Are alien plants more colourful than earth?

Our land may be green and pleasant but a Nasa team predicts today that foliage on an alien world could be a spectrum of different colours, from yellow to orange or even crimson.

Yellow, orange or even red-dominant plants may grow on planets orbiting stars other than our Sun, according to scientists who believe they have found a way to predict the colour of vegetable life on planets in other solar systems to aid efforts to search for extraterrestrial life.

In two papers in the journal Astrobiology they studied light absorbed and reflected by organisms on Earth, and determined that if astronomers were to look at the light given off by planets circling distant stars, they might predict that some planets have mostly non-green plants.

“We can identify the strongest candidate wavelengths of light for the dominant colour of photosynthesis on another planet,” said Nancy Kiang, lead author, from NASA’s Goddard Institute for Space Studies, New York.

“We want to know if we’re alone in the universe. Photosynthesis produces global-scale signatures of life that can be seen from great distances, for example by future space telescopes. We want to know what signature is photosynthesis or not.”

Working with colleagues at the Virtual Planetary Laboratory, California Institute of Technology, Pasadena, Dr Kiang calculated what the light of a local star would look like at the surface of Earth-like planets whose atmospheric chemistry is consistent with the different types of stars they orbit.

By looking at the changes in that light through different atmospheres, researchers identified colours that would be most favourable for plants to harness that light by the process of photosynthesis.

Scientists have long known that the chlorophyll in most plants on Earth absorbs blue and red light and less green light, appearing green.

Gases in the Earth’s air also filter sunlight, absorbing different colours. As a result, more red light particles reach Earth’s surface than other colours so plants use the red for photosynthesis.

They also use blue particles, because they carry the most energy.

“It makes one appreciate how life on Earth is so intimately adapted to the special qualities of our home planet and Sun,” said Dr Kiang.

“This work made me really appreciate how intimately adapted life on Earth is to the special qualities of our home planet and Sun. It’s thrilling to find if there is life elsewhere in the universe, and humbling to realize how much we should treasure our life on Earth.”

But not all stars have the same distribution of light colours as our Sun. As a result, photosynthesis on these alien worlds will not necessarily look the same as on our home world.

This new research narrows the spectrum of colours that scientists would expect to see when photosynthesis is occurring on these so called extrasolar planets.

Each planet will have different dominant colours for photosynthesis, based on the planet’s atmosphere where the most light reaches the planet’s surface.

The dominant photosynthesis might even be in the infrared. On Earth, for example, there is a type of bacterium that inhabits murky waters where there is little visible light, and so they use infrared radiation.

The team looked at a variety of star types both hotter (more blue) and cooler (more red or infrared) than our Sun, and with photosynthesis that produces oxygen and photosynthesis that does not.

For a bluish star, with oxygen produced, the pigments will absorb blue and “could appear the range of yellow, orange or red or some combination of these colours,” she told The Daily Telegraph.

For star types much cooler than our Sun, plants will likely perform photosynthesis by absorbing in the infrared, like the purple bacteria that inhabit murky waters here on Earth.

What visible light the plants reflect that our eye can see is not so certain.

“They could be black, grey, yellow, or what have you,” she said.

“This work will help guide designs for future space telescopes that will study extrasolar planets, to see if they are habitable, and could have alien plants,” said Victoria Meadows, an astronomer who heads the VPL, where scientists are using computer models to simulate Earth-size planets and how they may appear to space telescopes.

“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 Nasa’s Astrobiology Institute at NASA Ames.

“This approach - studying Earth life to guide our search for life on other worlds - is the essence of astrobiology.”

Are alien plants more colourful than earth? Are alien plants more colourful than earth? Reviewed by Bobby on 7:29 AM Rating: 5

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