EARTH.COM - Strange as it sounds, some scientists think the earliest life forms on Earth may have painted our planet in shades of purple rather than the green we see today.
This idea, known as the Purple Earth hypothesis, suggests that single-celled organisms depended on a less complex molecule than chlorophyll to harness sunlight.
NASA-supported work points to retinal as that pivotal molecule, which lent these microbes a vivid violet color.
The concept has been investigated by astrobiologist Dr. Edward Schwieterman of the University of California, Riverside, and professor Shiladitya DasSarma of the University of Maryland.