The Mystery of Earth’s Oxygen
2013 10 09

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




Related Articles
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

What happened to Journalist Serena Shim? Assassinated? Find out what happened to Serena, Press TV director calls on Turkey
2014 10 21
Press TV news director Hamid Reza Emadi says the “suspicious death,” of the news channel’s correspondent in Turkey is a tragedy for “anyone who wants to get the truth.” Emadi made the remarks in an interview with Press TV on Sunday following Serena Shim’s death across the border from Syria’s Kurdish city of Kobani, where the ISIL terrorists and Kurdish fighters ...
Ancient Roman Nanotechnology Inspires Next-Generation Holograms for Information Storage
2014 10 21
The Lycurgus Cup, as it is known due to its depiction of a scene involving King Lycurgus of Thrace, is a 1,600-year-old jade green Roman chalice that changes colour depending on the direction of the light upon it. It baffled scientists ever since the glass chalice was acquired by the British Museum in the 1950s, as they could not work ...
Rapid Geomagnetic Reversal Possibility: Confirmed
2014 10 21
From the video: "The scientists who conducted the study are still unsure why the magnetic field is weakening, but one likely reason is the Earth’s magnetic poles are getting ready to flip, said Rune Floberghagen, the ESA’s Swarm mission manager. In fact, the data suggest magnetic north is moving toward Siberia." Tune into Red Ice Radio: Ben Davidson - Suspicious0bservers: Space Weather ...
Georgia Guide Stone 2014 cube stone removal
2014 10 21
From: Youtube: Was it all just a gag? it seems the cube stone just happens to be made out of the same Elberton granite that the rest of this morbid monument is made from.
Secret Project Created Weaponized Ebola In South Africa In The 1980s
2014 10 21
“No records are available to confirm that the biological agents were destroyed.” Operating out of South Africa during the Apartheid era in the early 1980’s, Dr. Wouter Basson launched a secret bioweapons project called Project Coast. The goal of the project was to develop biological and chemical agents that would either kill or sterilize the black population and assassinate political enemies. ...
More News »