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[Michaelangelica]

Ancient microbes might have used a molecule other than chlorophyll to harness the Sun's rays — one that would have given the organisms a violet hue.

http://hypography.com/forums/newrepl...ote=1&p=174301

Do any of these live now?
Some plants have red or purple leaves

DasSarma thinks it is because chlorophyll appeared after another light-sensitive molecule called retinal was already present on early Earth.

Retinal, today found in the plum-colored membranes of photosynthetic microbes called halobacteria, absorbs green light and reflects back red and violet light, the combination of which appears purple.

Primitive microbes that used retinal to harness the sun's energy might have dominated early Earth, DasSarma said, thus tinting some of the first biological hotspots on the planet a distinctive purple color.

Being latecomers, microbes that used chlorophyll could not compete directly with those utilizing retinal, but they survived by evolving the ability to absorb the very wavelengths retinal did not use, DasSarma said.

"Chlorophyll was forced to make use of the blue and red light, since all the green light was absorbed by the purple membrane-containing organisms," said William Sparks, an astronomer at the Space Telescope Science Institute (STScI) in Maryland, who helped DasSarma develop his idea.

Chlorophyll more efficient

The researchers speculate that chlorophyll- and retinal-based organisms coexisted for a time.

"You can imagine a situation where photosynthesis is going on just beneath a layer of purple membrane-containing organisms," DasSarma told LiveScience.