The Mystery of Earth’s Oxygen
By Carl Zimmer | NYTimes
To Donald E. Canfield, there’s something astonishing in every breath we take. “People take oxygen for granted because it’s just there and we breathe it all the time,” said Dr. Canfield, a geochemist at the University of Southern Denmark. “But we have the only planet we know of anywhere that has oxygen on it.”
What’s even more astonishing is that the earth started out with an oxygen-free atmosphere. It took billions of years before there was enough of it to keep animals like us alive.
Although scientists have been struggling for decades to reconstruct the rise of oxygen, they’re still making fundamental discoveries. In just the past two weeks, for example, Dr. Canfield and his colleagues have published a pair of studies that provide significant clues about some of the most important chapters in oxygen’s history. They’re finding that our weirdly oxygen-rich atmosphere is the result of a complicated dance of geology and biology.
To study the ancient atmosphere, geochemists examine the chemical fingerprints left behind on rocks. Some rocks contain molecules that could have formed only in the presence of oxygen. The more of those molecules geochemists find in a rock, the more oxygen must have been in the atmosphere at the time.
When they look at the oldest rocks on earth, they find no trace of oxygen in the atmosphere. Instead, their research indicates that earth’s primordial air was made up mostly of carbon dioxide, methane and nitrogen. The sun’s rays created some free oxygen by splitting it off from carbon dioxide and other molecules. But the oxygen disappeared almost as soon as it was formed.
That’s because oxygen is an enormously friendly element, forming bonds with a wide range of molecules. It attached to the iron in rocks, for example, creating rust. It joined with hydrogen spewed out from volcanoes to form hydrogen peroxide and other compounds. Our planet, in other words, was a giant oxygen vacuum in its early years.
That changed about three billion years ago. In the Sept. 26 issue of Nature, Dr. Canfield and his colleagues reported the fingerprints of oxygen in rocks from that time period. They estimate that the atmosphere three billion years ago had only 0.03 percent of today’s oxygen levels. That may not sound like much, but it marked a huge shift in the earth’s chemistry.
Sunlight alone couldn’t have put that much oxygen in the atmosphere. Only life could.
By three billion years ago, some microbes had evolved the ability to carry out photosynthesis. Floating at the surface of the ocean, they used energy from sunlight to grow on carbon dioxide and water. They gave off oxygen as waste.
Much of the oxygen released by these photosynthetic microbes was sucked out of the atmosphere by the earth’s vacuum. When microbes died, oxygen reacted with their carbon.
But a tiny amount of oxygen remained behind because some of the organic matter from the dead microbes sank from the surface of the ocean to the sea floor, where oxygen couldn’t react with it. The oxygen remained in the air.
Read the full article at: nytimes.com
Discoveries of Oxygen
Mars had an oxygen-rich atmosphere four billion years ago
Cosmic Dust --"A Clue to Origin of Earth’s Oxygen and Water?"
World’s oldest fossils: Researchers claim bacteria existed on Earth before OXYGEN
Latest News from our Front Page
Immigrants in Hungary Head to German Border on Government Buses and Walking on Foot
Footage showed migrants — frustrated with the Hungarian authorities, who have blocked their way by rail — starting the walk from Budapest toward Germany. Others remained in a standoff with the police.
Budapest - After a day of defiance by increasingly desperate refugees, the government of Hungary metaphorically threw up its hands Friday and offered to bus thousands of migrants to ...
Generation P. Russia awaken!
From Youtube description: The first Russian cult film of the new millenium
Watch a preview here:
Blonde Parade in Latvia
Youtube description: Hundreds of blonde Latvian women marched through the streets of Riga to to lift nation's economy.
Shocking: Young Girls Convulse On The Floor After HPV Shot
Video appears to show widespread adverse reaction to Gardasil vaccine
Shocking video posted to Facebook shows a group of young girls convulsing on the floor after reportedly taking the Gardisil vaccine somewhere in Bolivia.
White Women Are Getting Fed Up
White women speak out against the claim that "White women have things so much easier than every other people."
This video has been flagged as "inappropriate" by Youtube:
Don't miss the Radio 3Fourteen interview with Lana, Sinead and Megan.
|More News » |