Earth’s atmosphere hasn’t always contained the Oxygen (O2) which is now essential for life, it was once a mixture of carbon dioxide and other gases, more like the atmosphere of Mars or Venus.
The only previously proven way that oxygen could have arisen is that the rise of plants turned the carbon dioxide present in the atmosphere into oxygen through the reactions of photosynthesis, in a period called the Great Oxygenation Event. However a new study suggests there may be another way to make oxygen from carbon dioxide, using ultraviolet light and that this method may in fact be partly or wholly responsible for the presence of Oxygen in our atmosphere.
Previously it was thought that a carbon dioxide molecule would split into a CO and an O molecule no matter what wavelengths of light were involved, because that is the path of least resistance and requires the least amount of energy in order to occur. O2 had not previously detected via these methods and therefore presumed to not occur.
However “when you shine C02 with these high wavelengths of light, it can break apart along more than one channel,” said Cheuk-Yiu Ng, a professor of physical chemistry at UC Davis and an author of the paper. “These channels are energy dependent but at the energy we investigated, 5% of these excited CO2 would go on to become C+O2.” The energy required for these 5% is double that which is required to split the molecule into CO + O.
Cheuk-Yiu Ng and his colleagues built a unique instrument to split up carbon dioxide, using ultraviolet light in a vacuum. The device has two lasers — one to split the CO2, and one to detect the fragments produced.
Therefore as certain ultraviolet rays pass through out atmosphere it is possible that 5% of the carbon dioxide molecules that they come in contact with will split and form oxygen molecules.
Not only does this potentially alter how scientists explain how oxygen first came to be in our atmosphere and effect the timeline of Earth’s evolution but the findings have implications for future science. There may be implications on the search for extraterrestrial life, suggesting that merely detecting oxygen in the atmosphere of another planet is not enough to identify the presence of life. The researchers also hinted that it may be possible to use this technique to make oxygen in space or on other planets to aid in space exploration and settlement. Also instead of scientists extracting Oxygen molecules from the atmosphere for medical purposes among many others, we may be able to mass-produce oxygen using carbon dioxide in the future more easily.