "We want there to be lots of life out there. We want every star around us to have intelligent life. But as scientists, here's what the evidence in our short lives and our narrow imaginations tells us. We say at the end of the book, perhaps this book is simply a failure of imagination."

Eric Sorensen's phone message number is 206-464-8253. His e-mail address is esorensen@seattletimes.com ------------------------- Authors to speak

University of Washington scientists Peter Ward and Don Brownlee will discuss their book, "Rare Earth: Why Complex Life is Uncommon in the Universe," at 7 p.m. Thursday at Third Place Books, 17171 Bothell Way N.E., in Lake Forest Park.