A new study that analyzed Australian rocks 2.5 billion years old suggests that volcanic eruptions may have spurred population surges of marine microorganisms. This creates the first breaths of oxygen in the atmosphere.
This study could potentially change existing theories about Earth’s early atmosphere.
Earth’s atmosphere became oxygenated about 2.4 billion years ago. The great oxidation event is believed to likely detonate the life forms that photosynthesize, turning carbon dioxide and water into oxygen.
In 2007, scientists at Arizona State University analyzed rocks from the Mount McRae shales in Western Australia. They found a sudden but short-term burst of oxygen around 50 to 100 million years before it became a permanent fixture in the atmosphere.
So far, many studies have confirmed the first short-term oxygen peaks, but they cannot explain the rise and fall of oxygen.
In this new study from the University of Washington, Michigan, and other institutions, scientists analyzed the same ancient rocks for concentration. They analyzed several neutrons in the element mercury emitted by volcanic eruptions. Volcanic eruptions released gaseous mercury into the upper atmosphere – it circulates for a year or two before raining on the Earth’s surface.
The new analysis shows a peak in mercury a few million years before the temporary increase in oxygen.
Co-author Roger Buick, professor of Earth and Space Sciences at UW, said: “Sure enough, in the rock below the transient oxygen peak, we found evidence of mercury, both in its abundance and its isotopes, volcanic eruptions would most reasonably explain this in the atmosphere.”
“There must have been fields of lava and volcanic ash. And these nutrient-rich rocks are said to have withstood wind and rain, releasing phosphorus into rivers that could fertilize nearby coastal areas, allowing oxygen-producing cyanobacteria and other single-celled life to thrive.
The first author, Jana Meixnerová, PhD student at UW in Earth and Space Sciences, said: “There are other nutrients that modulate biological activity on short timescales, but phosphorus is the most important on long timescales.”
“During weathering under the Archean atmosphere, the fresh basaltic rock would have slowly dissolved, releasing the essential macronutrient phosphorus in the rivers. This would have fed the microbes that lived in the shallow coastal areas and triggered increased biological productivity which would have created, as a by-product, a spike in oxygen.
Buick said, “The precise location of these volcanoes and lava fields is unknown, but large, age-old lava fields exist in modern India, Canada and elsewhere.”
“Our study suggests that for these transient bursts of oxygen, the immediate trigger was an increase in oxygen production, rather than a decrease in oxygen uptake by rocks or other non-living processes. This is important because the presence of oxygen in the atmosphere is fundamental – it is the main driver of the evolution of a vast and complex life.
Scientists have noted, “The study suggests how the geology of a planet could affect all life evolving on its surface. Understanding this helps identify habitable exoplanets, or planets outside of our solar system, in the search for life in the universe.
- Jana Meixnerová, Joel D. Blum et al. The abundance of mercury and the isotopic composition indicate subaerial volcanism before the late Archean “breath” of oxygen. DOI: 10.1073 / pnas.2107511118