Some scientists propose that Earth was once covered in shades of purple instead of green. The idea suggests early life forms used a different molecule for photosynthesis than today’s chlorophyll.

The Purple Earth hypothesis suggests that early single-celled organisms used retinal, a simpler molecule, instead of chlorophyll, creating a purple hue across the planet.

NASA-backed research supports this hypothesis, with scientists like Dr. Edward Schwieterman and Shiladitya DasSarma exploring retinal’s role in early Earth life.

Chlorophyll, the green pigment in plants, is essential for photosynthesis, helping plants convert sunlight into energy. Without it, life as we know it wouldn’t exist.

Before chlorophyll, retinal likely powered photosynthesis on early Earth. During this period, atmospheric oxygen was scarce, but sunlight still powered purple microbes.

Organisms like halobacterium, purple microbes, thrived in salty environments like the Great Salt Lake. They used retinal for photosynthesis, creating their vibrant hue.

Over time, organisms evolved to use chlorophyll, leading to more efficient photosynthesis. This shift contributed to the Great Oxygenation Event, turning Earth’s surface green.

Although Earth is mostly green, places like the Dead Sea still show purple hues thanks to halobacterium, demonstrating how purple life persists in extreme conditions.

The Purple Earth hypothesis encourages scientists to seek diverse biosignatures on other planets, expanding our search for life beyond Earth and revealing unexpected paths of evolution.