NASA: Plants on other planets not green

Plants on other planets may be predominantly red or yellow, NASA scientists announced Wednesday.

As everyone knows from elementary school science class, plants on Earth are green because they have chlorophyll. Chlorophyll looks green because its molecules absorb mostly blue and red light for photosynthesis, the chemical process by which plants generate food. Our eyes see the remaining reflected light, making plants appear green.

Credit: Caltech illustration by
Doug Cummings

Illustration of what plants could look
like on other planets.

But if the light from a star was different and the light that reached the planet's surface was different, the chemical used for photosynthesis by necessity would have evolved to absorb different parts of the light spectrum. This would naturally result in the reflection of a different color.

NASA scientists announced that they have narrowed what the dominant colors of photosynthesis would be for planets whose atmospheric chemistry is consistent with the star they orbit. For these types of planets, researchers calculated which light would be the most abundant on the surface and hence most favorable to photosynthesis.

Based on that, the scientists found that many plants on other planets could be yellow or red.

"This work broadens our understanding of how life may be detected on Earth-like planets around other stars, while simultaneously improving our understanding of life on Earth," said Carl Pilcher, director of the NASA Astrobiology Institute in a statement. "This approach--studying Earth life to guide our search for life on other worlds--is the essence of astrobiology."

Details of the theory appeared in the March issues of Astrobiology.