When we think of extrasolar Earth-like planets, the first tendency is to imagine weird creatures like Jar Jar Binks, Chewbacca, and, if those are not bizarre enough, maybe even the pointy-eared Vulcan, Spock, of Star Trek fame. But scientists seeking clues to life on extrasolar planets are studying various biosignatures found in the light spectrum leaking out to Earth to speculate on something more basic and essential than the musical expertise of Droopy McCool. They are speculating on what kind of photosynthesis might occur on such planets and what the extrasolar plants might look like.

Paint it black

It could be the plants are black, says Robert Blankenship, Ph.D., Lucille P. Markey Distinguished Professor in Arts & Sciences at Washington University in St. Louis. But it all depends on what size and light intensity of star or sun the planet feeds off, and the extrasolar planets 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 arent 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 thats 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. Blankenship is co-author of two papers recently published in the journal Astrobiology. The papers detail the kinds of clues that researchers are looking for and explore theories of what these other worlds might be like.

Blankenship is part of a NASA working group based at the Jet Propulsion Laboratory called the Virtu
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Contact: TonyFitzpatrick
tony_fitzpatrick@wustl.edu
314-935-5272
Washington University in St. Louis
19-Jun-2007