Making oxygen before life

About one-fifth of the Earth’s atmosphere is oxygen, pumped out by green plants as a result of photosynthesis and used by most living things on the planet to keep our metabolisms running. But before the first photosynthesizing organisms appeared about 2.4 billion years ago, the atmosphere likely contained mostly carbon dioxide, as is the case today on Mars and Venus.

Over the past 40 years, researchers have thought that there must have been a small amount of oxygen in the early atmosphere. Where did this abiotic (“non-life”) oxygen come from? Oxygen reacts quite aggressively with other compounds, so it would not persist for long without some continuous source.

Now UC Davis graduate student Zhou Lu, working with professors in the Departments of Chemistry and of Earth and Planetary Sciences, has shown that oxygen can be formed in one step by using a high energy vacuum ultraviolet laser to excite carbon dioxide. (The work is published Oct. 3 in the journal Science).

“Previously, people believed that the abiotic (no green plants involved) source of molecular oxygen is by CO2 + solar light — > CO + O, then O + O + M — > O2 + M (where M represents a third body carrying off the energy released in forming the oxygen bond),” Zhou said in an email. “Our results indicate that O2 can be formed by carbon dioxide dissociation in a one step process. The same process can be applied in other carbon dioxide dominated atmospheres such as Mars and Venus.”

UC Davis chemists have shown how ultraviolet light can split carbon dioxide to form oxygen in one step. Credit: Zhou Lu

UC Davis chemists have shown how ultraviolet light can split carbon dioxide to form oxygen in one step. Credit: Zhou Lu

Zhou used a vacuum ultraviolet laser to irradiate CO2 in the laboratory. Vacuum ultraviolet light is so-called because it has a wavelength below 200 nanometers and is typically absorbed by air. The experiments were performed by using a unique ion imaging apparatus developed at UC Davis.

Such one-step oxygen formation could be happening now as carbon dioxide increases in the region of the upper atmosphere, where high energy vacuum ultraviolet light from the Sun hits Earth or other planets. It is the first time that such a reaction has been shown in the laboratory. According to one of the scientists who reviewed the paper for Science, Zhou’s work means that models of the evolution of planetary atmospheres will now have to be adjusted to take this into account.

Coauthors on the paper are, in the UC Davis Department of Chemistry, postdoctoral researcher Yih Chung Chang, Distinguished Professor Cheuk-Yiu Ng and Distinguished Professor emeritus William M. Jackson; and Professor Qing-Zhu Yin, Department of Earth and Planetary Sciences. The work was principally funded by NASA, NSF, and the U.S. Department of Energy.

15 responses to “Making oxygen before life

  1. Has anyone considered the potential application of this finding in the control of CO2 emissions from combustion?

  2. My compliments; this is what we have been looking for, not really to improve Mars but life on earth where the oxygen content has been gobbled up since millennia. Samples from the pyramids showed higher oxygen content, and 120 year old books showed higher oxygen content than today.

    I would hope, such units could be attached to sources of CO2 on earth, like power stations. The bizarre (and expensive) idea of plastering the European and Australian continents with pipelines (Carbon capture and storage) and pump CO2 underground where it is out of sight but can never be out of mind becomes obsolete, horray!

    This invention needs to be in lights, why do I have to discover the topic on a much villified alternative site? Please invite TV crews, or make your own clip and put it on youtube; this could well be world changing. Congratulations again!!!

  3. Great finding. But my question is why similar reaction not happened in Mars and Venus. Can some one explain?

  4. I think the point is the same reaction may well be happening on Venus and Mars: the effect is likely small compared to the oxygen produced by green plants on Earth, but perhaps needs to be taken into account in thinking about how Earth’s atmosphere evolved.

  5. Source-based hi-power UV filtering is great moving ahead. But also, how about shining these lasers in/to the upper atmosphere to break down the CO2 already there that’s been warming the planet for 3 centuries?! Ground-based? Aircraft? Drones? Balloons? Etc.? Solar-powered? Wind-powered? Kids, the disabled (like me), the elderly, on the ground shining up hi-energy UV flashlights even??? Even ‘reversible’ source-based filters for when the smokestack/tailpipe/whatever isn’t emitting (much)??? Wearable UV-flashlight helmets/hats?

    Also, would the atmospheric molecular carbon product reflect some solar energy back into space? Glom together into bigger chunks of carbon? giving us a double bang for our buck? Or fall to the ground and give us all lung cancer? Further acidify surface waters? Increase erosion/smog/respiratory problems? Produce its own chaotic effects on weather and/or climate? ‘geoengineering on the cheap,’ for good/ill??

    Just brainstorming here…. But even if the primary effect — the dissociation of CO2 — is just 5 pct., in a 2-degree Celsius ‘spread’ that’s a whole 0.1C, for what it’s worth. Add-in any new carbon albedo, and it may be even more!

    (C) 2015 Leanne Ceadaoin W.

  6. A matrix of solid state lasers of the proper characteristics, built into the vehicle exhaust system, potentially converting an ICE vehicle into an atmosphere scrubber. 400 ppm CO2 in, 300 ppm out. It would be an exciting breakthrough in vehicle emissions technology.

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