Life is dependent on oxygen for survival. Science has shown that O 2 first appeared in Earth's atmosphere around 2.4 billion years ago. But, oxygen was also introduced to the Earth's atmosphere around 100 million years before that. The origin of this earlier breath is still unknown.
New research suggests that volcanoes are likely to be responsible for the shorter oxygenation events preceding the major. Researchers have found a similar increase in mercury levels due to volcanic activity through an analysis of rock records.
Researchers suggest that this activity could have created nutrient-rich volcanic ash and lava fields. Weathering would then release those nutrients into rivers, and coastal areas. This would have allowed cyanobacteria, and other single-celled organisms, to thrive and begin pumping oxygen.
Roger Buick, a geologist at the University of Washington, says that "our study suggests that these transient whiffs of Oxygen" were caused by an increase in oxygen production rather than decreases in oxygen consumption by rocks and other non-living processes.
It's vital because oxygen is the most important driver of the evolution of complex, large-scale life.
Buick and his coworkers looked at drill-cores from Mount McRae Shale Formation in Western Australia. These contain geological timelines that stretch back 2.5 billion years before the Great Oxygenation Event.
Researchers were convinced that both mercury enrichment as well as oxidation weathering played a significant role in the initial oxygen spike.
It's not known exactly where this volcanic activity took place on Earth, but geological records from modern-day India, Canada and other locations support the hypothesis that volcanism and/or lava flows occurred around this time.
For analysis, drill-cores of rock were used. (Roger Buick/University of Washington).
Jana Meixnerov, an astrobiologist at the University of Washington, says that the new basaltic rocks would have slowly dissolved under Archaean conditions, releasing the essential macronutrient, phosphorus, into the rivers.
"This would have fed microbes living in shallow coastal areas and triggered an increase in biological productivity, which would have caused an oxygen spike as a side effect."
Although there may have been other oxygen spikes prior to the Earth's atmosphere transforming in earnest. Even if this study only explains one, it is still useful evidence for looking back at the very beginnings of life on Earth.
As with all studies of this nature, there are implications to research into climate change (showing how life adapts in the face of less oxygen) as well as the search for life elsewhere (showing the kind of atmosphere microorganisms can live in).
There are still many questions about how life began on Earth in its most primitive form, one billion years prior to the Great Oxygenation Event. To answer those questions, we will need to have a better understanding the earth's geology over time.
"What has become apparent in the last few decades is that there are quite a few connections between the solid, living Earth and the evolution life," Meixnerov says.
The research was published in PNAS.
