Plant life search in outer space

 

Scientists are seeking biosignatures found in the light spectrum leaking out to Earth for clues to life on extrasolar planets.

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They are speculating on what kind of photosynthesis might occur on such planets and what the extrasolar plants might look like.

It could be that the plants are black, said Robert Blankenship, Lucille P. Markey Distinguished Professor in Arts and Sciences at Washington University in St Louis.

Scientists who speculate on plant life and what might constitute photosynthesis 'out there' say that plant colour depends on the size and light intensity that the planet feeds off from its star, or sun, as well as the extrasolar planet's atmospheric chemistry.

Plants on Earth are green because of chlorophyll, which harnesses the energy of the Sun to make sugars for metabolism, but our plants aren't completely efficient — they waste a little bit of light.

"Ideally, what you want is a black molecule that absorbs all of the light," Blankenship said.

"There could be another system developed on an extrasolar planet where plants are completely black if the spectrum of light that's available to organisms is different from the light available to organisms on Earth.

"Then, for sure, the plants will have different types of pigments tuned to absorb those wavelengths of light available on the other world."

Plants could be key to what other planets look like

Blankenship is co-author of two papers recently published in the journal Astrobiology, which detail the kinds of clues that researchers are looking for and explore theories of what these other worlds might be like.

He is also part of a NASA working group based at the Jet Propulsion Laboratory called the Virtual Plant Laboratory.

He and his colleagues are studying light that comes from stars and extrasolar planets to infer their composition.

They can see clues that suggest the presence of water vapour, oxygen or carbon dioxide, for instance.

One key biosignature is the existence of disequilibrium — the simultaneous presence of things that should not coexist on a dead world.

The presence of methane and oxygen together on an extrasolar planet, for instance, would be a strong smoking gun for the possible existence of life.

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