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Confused About the Earth's Early Atmosphere...


jimmydasaint
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Recent research seems to indicate information  as follows :

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What was Earth’s atmosphere like a few billion years ago, early in its history? Researchers at Penn State say they’ve found some clues by analyzing iron micrometeorites in ancient soils. These particles from space – a subset of cosmic dust – suggest that carbon dioxide made up 25% to 50% of Earth’s atmosphere 2.7 billion years ago. That’s in contrast to today’s levels of carbon dioxide of around 0.04%. There might also have been less nitrogen then than in our present-day atmosphere; now nitrogen is by far our atmosphere’s primary gas.

The new peer-reviewed findings were published in the journal Proceedings of the National Academy of Sciences on January 21, 2020.

https://earthsky.org/earth/earth-ancient-atmosphere-carbon-dioxide-nitrogen-meteorites

What puzzles me particularly is the question of how long oxygen has been in the atmosphere and its location.  If the early Earth's atmosphere had carbon dioxide, where did the oxygen come from?

Also, I assume that the atmosphere later on was also dominated by water vapour.  Where did the oxygen come from that reacted with the water?

I would appreciate any answer that enables me to learn more about this theoretical topic in an Earth very different to what we have had recently.

 

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1 hour ago, jimmydasaint said:

What puzzles me particularly is the question of how long oxygen has been in the atmosphere and its location.  If the early Earth's atmosphere had carbon dioxide, where did the oxygen come from?

It evolved along with life.

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Most scientists believe that for half of Earth's 4.6-billion-year history, the atmosphere contained almost no oxygen. Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis, perhaps as long ago as 3.5 billion years ago and certainly by 2.7 billion years ago.

 

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2 hours ago, jimmydasaint said:

If the early Earth's atmosphere had carbon dioxide, where did the oxygen come from?

Just to add info. The oxygen in photosynthesis comes from the breaking up of water molecules. The possibility that it came from CO2 has been ruled out experimentally by using isotopic tracers.

https://www.amazon.com/Life-Science-William-K-Purves/dp/0716798565

(chapter 8: Identifying Photosynthetic Reactants and Products)

Water was very abundant in the atmosphere after the late heavy bombardment.

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On 6/15/2020 at 1:36 PM, joigus said:

Just to add info. The oxygen in photosynthesis comes from the breaking up of water molecules. The possibility that it came from CO2 has been ruled out experimentally by using isotopic tracers

Thank you for this I didn't know it. Biology is not my strong suit.  +1

I did find an interesting full description of the chemisty of photosythesis (so far as it is known) inProfessro Downes' book

The Chemistry of Living Cells.

Apparently tracing the carbon with C14 identifies something like 11 stages in the order in which the chemicals must form.

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2 hours ago, studiot said:

Thank you for this I didn't know it. Biology is not my strong suit.  +1

I'm Jack of too many trades (always at risk of spreading too thin), so if you ever catch me in mistake, please do tell me. That book I read twice and did all the questionnaires. Covers most that's needed to get the big picture with a reasonably detailed look at the molecular, and reasonably up to date. They use it at MIT introductory level.

2 hours ago, studiot said:

I did find an interesting full description of the chemisty of photosythesis (so far as it is known) inProfessro Downes' book

The Chemistry of Living Cells.

"Full description" is kind of scary, :D but I'll take a look when as soon as I can.

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