Distant Planets Could Have Plants of "Alien" Colors

April 12, 2007

Scientists may be able to determine the color of extraterrestrial plant life while studying distant planets, according to a pair of new studies.

Researchers have developed a way to analyze the light emitted by a given planet's parent star and determine how that light interacts with various chemicals in the planet's atmosphere.

This gives scientists an idea of the wavelengths, or colors, of light that reach the planet's surface.

On Earth, red light is most abundant, while blue light is most energetic, or useful to plants. So plants tend to absorb these colors and reflect the less useful green light, said Nancy Kiang, a biologist at NASA's Goddard Institute for Space Studies in New York.

But other stars may emit different wavelengths of light, and their planets may have different chemicals in their atmospheres, she explained. So the dominant colors reaching the surfaces of other planets may be unlike those on Earth.

This means that distant worlds could theoretically feature plants that are red, yellow, or blue.

"We're actually predicting what pigments absorb … but you can conjecture what range of colors they might wind up reflecting since they're not absorbing them," Kiang said.

Search for Alien Plant Life

Kiang and colleagues used computer models to develop their method of studying light on distant worlds. Two related papers on the process appear in the March issue of the journal Astrobiology.

The models simulate different kinds of light emitted by stars that are hotter and cooler than the sun. The models then weigh how that light would interact with a planet's chemistry, what light would reach the ground, how plants would use that light, and other variables.

Co-author Victoria Meadows is an astrobiologist at the California Institute of Technology in Pasadena. She said the research will also help scientists detect life on extrasolar planets.

(Read related story: "Earthlike Planet Spied in Distant Solar System" [January 26, 2006].)

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