CDHS

NASA's Search For Life

Beyond Earth

by Dr. John Delano

This is the recap by Frank Robinson of a talk given at the February 11th, 2007 CDHS monthly meeting.

Dr. John W. Delano spoke to us about the chances for life existing elsewhere in the Universe. If you missed it, you should be kicking yourself, because it was really a terrific and engaging program.

Dr. Delano is a Distinguished Teaching Professor at the State University of New York’s Department of Earth and Atmospheric Sciences. This cumbersome title requires him to carry business cards of extra large size. However, it does not burden him with ponderousness in his speaking manner.

People have long wondered about whether we are alone in the Universe. Until recent times, it has been idle speculation; but lately we have developed tools for tackling this issue on a scientific basis.

We start from the calculation that there are 10¹¹ galaxies in the Universe, each typically having upwards of 200 billion stars. That makes for 10²² stars. That’s a big number—one followed by 22 zeroes. We are also finding that planets are pretty common (about one for every five solar-type stars), which implies an estimated 10²¹ to 10²³ planets.

So, now we can ask the key questions: out of so many planets, how many might have life? Is planet Earth an unusual environment, or common? How common is complex life? And, is intelligence an inevitable result of life’s evolution?

Dr. Delano looked at the Earth’s early history, based on studying certain crystals that embed information about what Earth was like 4.4 billion years ago—when it was a wee little infant only a hundred million years old (that’s very young in cosmic terms). And the answer is that the Earth then was already very much like the Earth today, and ready to spit up life (to continue the infant metaphor). And this at least, he stressed, was not unique; “it’s what planets do.”

Now, he defined “life” as a chemical system able to transfer its molecular information and evolve. And he noted that life on Earth utilizes the commonest chemical elements in the Universe. At the top of the list is carbon; and it also happens that carbon has an especially rich repertoire of chemical behavior.

Of course, Mars being our closest planetary neighbor, and not radically different from Earth, it has been a focus of our searching for extraterrestrial life. The verdict is not yet in; but Dr. Delano deemed it telling that Mars has certainly had water, and its atmosphere has been found to contain localized concentrations of methane. This is significant because methane disappears quickly, so its presence suggests that something is producing it currently.

Looking beyond our immediate neighborhood, we have now detected about 200 planets orbiting other stars. How do we find them? One way is to track the wobbles of stars caused by the gravitational effects of planets. Another way is to look for dimming of stars caused when planets pass in front of them. The U.S. is launching the Kepler project into space to utilize the latter method surveying 100,000 stars over four to six years, which we hope will detect 100 to 500 new planets. And what we are really looking for is earth-sized planets, which cruder past methods have been incapable of detecting.

One important thing that we have learned already, though, is that Earth is apparently rare in one critical respect, its near-circular orbit. Most extra-solar planets seem to have highly elliptical orbits. The significance of this is that such planets would have very variable climates, swerving from deep freezes to roasting, which is rather inconvenient for life. Simple unicellular life could still make it under such conditions, especially by exploiting subsurface environments; but it would be a very challenging situation for any kind of complex life forms, such as humanists.

Nevertheless, even if we suppose that only one planet in a million is as hospitable to life as Earth is, that would still mean around 10¹⁶ such planets in the Universe, which is a pretty adequate number, bigger than the number of Chinamen in Shanghai (by a lot, actually). The bad news, though: such planets would be rather far apart, and we’d have to shout very loud to communicate with any people on them.

Dr. Delano concluded his presentation by telling us to spare a moment to look at the stars in the sky and to look around us, appreciatively, at the planet we inhabit. “This place,” he said, “is really quite remarkable.”

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