Climate change and the rise of atmospheric oxygen

Today's climate change pales in comparison with what happened as Earth gave birth to its oxygen-containing atmosphere billions of years ago. By analyzing clues contained in rocks, scientists at the Carnegie Institution's Geophysical Laboratory have found that the initial rise of oxygen (O₂) was transitory and that its final emergence may have been linked to volcanoes and catastrophic glaciations.

"Rocks contain fingerprint-like clues to the past environment through specific variations in elements such as sulfur," explained Carnegie researcher Shuhei Ono. "Our Earth didn't start out with oxygen in the atmosphere. It probably contained methane and hydrogen, but no oxygen. We think that there were microbes in the oceans, before the oxygenated atmosphere, which would have used methane for energy. Measuring sulfur isotopes--different versions of the atom with the same number of protons, but a different number of neutrons--in rock samples provides a sensitive way to monitor ancient oxygen levels. Oxygen first appeared on the surface of the Earth when microbes developed the capacity to split water molecules to produce O₂ using the Sun's energy. This is a bit advanced biochemistry, but we think this biological revolution emerged sometime before 2.7 billion years ago," he continued.

Ono looked at sulfur isotopes from South African drill-core samples covering the time interval from 3.2 to 2.4 billion years ago. Around 2.9 billion years ago, the methane-dominated atmosphere provided a greenhouse effect and kept the planet warm. His analysis suggests that when oxygen first appeared in the atmosphere, around that time, it would have reacted with the methane, destabilizing the atmosphere and triggering the Mozaan-Witwatersrand glaciation.

The oxygen atmosphere wasn't here to stay, however. "It was a raucous time," stated Carnegie's Andrey Bekker. "Volcanoes peppered the Earth's surface, belching gases and particulates into the atmosphere. That material rained back to the surface and oceans, affecting ocean chemistry and the ocean and atmospheric cycles. We looked at sulfur isotopes in shale and pyrite from Western Australia and found that between 2.47 and 2.463 billion years ago oxygen levels started to rise. But the intense volcanic activity made it almost disappear again. Despite these fits and starts, our oxygen atmosphere prevailed in the end."

The work is presented in several talks at NASA's Astrobiology Science Conference (AbSciCon) 2006 in Washington, D.C., March 26-30. See http://abscicon2006.arc.nasa.gov/ for details.

Source: Carnegie Institution

Related stories:

Building a New Rocket for the Nation
The Ares I rocket, America's next flagship in space, is now in development by NASA and its industry partners, and soon will carry human explorers and new missions of discovery to the moon and beyond. And thousands of American workers in 32 states and Puerto Rico are helping make it happen.
Scientists point to forests for carbon storage solutions
Scientists who have determined how much carbon is stored annually in upper Midwest forests hope their findings will be used to accelerate global discussion about the strategy of managing forests to offset greenhouse gas emissions.
Bad sign for global warming: Thawing permafrost holds vast carbon pool
Permafrost blanketing the northern hemisphere contains more than twice the amount of carbon in the atmosphere, making it a potentially mammoth contributor to global climate change depending on how quickly it thaws.
Volcanic eruptions wiped out ocean life 93 million years ago
University of Alberta scientists contend they have the answer to mass extinction of animals and plants 93 million years ago. The answer, research has uncovered, has been found at the bottom of the sea floor where lava fountains erupted, altering the chemistry of the sea and possibly of the atmosphere.
Researchers Find Ancient Evidence of 'Snowball Earth'
LSU scientist Huiming Bao, along with colleagues from UCLA and China, recently discovered some of the first atmospheric evidence in support of the “Snowball Earth” hypothesis. This theory suggests that Earth was entirely covered by ice during the Cryogenian period, which took place from about 790 to 630 million years ago. Their findings were reported in the May 22 issue of Nature.
Ice cores map dynamics of sudden climate changes
New, extremely detailed data from investigations of ice cores from Greenland show that the climate shifted very suddenly and changed fundamentally during quite few years when the ice age ended. Researchers from the Niels Bohr Institute of University of Copenhagen have together with an international team analysed the ice cores from the NorthGRIP drilling through the Greenland ice cap, and the epoch-making new results have been published in the highly esteemed scientific journal Science and in Science Express.
Toxic to aliens -- but key to health of planet
Scientists at the University of Leicester are using an ingredient found in common shampoos to investigate how the oxygen content of the oceans has changed over geologically recent time.
Researchers witness assembly of molecules critical to protein function
A Virginia Tech research group lead by two biochemistry graduate students has isolated proteins responsible for the iron-sulfur cluster assembly process and witnessed the necessary protein interactions in vivo – within a cell. They have captured pathway intermediates and observed protein interactions between the two major players in iron-sulfur cluster assembly.

News discussion:

Space & Earth science news