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The Search for Life on Other Planets: Creatures Like Us, or Just Microbes?

Posted By Prucia Buscell, Thursday, December 08, 2011

Some scientists think it's hopelessly parochial to search for life on other planets with a focus on finding humans and other large animals.

"Animals are overgrown microbes," Paul Falkowski a biophysicist and biologist from Rutgers University told the New York Times. "We're here to ferry microbes across the planet. Plants and animals are an afterthought of microbes." So as Dennis Overbye writes in his Times article "Hot on Trail of 'Just Right' Far Off Planet," we shouldn't be disappointed if we find our galactic neighbors are alien pond slime and microbes. "After all," Overbye writes, "On Earth microbes were the whole story for almost four billion years, paleontologists say, and now inhabit our intestines as well as every doorknob."

But scientists are learning more about the potential for galactic life. The NASA Kepler search for habitable planets is finding tantalizing information about where the right combinations of water and warmth may make life possible. Even warm and wet is rare. The Times reports that condition occurs now on only one of the eight official planets in our solar system, and on three of the several dozen moons.

Some astronomers have speculated planets orbiting Gliese 581, a red star about 20 light years from earth in the constellation Libra, could be habitable. Then scientists considered the possibilities of life on two more planets, Gliese 581c and Gliese 591d, and another planet right in between them. Watch the National Geographic Channel YouTube presentation about the Gliese potential. In September, scientists announced a planet called HD 85512 that circles a star in the constellation Vela might support life. That star is about 35 light years from earth-and each light year is 5.8 trillion miles. And the Kepler team is now studying possibilities for a patch of stars in the constellation Cygnus, which may be thousands of light years away. But even if there are thousands of habitable planets in the galaxy, according to the Times, only a few hundred of them are within range of any telescope we will have in the foreseeable future.

Donald Brownlee, an astronomer at the University of Washington, says the emergence of large intelligent creatures on earth developed in a turbulent history of accidents and events from asteroid strikes to plate tectonics that is unlikely to be repeated any time soon. He co-authored a book, Rare Earth that asserts we live on a lucky planet.

For fascinating story of scientific evidence and speculation on how the earth made its epic journey around the galaxy for billions of years when conditions for life as we know it were slowly emerging, read Stephen Battersby's story in the New Scientist, "Earth's Wild Ride: Our Voyage through the Milky Way." The earth's rocks are continually changed by erosion and plate tectonics, he writes, so the planet has little record of the huge missiles, asteroids, or lethal radiation that is likely to have assaulted it. But, he writes, "What the Earth forgets, the moon remembers." The moon's soil and rocks lie undisturbed for eons, so an archive of the earth's voyage could lie under the moon's surface, which may some day be accessible for scientific study.

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