September 14, 2006 - Space

sagar: Author=’Deborah Byrd’ program=” video=”The artist’s image above depicts the Earth 3.9 billion years ago. The days were shorter and the sun was dimmer, shining as a red orb through an orange brick-colored sky. A single ocean is thought to have covered Earth then, colored muddy brown: a place that absorbed incoming meteors and comets bombarding the early Earth. At this time in Earth’s history, Earth is thought by scientists to have possessed a turbulent, steamy atmosphere composed mostly of nitrogen, carbon dioxide and hydrogen sulfide.

And so begins a description of Earth’s past by astronomers “Lisa Kaltenegger”:http://cfa-www.harvard.edu/~lkaltenegger/ and “Wesley Traub.”:http://www.mos.org/cst-archive/article/4830/6.html

Kaltenegger and Traub have developed what they are calling an “alien I.D. chart” that will provide “the signposts astronomers will look for when examining truly Earth-like worlds” for signs of alien life.

They’re basing their chart on geologic records indicating that Earth’s atmosphere has changed dramatically during the past 4.5 billion years, in part because of life forms developing on our planet.

Mapping what gases comprised Earth’s atmosphere during its history, Kaltenegger and Traub propose that by looking for similar atmospheric compositions on other worlds, scientists will be able to determine if that planet has life on it, and if so, that life’s evolutionary stage.

Kaltenegger explains, “As daunting as this challenge sounds, I do believe in the next few decades we will know whether or not our little blue world is all alone in the universe or if there are neighbors out there waiting to meet us.”

Read more: “Astronomers Reveal First Alien I.D. Chart”:http://www.spaceref.com/news/viewpr.html?pid=20818 from “spaceref.com”:http://www.spaceref.com .

Written by Deborah Byrd

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