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.
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.