New Way to Make Oxygen Doesn't Need Plants

[scpg02]

New Way to Make Oxygen Doesn't Need Plants

By Tanya Lewis, Staff Writer | October 02, 2014 02:17pm ET

Earth's atmosphere wasn't always full of life-giving oxygen — it was once a choking mixture of carbon dioxide and other gases, more like the atmosphere of Mars or Venus.

It's widely believed that the rise of plants turned that carbon dioxide into oxygen through the chemical reactions of photosynthesis, in a period called the Great Oxygenation Event. But a new study suggests there may be another way to make oxygen from carbon dioxide, using ultraviolet light.

The findings could explain how the Earth's atmosphere evolved, and hint at a way to make oxygen in space, the researchers said. [7 Theories on the Origin of Life]

Even though scientists think plants produced most of the oxygen present on Earth, they suspected some oxygen may have existed before photosynthetic organisms arose, said Cheuk-Yiu Ng, a physical chemist at the University of California, Davis, and co-author of the study published today (Oct. 2) in the journal Science.

~snip~

www.livescience.com/48125-oxygen-made-from-carbon-dioxide.html

[neutrino]

Hey scpg02, here is my take on this. First of, I have a PhD in Chemistry in the area of catalysis and polymers, not atmospheric. However, I got the whiff that (to me) this is less likely than the biological generation of O2. I subscribe to Science and this is what I can say:

This is heavy technical stuff. Bottom line, the study relates to Mars atmosphere observations as high energy UV light hits the atmosphere and generates oxygen, which is known to exist at 0.14% (1,400 ppm) in Mars atmosphere. I don’t think we should consider this a viable mechanism for our atmosphere in the sense of how we got to 21% (20.95% exactly) oxygen (210,000 pm).

From the abstract:

“Photodissociation of carbon dioxide (CO2) has long been assumed to proceed exclusively to carbon monoxide (CO) and oxygen atom (O) primary products. However, recent theoretical calculations suggested that an exit channel to produce C + O2 should also be energetically accessible. Here we report the direct experimental evidence for the C + O2 channel in CO2 photodissociation near the energetic threshold of the C(3P) + O2(X3Sg–) channel with a yield of 5 + 2% using vacuum ultraviolet laser pump-probe spectroscopy and velocity-map imaging detection of the C(3PJ) product between 101.5 and 107.2 nanometers. Our results may have implications for nonbiological oxygen production in CO2-heavy atmospheres.”

Excerpt intro paragraph:

“It is widely accepted that the rise of the oxygen-rich atmosphere on Earth, known as the “Great Oxidation Event,” occurred at ~2.4 billion years ago via multistep photosynthetic processes (Eq. 1)

CO2 + H2O + hv ?(CH2O) + O2 (1)

Here, h is Planck’s constant and n is the frequency. Over the past 40 years, biologists and paleontologists have proposed that free oxygen molecules must have been available in small quantities before the rise of oxygenic photosynthesis in Earth’s prebiotic primitive atmosphere. The only known abiotic production mechanism was through solar vacuum ultraviolet (VUV) photodissociation of CO2 to form CO + O in the early Earth stratosphere, followed by the three-body recombination reactions shown in Eqs. 2 and 3

CO2 + hn(VUV)?CO + O (2)
O + O + M?O2+ M (3)

Here, M is a third body for carrying off the excess energy involved in the formation of the O2 chemical bond. Decades of experimental and theoretical photochemical studies of CO2 have been focused on the detection and understanding of the CO + O photoproduct channels.”

And its technical intensity grows at this point when they start talking about ground state and excitation states of intermediates, symmetry of the intermediates, ab initio calculations (modeling), etc. No pun intended, but there are a lot of greek symbols which I cannot add to this post: sigma, nu, eta, and more.


IF this approach was viable to get more oxygen into an atmosphere, how come Mars still has so much CO2 (95.3%)? It seems to me that the 'livescience' website proposed that this is a potential mechanism. The article does mention a little bit of oxygen coming by this process onto our atmosphere. BTW, the yield of 5+2% is quantum yield, or efficiency of generating oxygen via VUV, not the amount of oxygen that was generated into our atmosphere.

[scpg02]

The base nugget for me was less technical. Presence of Oxygen on another planet does not necessarily mean life is present.

[sigurdur]

Oct 11, 2014 20:10:16 GMT neutrino said:

Hey scpg02, here is my take on this. First of, I have a PhD in Chemistry in the area of catalysis and polymers, not atmospheric. However, I got the whiff that (to me) this is less likely than the biological generation of O2. I subscribe to Science and this is what I can say:

This is heavy technical stuff. Bottom line, the study relates to Mars atmosphere observations as high energy UV light hits the atmosphere and generates oxygen, which is known to exist at 0.14% (1,400 ppm) in Mars atmosphere. I don’t think we should consider this a viable mechanism for our atmosphere in the sense of how we got to 21% (20.95% exactly) oxygen (210,000 pm).

From the abstract:

“Photodissociation of carbon dioxide (CO2) has long been assumed to proceed exclusively to carbon monoxide (CO) and oxygen atom (O) primary products. However, recent theoretical calculations suggested that an exit channel to produce C + O2 should also be energetically accessible. Here we report the direct experimental evidence for the C + O2 channel in CO2 photodissociation near the energetic threshold of the C(3P) + O2(X3Sg–) channel with a yield of 5 + 2% using vacuum ultraviolet laser pump-probe spectroscopy and velocity-map imaging detection of the C(3PJ) product between 101.5 and 107.2 nanometers. Our results may have implications for nonbiological oxygen production in CO2-heavy atmospheres.”

Excerpt intro paragraph:

“It is widely accepted that the rise of the oxygen-rich atmosphere on Earth, known as the “Great Oxidation Event,” occurred at ~2.4 billion years ago via multistep photosynthetic processes (Eq. 1)

CO2 + H2O + hv ?(CH2O) + O2 (1)

Here, h is Planck’s constant and n is the frequency. Over the past 40 years, biologists and paleontologists have proposed that free oxygen molecules must have been available in small quantities before the rise of oxygenic photosynthesis in Earth’s prebiotic primitive atmosphere. The only known abiotic production mechanism was through solar vacuum ultraviolet (VUV) photodissociation of CO2 to form CO + O in the early Earth stratosphere, followed by the three-body recombination reactions shown in Eqs. 2 and 3

CO2 + hn(VUV)?CO + O (2)
O + O + M?O2+ M (3)

Here, M is a third body for carrying off the excess energy involved in the formation of the O2 chemical bond. Decades of experimental and theoretical photochemical studies of CO2 have been focused on the detection and understanding of the CO + O photoproduct channels.”

And its technical intensity grows at this point when they start talking about ground state and excitation states of intermediates, symmetry of the intermediates, ab initio calculations (modeling), etc. No pun intended, but there are a lot of greek symbols which I cannot add to this post: sigma, nu, eta, and more.


IF this approach was viable to get more oxygen into an atmosphere, how come Mars still has so much CO2 (95.3%)? It seems to me that the 'livescience' website proposed that this is a potential mechanism. The article does mention a little bit of oxygen coming by this process onto our atmosphere. BTW, the yield of 5+2% is quantum yield, or efficiency of generating oxygen via VUV, not the amount of oxygen that was generated into our atmosphere.

neutrino
Man, I love reading your response neutrino