Wednesday, April 11, 2007

The purple grass of home

Early life on earth might have been purple, not green:

... 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.

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