How & Why Earth Went From Purple to Green (Twice!)
Did you know that Earth used to be purple?! Actually, there were TWO periods in Earth’s history during which it likely looked more purple than green like it is today.
The reason land on Earth looks green from space today is plants, but on early Earth, before about ~500-400 million years ago, plants hadn’t evolved yet! So what color was early Earth? To answer this, we first need to understand what makes plants green. It is the pigment plants use for photosynthesis that makes them green.
These pigments actually evolved before plants in microbes like cyanobacteria and later in algae. Therefore, cyanobacteria and algae may have made early Earth look green even before plants. But what about before cyanobacteria? It has been hypothesized that purple pigment-using phototophs, like haloarchaea today, may have evolved before green pigment-using photosynthesizers.
This means that before cyanobacteria came along, Earth may have looked purple! Now, we even think there may have been a second “Purple Earth Event” after the evolution of green cyanobacteria due to ‘purple anoxygenic photosynthesizers’ throughout the boring billion! In this video, I go over both of these hypotheses, the evidence behind them, and the intriguing implications of these Purple Earth Events!
Source: YouTube
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