How & Why Earth Went From Purple to Green (Twice!) | GEO GIRL

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! ;D

GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, & donate to support the channel if you'd like!)

0:00 Life on Early Earth
1:15 Photosynthesis on Early Earth
2:56 Contrasting Colors of Photopigments
4:49 Purple Earth Hypothesis
5:25 Phototrophy vs Photosynthesis
6:22 Purple vs Green Phototrophs
9:43 From Purple To Green Earth
11:24 Evidence for Purple Earth
14:29 Rise of Photosynthesis
14:57 Second Purple Earth?
19:01 Transition to Green Earth
19:41 Using Pigments to Find Aliens?

References:
DasSarma & Schwieterman, 2018: https://api.semanticscholar.org/Corpu...
Zhao et al., 2023: https://doi.org/10.3389/fmicb.2022.10...
Philippi et al., 2021: https://doi.org/10.1038/s41467-021-25...
Sparks et al., 2006: https://www.researchgate.net/publicat...
Johnston et al., 2009: https://doi.org/10.1073/pnas.0909248106
Lyons et al., 2021: https://doi.org/10.1089%2Fast.2020.2418
Earth System History: https://amzn.to/3v1Iy0G

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Bamboo toilet paper: https://shrsl.com/3cvku
Bamboo paper towels: https://shrsl.com/3cvkw
Compostable tableware: https://shrsl.com/3cvkz
Compostable trash bags: https://shrsl.com/3cvl0
Bamboo cutlery + straw! : https://shrsl.com/3cwfl
Eco-Friendly Tote (great for grocery shopping!): https://shrsl.com/3cwfp
Reusable straws + cleaning brushes (my fav!): https://shrsl.com/3cwft
Eco-friendly laundry detergent: https://shrsl.com/3cwgo

Directly offset your carbon footprint with Wren: https://shrsl.com/3d0t2
(Just click link, press get started, take the free C footprint quiz, then choose how much you want to reduce your footprint by donating to the C sequestration projects they're funding!)

Non-textbook books I recommend:
Oxygen by D. Canfield: https://amzn.to/3gffbCL
Brief history of Earth by A. Knoll: https://amzn.to/3w3hC1I
Life on young planet by A. Knoll: https://amzn.to/2RBMpny
Some assembly required by N. Shubin: https://amzn.to/3w1Ezm2
Your inner fish by N. Shubin: https://amzn.to/3cpw3Wb
Oxygen by N. Lane: https://amzn.to/3z4FgwZ
Alien Oceans by K. Hand: https://amzn.to/3clMx1l
Life's Engines: https://amzn.to/3w1Nhke

Tools I use as a geologist/teacher/student:
Geology field notebook: https://amzn.to/3lb6dJf
Geology rock hammer: https://amzn.to/3DZw8MA
Geological compass: https://amzn.to/3hfbdLu
Geological hand lens: https://amzn.to/3jXysM5
Camera: https://amzn.to/3l6fGRT
Carbon-neutral pencil bag: https://shrsl.com/3cvjv
Carbon-neutral backpack: https://shrsl.com/3cvkc

Disclaimer: Links included in this description might be affiliate links. If you purchase a product or service with the links that I provide I may receive a small commission, but there is no additional charge to you! Thank you for supporting my channel so I can continue to provide you with free content each week! And as always, let me know your topic suggestions in the comments down below!