Atmospheric oxygenation three billion years ago

Sep 25, 2013
This image shows some of the rocks that Sean Crowe and his colleagues studied. Credit: Nic Beukes

Oxygen appeared in the atmosphere up to 700 million years earlier than we previously thought, according to research published today in the journal Nature, raising new questions about the evolution of early life.

Researchers from the University of Copenhagen and University of British Columbia examined the of three-billion-year-old soils from South Africa – the oldest soils on Earth – and found evidence for low concentrations of . Previous research indicated that oxygen began accumulating in the atmosphere only about 2.3 billion years ago during a dynamic period in Earth's history referred to as the Great Oxygenation Event.

"We've always known that by led to the eventual oxygenation of the atmosphere and the evolution of aerobic life," says Sean Crowe, co-lead author of the study and an assistant professor in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at UBC.

"This study now suggests that the process began very early in Earth's history, supporting a much greater antiquity for oxygen producing photosynthesis and aerobic life," says Crowe, who conducted the research while a post-doctoral fellow at Nordic Center for Earth Evolution at the University of Southern Denmark in partnership with the centre's director Donald Canfield.

There was no oxygen in the atmosphere for at least hundreds of millions of years after the Earth formed. Today, the Earth's atmosphere is 20 per cent oxygen thanks to photosynthetic bacteria that, like trees and other plants, consume carbon dioxide and release oxygen. The bacteria laid the foundation for oxygen breathing organisms to evolve and inhabit the planet.

"These findings imply that it took a very long time for geological and to conspire and produce the oxygen rich atmosphere we now enjoy," says Lasse Døssing, the other lead scientist on the study, from the University of Copenhagen.

Explore further: Better forecasts for sea ice under climate change

More information: Paper: dx.doi.org/10.1038/nature12426

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Torbjorn_Larsson_OM
2.3 / 5 (3) Sep 25, 2013
Yeah, well. The recent phylogeny of cyanobacteria matches the GOE very well. It would also complicate the recently riddled GW heating of the faint Archean Sun.

This is then an extraordinary claim.
MrVibrating
1.8 / 5 (5) Sep 25, 2013
I may be largely ignorant of the issues here but it's the 2nd most common element in the planet's constitution, after iron.... so how can its early atmospheric abundance be so enigmatic..? Could it not have come from water vapour in the high atmosphere being blasted by radiation / cosmic rays etc - IIRC a similar process is credited with dehydrating Mars..?
Q-Star
5 / 5 (5) Sep 25, 2013
I may be largely ignorant of the issues here but it's the 2nd most common element in the planet's constitution, after iron.... so how can its early atmospheric abundance be so enigmatic..? Could it not have come from water vapour in the high atmosphere being blasted by radiation / cosmic rays etc - IIRC a similar process is credited with dehydrating Mars..?


Actually oxygen is the most abundant element in the planet's constitution. Iron is about fourth or fifth in the mantle/crust.

But the reason it is enigmatic in the atmosphere, is because O2 (and O3) are very highly reactive and unstable molecules. A biological mechanism is the only good explanation for the high abundance of molecular oxygen. Without it being produced in copious quantities, it would have reacted and combined with other elements, iron, carbon, magnesium, aluminum, etc. long, long ago.
MrVibrating
not rated yet Sep 26, 2013


Actually oxygen is the most abundant element in the planet's constitution. Iron is about fourth or fifth in the mantle/crust.

I stand corrected, thanks.

But the reason it is enigmatic in the atmosphere, is because O2 (and O3) are very highly reactive and unstable molecules. A biological mechanism is the only good explanation for the high abundance of molecular oxygen. Without it being produced in copious quantities, it would have reacted and combined with other elements, iron, carbon, magnesium, aluminum, etc. long, long ago.

Yes i understand this, but not why various inorganic energy sources - such as high altitude radiation acting on water vapour - are insufficient.. for instance couldn't volcanism release it? Or lightning discharges? Presumably these have already been eliminated.. i'm just curious why..
Anda
not rated yet Sep 26, 2013
"three-billion-year-old soils from South Africa – the oldest soils on Earth"

Untrue... There are 4 by old ones. Just search the web.
Q-Star
5 / 5 (1) Sep 26, 2013
Yes i understand this, but not why various inorganic energy sources - such as high altitude radiation acting on water vapour - are insufficient.. for instance couldn't volcanism release it? Or lightning discharges? Presumably these have already been eliminated.. i'm just curious why..


Elemental oxygen has an affinity to combine with other elements, it's the result of the arrangement of it's valence electrons, oxygen has 8 electrons, six in the outer shell, this arrangement makes it very easy for it to form a compound with another element.

The most efficient way to reverse that process in nature is for biological metabolism to act on organic molecules in aerobic respiration cycles.

Any oxygen freed in inorganic or physical processes is minuscule compared to oxygen's propensity to combine with other elements. Basically it's because inorganic reactions tend to join free oxygen with with other elements, not the other way around.
philw1776
1 / 5 (2) Sep 26, 2013
Any data on what the % of oxygen was over time? Or is this as yet too difficult to quantify pre-Cambrian.
Torbjorn_Larsson_OM
not rated yet Sep 28, 2013
@Franklin: The phylogeny of cyanobacteria I pointed to ("Evolution of multicellularity coincided with increased diversification of cyanobacteria and the Great Oxidation Event", Schirrmeister et al, PNAS EE 2012) is consistent with first running out of Fe, then Mn.

Dissolved Fe was reduced by early life >~ 3.8 Ga according to Isua BIFs. That metabolism could be adopted by the first anaerobic photophiles, as evidenced by extant such in some deep and nutrient poor inland waters.

When Fe became scarce the first photosynthesizers likely evolved to use remaining dissolved Mn as electron sink in chlorophyll complexes. When Mn in turn became scarce those complexes could evolve to retain Mn permanently and instead pave off electrons on water dissociation complexes.

The Huronian glaciation is believed to have been _a result_ of the GOE, as GW gases would have disappeared. (E.g. methane.)
Torbjorn_Larsson_OM
5 / 5 (1) Sep 28, 2013
@philw1776: AFAIK people looks at Mn oxidation states. Previous results have been that free oxygen would have been very scarce, in the ppm range or so.
MrVibrating
not rated yet Sep 29, 2013
Elemental oxygen has an affinity to combine with other elements...

lol thanks but as i said i understand this already.

The most efficient way to reverse that process in nature is for biological metabolism to act on organic molecules in aerobic respiration cycles.
But it takes the same amount of energy regardless of the source, be it a bacterium or a cosmic ray - ie. a few eV, depending on the specific reaction.

It's not like the environment was energy-starved before life came along..

Any oxygen freed in inorganic or physical processes is minuscule compared to oxygen's propensity to combine with other elements.
But then ditto for organic reactions - the vast majority of Earth's O2 is still locked up inside it..

Basically it's because inorganic reactions tend to join free oxygen with with other elements, not the other way around.

Yes, again, O2 has high valance, but life isn't the only source of endothermic reactions. Evidently something's been missed.

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