Billions of years ago, the Blue Planet wasn’t exactly blue.
Researchers have found that Earth’s first oceans may not have been blue at all like today.
Instead, they may have gleamed in shades of green for billions of years.
Although Earth formed about 4.5 billion years ago, life didn’t emerge on the planet for at least another 800 million years.
Yet, even in its lifeless stage, the planet was already covered in vast oceans, where hydrothermal vents pumped out ferrous iron.
As some of the earliest organisms to perform oxygenic photosynthesis, cyanobacteria—commonly known today as algae—emerged around 4 billion years ago.
Unlike modern plants that rely solely on chlorophylls, these ancient microbes also harnessed the sun’s energy using specialized pigments called phycobilins.
With the rise of cyanobacteria—key players in Earth’s evolutionary history—around 2.4 billion years ago, a transformative period known as the Great Oxidation Event began.
During this time, oxygen began accumulating in Earth’s atmosphere, setting the stage for life as we know it. However, one mystery puzzled researchers for years—why did cyanobacteria need phycobilins in the first place?
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