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. Last Updated: 07/27/2016

Plants May Be Yellow or Red on Other Planets

CHICAGO -- The same rules that make Earth plants green may make non-Earth plants yellow, red or green -- but likely not blue, U.S. scientists said this week.

They said their findings -- which look at how plants absorb and reflect different types of light -- may help narrow the search for life on planets beyond our solar system. And, as a bonus, they may have answered a basic question about life on Earth.

"We've uncovered maybe the best explanation of why plants are green," said Nancy Kiang, a NASA biometeorologist who led the study, which appears in the journal Astrobiology.

Understanding plant colors on other planets is important as scientists prepare for new information to be generated from giant space telescopes planned by NASA and the European Space Agency to study Earth-sized planets orbiting other stars.

Scientists first studied how light is absorbed and reflected by plants and some bacteria on Earth.

Chlorophyll in plants takes light from the sun and converts it into energy through a process called photosynthesis.

Scientists have long known that most plants on Earth absorb more blue and red light and less green light, but they had not understood why. It turns out that more red light reaches plants on Earth, and blue light is the easiest to absorb. So plants make most efficient use of these two, and that leaves green light as largely superfluous. As a result, plants reflect away relatively more green light, which is why plants appear green.

On other planets, where other colors of the light spectrum might dominate, the plants might soak up more green or even more blue light and reflect back whatever is not needed for energy.