Washington, April 9 (ANI): In a new research, scientists have found that a drop in the level of dissolved nickel in seawater may have caused the "Great Oxidation Event" 2.4 billion years ago, in which oxygen levels increased dramatically.
The Earth's original atmosphere held very little oxygen, but this began to change around 2.4 billion years ago when oxygen levels increased during what scientists call the "Great Oxidation Event."
"The Great Oxidation Event is what irreversibly changed surface environments on Earth and ultimately made advanced life possible," said research team member Dominic Papineau of the Carnegie Institution's Geophysical Laboratory.
"It was a major turning point in the evolution of our planet, and we are getting closer to understanding how it occurred," he added.
The researchers, led by Kurt Konhauser of the University of Alberta in Edmonton, analyzed the trace element composition of sedimentary rocks known as banded-iron formations, or BIFs, from dozens of different localities around the world, ranging in age from 3,800 to 550 million years.
Banded iron formations are unique, water-laid deposits often found in extremely old rock strata that formed before the atmosphere or oceans contained abundant oxygen.
As their name implies, they are made of alternating bands of iron and silicate minerals. They also contain minor amounts of nickel and other trace elements.
Nickel exists in today's oceans in trace amounts, but was up to 400 times more abundant in the Earth's primordial oceans.
Methane-producing microorganisms, called methanogens, thrive in such environments, and the methane they released to the atmosphere might have prevented the buildup of oxygen gas, which would have reacted with the methane to produce carbon dioxide and water.
A drop in nickel concentration would have led to a "nickel famine" for the methanogens, who rely on nickel-based enzymes for key metabolic processes.
Algae and other organisms that release oxygen during photosynthesis use different enzymes, and so would have been less affected by the nickel famine.
As a result, atmospheric methane would have declined, and the conditions for the rise of oxygen would have been set in place.
The researchers found that nickel levels in the BIFs began dropping around 2.7 billion years ago and by 2.5 billion years ago was about half its earlier value.
"The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event," said Papineau. (ANI)