Where Does Most of the Earth's Oxygen Come From?

[Still_Small_Voice]

Where does most of the Earth's Oxygen come from?  Scientists agree that there’s oxygen from ocean plants in every breath we take. Most of this oxygen comes from tiny ocean plants – called phytoplankton – that live near the water’s surface and drift with the currents. Like all plants, they photosynthesize – that is, they use sunlight and carbon dioxide to make food. A byproduct of photosynthesis is oxygen.

Scientists believe that phytoplankton contribute between 50 to 85 percent of the oxygen in Earth’s atmosphere. They aren’t sure because it’s a tough thing to calculate.

Read more if you find this subject interesting at:  https://earthsky.org/earth/how-much-do-oceans-add-to-worlds-oxygen

[anatess2]

The answer to the question is Ocean... 5th Grade Science, Oxygen Cycle, dude.

[Vort]

30 minutes ago, anatess2 said:

The answer to the question is Ocean... 5th Grade Science, Oxygen Cycle, dude.

That's true, but the fundamental question is: Whence derives the elemental oxygen in our atmosphere? The answer is without doubt water, which means the oceans. But the bulk of that oxygen must have been liberated well before what we call the "oxygen cycle" was well-developed. Anaerobic bacterial activity must have been responsible in the first instance for creating an atmosphere filled with then-toxic oxygen, before life developed which actually used that oxygen for its own benefit. Amazing, really. (Perhaps "mind-blowing" or "incomprehensible" would be better words.)

[Jamie123]

11 hours ago, Vort said:

Anaerobic bacterial activity must have been responsible in the first instance for creating an atmosphere filled with then-toxic oxygen, before life developed

I don't understand - surely "bacterial activity" implies the existence of bacteria, which implies life already had developed (unless of course you mean eukaryotic life - which if I remember rightly requires bacteria to serve as mitochondria).

This website is quite interesting: https://www.earthfacts.com/atmosphere/historyearthatmosphere/. It suggests that the earliest forms of life fed on amino acids, producing methane and carbon dioxide, and later life forms (the earliest "plants") used photosynthesis to turn this into sugar (for energy) with oxygen as a by product - and that is where the oxygen came from. 

But wait a minute: how does the sugar become energy? Surely this requires some form of "burning", and does not burning require oxygen?

On the Wikipedia page on photosynthesis it gives the formula for sugar as C₆H₁₂O₆ - which of course contains its own oxygen. So does sugar burn without an external supply of oxygen? Can you burn sugar in a vacuum?

In that case, why can't you burn other things in a vacuum? Like wood for example. Wood is (I believe) cellulose, which is C₆H₁₀O₅ - which again contains oxygen. So why does that not burn without oxygen?

Interesting. (More interesting than work.)

Edited September 6, 2019 by Jamie123

[anatess2]

14 hours ago, Vort said:

That's true, but the fundamental question is: Whence derives the elemental oxygen in our atmosphere? The answer is without doubt water, which means the oceans. But the bulk of that oxygen must have been liberated well before what we call the "oxygen cycle" was well-developed. Anaerobic bacterial activity must have been responsible in the first instance for creating an atmosphere filled with then-toxic oxygen, before life developed which actually used that oxygen for its own benefit. Amazing, really. (Perhaps "mind-blowing" or "incomprehensible" would be better words.)

Guys, guys... you can't discuss science like that going so far back more than 100 years because then you'd contradict the prevailing science that the Amazon is the earth's source of oxygen and that Bolsonaro's forest fires are going to kill Planet Earth.  

[Vort]

4 hours ago, Jamie123 said:

15 hours ago, Vort said:

Anaerobic bacterial activity must have been responsible in the first instance for creating an atmosphere filled with then-toxic oxygen, before life developed

I don't understand - surely "bacterial activity" implies the existence of bacteria, which implies life already had developed (unless of course you mean eukaryotic life - which if I remember rightly requires bacteria to serve as mitochondria).

Poor wording on my part. I meant, "before life developed as we see around us today." It seemed to make sense in my own mind at the moment I wrote it. Let this be a lesson, children: Proofread!

[Emmanuel Goldstein]

there is hundreds of years worth in the atmosphere. But most of it comes from the ocean.

[Traveler]

Mostly it is believed that oxygen is cycled through photo carbon based photosynthesis back into the atmosphere in order for organisms that require aerobic means (oxygen) as the primary means of using fuels - which includes most life forms in the animal kingdom.  This means that in order for earth to support life - both carbon and oxygen are necessary elements in the atmosphere and the oceans.  Interestingly carbon monoxide is lethal to oxygen breathing life forms but lucky for all us a free oxygen atom will combine with carbon monoxide creating carbon dioxide that is exactly what the plants need.  But carbon dioxide is the greenhouse gas that is claimed to cause global warming.

It would make sense the most of the oxygen comes from the seas that cover over 2/3 of the planet.  But before we discount trees - Trees are a prime engine of weather and climate on the less than 1/3 of the planet land mass.  Evaporated water requires a cooling condensation to turn water vapor (gas) into liquid.   photosynthesis is a process of using energy and thus causes cooling.   So - not only do plants create oxygen - they provide the means of cooling which is the means of changing water vapor to rain and rain also induces cooling - or if the cooling is sufficient - will create snow.  It is good to get water vapor out of the atmosphere in the form of rain because water vapor is the single most significant greenhouse gas that all by itself is more than all other greenhouse gases in our atmosphere combined.   

In short the quickest and surest way to end all life as we know it on our planet is to significantly reduce atmospheric carbon - which is exactly what the "Green New Deal" has promised to do.

 

The Traveler