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Photosynthesis holds key to life on other planets |
| TheAllINeed.com |
(NC&T/UEA) They used a modelling study to explain for the first time the 300 million year gap between the evolution of oxygen-producing organisms and the first significant rise in atmospheric oxygen levels.
Oxygen-producing photosynthesis evolved at least 2.7 billion years ago, but scientists have long debated why it took a further 300 million years before the so-called 'Great Oxidation' - probably the biggest chemical change in the Earth's history - took place.
In a paper in science journal Nature, Colin Goldblatt, Tim Lenton, and Andrew Watson of UEA's School of Environmental Sciences, explain that after oxygen-producing photosynthesis evolved, the atmosphere could have existed in either a 'low' or 'high' oxygen state. The low oxygen concentrations would have persisted until a critical point, when the atmosphere would flip to high oxygen levels.
A relatively small environmental change, such as a decrease in volcanic outgassing or an increase in burial of dead organic matter in sediments, could have triggered a switch between these states, causing oxygen levels to rocket. This ultimately made complex life possible on Earth.
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"This could have implications for the possibility of life on other planets," said Colin Goldblatt. "We tend to think that we would be able to see the evidence of photosynthesis on another planet as oxygen in the atmosphere, accompanied by ozone which is easier to detect. What our result shows is that photosynthesis can tick along for a very long time with hardly any oxygen or ozone in the atmosphere."
"So if we were to find another Earth-like planet somewhere else in the galaxy with no oxygen or ozone in its atmosphere, it could still have photosynthetic life."
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