When water met iron deep inside the Earth, did it create conditions for life?

November 14, 2017, Carnegie Institution for Science
An illustration from the paper showing oxygen and hydrogen cycling in the deep Earth. Credit: Carnegie Institution for Science

Reservoirs of oxygen-rich iron between the Earth's core and mantle could have played a major role in Earth's history, including the breakup of supercontinents, drastic changes in Earth's atmospheric makeup, and the creation of life, according to recent work from an international research team published in National Science Review.

The team—which includes scientists from Carnegie, Stanford University, the Center for High Pressure Science and Technology Advanced Research in China, and the University of Chicago—probed the chemistry of and water under the extreme temperatures and pressures of the Earth's .

When the action of plate tectonics draws water-containing minerals down deep enough to meet the Earth's iron core, the extreme conditions cause the iron to grab oxygen atoms from the water molecules and set the hydrogen atoms free. The hydrogen escapes to the surface, but the oxygen gets trapped into crystalline iron dioxide, which can only exist under such intense pressures and temperatures.

Using theoretical calculations as well as laboratory experiments to recreate the environment of the core-mantle boundary, the team determined that iron dioxide can be created using a laser-heated diamond anvil cell to put materials under between about 950 and 1 million times normal atmospheric pressure and more than 3,500 degrees Fahrenheit.

"Based on our knowledge of the chemical makeup of the slabs that are drawn into the Earth's deep interior by , we think 300 million tons of water could be carried down to meet iron in the core and generate massive iron dioxide rocks each year," said lead author Ho-kwang "Dave" Mao.

These extremely oxygen-rich solid rocks may accumulate steadily year-by-year above the core, growing into gigantic, continent-like sizes. A geological event that heated up these iron dioxide rocks could cause a massive eruption, suddenly releasing a great deal of oxygen to the surface.

The authors hypothesize that such an oxygen explosion could put a tremendous amount of the gas into the Earth's atmosphere—enough to cause the so-called Great Oxygenation Event, which occurred about 2.5 billion years ago and created our oxygen-rich atmosphere, conditions that kickstarted the rise oxygen-dependent life as we know it.

"This newly discovered high-temperature and intense-pressure water-splitting reaction affects geochemistry from the deep interior to the atmosphere" said Mao. "Many previous theories need to be re-examined now.

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1 / 5 (1) Nov 14, 2017
So, 1) early Earth already had active plate tectonics, unlike what most recent research is thinking facts are pointing at and 2) Great Oxygenation had nothing to do with development of photosynthesis?
3.7 / 5 (3) Nov 14, 2017
Well, this remains just a hypothesis.

I'm not sure if this idea will get any wider traction, as, even with strong subduction, most crust would be melted and dissociated --along with any water it contained-- well before it got close enough to the mantle-core boundary, especially so since most of the minerals in crust rocks are not hydrated --the water is present in sediments that are subducted with the crust.

I've read here recently about ultra low velocity zones located at the core-mantle boundary, and the possibility of them being much more liquid than ordinary mantle material, and therefore possibly the cause of mantle plumes --or some of them, anyway-- so perhaps this is speculation along those lines.

At any rate, I could be wrong of course, but my understanding is that crust material doesn't plunge to that depth before being reincorporated into the mantle, and/or melting and rising back crustwards.
1 / 5 (7) Nov 14, 2017
Since this is just speculation that doesn't even begin to address all the issues involved in getting life from non-living materials, one can simply give a wry smile and move on.

It should be obvious from the makeup of living things that it's not possible for life to arise from dead materials via random physical and chemical processes. It's just not going to happen because the way chemistry works just kills it in the bud.

There is currently no way to obtain just the right combination of environmental factors that will create a dedicated chain of exclusively left-handed chiral amino acids based on top of an exclusively right-handed set of sugar bases. All in the right order.
Whenever chiral elements form naturally they form in both left and right handed forms and it takes extensive knowledge and dedicated tools to separate them. Never mind stringing the correct elements together is the right sequence.
Plus - Not enough energy exist to try all combos.
5 / 5 (8) Nov 14, 2017
Since this is just speculation that doesn't even begin to address all the issues involved in getting life from non-living materials, one can simply give a wry smile and move on
Of course because as we all know, jehovah just waved his magic wand and poof! there was life.

So why should we bother to look any further? This only makes people like fred feel uncomfortable and thats not very nice is it?
5 / 5 (7) Nov 14, 2017
#F "It should be obvious..."
No, it isn't. In fact, the more you look, the more possible processes emerge...
not rated yet Nov 19, 2017
Apart from iron dioxide, iron hydride is also produced in the reaction, and it should dissolve in the core, as it has a lower melting point than pure iron. 10.1126/science.278.5344.1781.

This sort of thing is not entirely speculation as experiments with materials produce these products. However "kick started life" does not mean that it caused the creation of life, instead that a much bigger variety of larger organisms could survive (such as animals).

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