New Technologies Emerge in Search for Alien Life

John Roach
for National Geographic News
February 7, 2003
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.

Search Programs

Scientists' desire to detect signals that any life form might radiate into space—not just life that has evolved the technology to broadcast radio waves—lies 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.

Viewing in the infrared, these images will be of a spectrum of colors representing the different chemicals in the planet's atmosphere.

"What we are looking for is an atmosphere out of chemical equilibrium," said Fridlund. "Currently the Earth's atmosphere is out of such an equilibrium through its oxygen."

Scientists believe that without life, all free oxygen in the atmosphere would disappear within just four million years because it reacts so easily with other chemicals. So if scientists detect a planet with a lot of oxygen, it could be a sign that it harbors life.

Other signatures the scientists hope to search for include water vapor and carbon dioxide. Later, they might scan for chlorophyll, the chemical compound found in plants which allows plants to convert solar energy from the sun into energy through the process known as photosynthesis. The detection of chlorophyll in space would provide strong evidence of active photosynthesis—an extraterrestrial life.

SETI Today

As Darwin and TPF scientists plan for their missions to launch sometime in the middle of the next decade, the SETI Institute is moving forward with plans in collaboration with the University of California at Berkeley to build a massive radio telescope known as the Allen Telescope Array, which will be dedicated to SETI.

Currently the SETI Institute is limited to available time on radio telescopes, which is mostly allocated to other kinds of radio astronomy. The SETI Institute only gets three or four weeks of observation time each year.

The array will be a 350 dish interferometer and will simultaneously conduct SETI research and radio astronomy, said Edna Devore, the SETI Institute's director of education and outreach. The array is anticipated to be online in 2005.

The institute is also partnering with NASA's Ames Research Center in Moffett Field, California, on the Kepler Mission, which will launch in 2007 and for the first time allow scientists to search for Earth-sized planets in orbit around distant stars.

"The results of the Kepler Mission is essential for NASA and ESA in planning Darwin and TPF because Kepler will discover that planets like Earth are common or rare," said Devore.

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