for National Geographic News
Does life exist on other planets? Seeking an answer, scientists are busy developing the next generation of tools that will examine atmospheric chemicals of Earth-like planets for signs of life.
For decades, scientists have searched the skies in vain for signs of extraterrestrial life. On April 8, 1960 Frank Drake, now Chairman of the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California, aimed a radio antenna a two nearby stars and listened for distant communications.
Drake heard no signals that day, but SETI has continued in earnest ever since. The search has primarily been based on the use of radio telescopes such as the Arecibo telescope in Puerto Rico. While conventional astronomers use the telescope for much of the year, SETI researchers are allotted a small amount of time each year to listen for messages similar to those broadcast by a disc jockey.
Scientists' desire to detect signals that any life form might radiate into spacenot just life that has evolved the technology to broadcast radio waveslies at the root of the next generation of search technologies.
Malcolm Fridlund, a scientist with the European Space Agency (ESA) in the Netherlands, said that if other planets follow a similar evolutionary pattern as Earth, it is much more likely that they will be inhabited by dinosaurs or bacteria rather than by something that can count.
Fridlund is working on ESA's Darwin Project, which aims to expand the search for life on planets orbiting suns outside our solar system to the detection of chemical signals that life might give off, such as oxygen, methane, and water vapor.
"We have defined a scientific search for our origins and future, remembering that life has existed on this planet for at least 3.5 billion years, while intelligent life not very long indeed," he said.
The efforts of ESA are complemented by a similar program at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, known as the Terrestrial Planet Finder (TPF). The effort seeks to search 50 to 150 nearby stars for Earth-like planets with signatures of life in their atmosphere.
"Darwin and TPF are joined at the hip," said Charles Beichman, the project scientist for the TPF program at the California-based research institute.
The thrust behind Darwin and TPF is an idea first put forward by British scientist James Lovelock in the 1970s. Lovelock posited that by just breathing, life on Earth affects the composition of the atmosphere. He suggested that looking for similar distributions of atmospheric gas on other planets could be a way to search for life.
To find the planets, the telescopes may take advantage of a technology known as interferometry, which combines the power of several small telescopes to produce a final sharp and detailed image.
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