(November 20, 2015) ASU
scientist Ariel Anbar helped lead research team solving the puzzle of Earth’s
Great Oxidation Event
Earth's oxygen-rich atmosphere emerged as transient “whiffs”
in shallow oceans around 2.5 billion years ago, according to new research from
Canadian and US scientists.
These whiffs of oxygen likely happened in the following 100
million years, changing the levels of oxygen in Earth’s atmosphere until enough
accumulated to create a permanently oxygenated atmosphere around 2.4 billion
years ago – a transition widely known as the Great Oxidation Event.
“One of the questions we ask is: ‘Did the evolution of
photosynthesis lead directly to an oxygen-rich atmosphere? Or did the
transition to today's world happen in fits-and-starts?" said Ariel Anbar,
President's Professor in Arizona State University’s School of Earth and Space
Exploration (SESE) and the School of Molecular Sciences (SMS). “How and why
Earth developed an oxygenated atmosphere is one of the most profound puzzles in
understanding the history of our planet.”
The findings are presented in a paper published this month in
Science Advances from researchers at University of Waterloo, University of
Alberta, Arizona State University, University of California Riverside, and
Georgia Institute of Technology. The team presents new isotopic data showing
that a burst of oxygen production by photosynthetic cyanobacteria temporarily
increased oxygen concentrations in Earth's atmosphere.
“The onset of Earth's surface oxygenation was likely a
complex process characterized by multiple whiffs of oxygen until a tipping
point was crossed,” said Brian Kendall, a professor of Earth and Environmental
Sciences at the University of Waterloo, who led the study. “Until now, we
haven’t been able to tell whether oxygen concentrations 2.5 billion years ago
were stable or not. These new data provide a much more conclusive answer to
that question.”
Kendall was a visiting student, postdoctoral fellow, and
faculty research associate at Arizona State University from 2006-2012, where he
worked with Anbar.
The new data support a hypothesis proposed by Anbar,
Kendall, and other collaborators in 2007. In Western Australia, they found
preliminary evidence of these oxygen whiffs in black shales deposited on the
seafloor of an ancient ocean.