April 13, 2009

Google Logo Add Us On GoogleAdd SciAm

Breathing Easy Thanks to the Great Oxidation Event

A report in the journal Nature reveals one of the reasons why Earth's atmosphere went from oxygen-poor to habitable 2.4 billion years ago--a drop in oceanic nickel killed microbes that produce methane. Cynthia Graber reports

Illustration of a Bohr atom model spinning around the words Science Quickly with various science and medicine related icons around the text

Join Our Community of Science Lovers!

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

[The following is an exact transcript of this podcast.]

The Earth’s original atmosphere would have been unpleasant—deadly in fact—to any organisms that breathe oxygen. There wasn’t any. Not until about 2.4 billion years ago anyway. That’s the time of what scientists call the Great Oxidation Event. Now researchers believe they’ve found clues as to what may have caused the change. They published their report in the April 9 edition of the journal Nature.

Researchers analyzed trace elements in sedimentary rock from dozens of sites. Turns out nickel was 400 times more abundant in primordial oceans than in today’s waters. Microorganisms called methanogens love nickel-rich water, and they release methane into the atmosphere. Methane prevents a buildup of oxygen.

Scientists testing the rocks saw that around 2.7 to 2.4 billion years ago, ocean-dissolved nickel dropped off. This corresponds to the Great Oxidation Event. Lack of nickel could have killed off methanogens and left room for algae and other life forms that release oxygen during photosynthesis.

Researchers don’t know exactly why nickel decreased—possibly because of the cooling and solidifying of the Earth’s mantle. But the nickel disappearance is one more clue about how the planet went from suffocating to a place where a terrestrial tetrapod could take a deep breath.

—Cynthia Graber

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American

Subscribe
Breathing Easy Thanks to the Great Oxidation Event