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Huge Stockpile of Oxygen Found Deep Inside Earth

2007-10-03 03:46:01

Jeanna Bryner

LiveScience Staff

LiveScience.comTue Oct 2, 4:35 PM ET

A mineral that acts like a sponge beneath Earth's surface stores more oxygen

than expected, keeping our planet from becoming dry and inhospitable like Mars.

The key to the abundant oxygen storage is the mineral majorite, which exists

deep below Earth's surface in the mantle. Without the oxygen stockpile, Earth

would probably be a barren planet hostile to life, authors of a study suggest

in the Sept. 27 issue of the journal Nature.

The researchers examined majorite in the lab under conditions mimicking the

Earth's deep interior and also near the planet's surface. The results showed

that under deep-Earth conditions of high temperature and pressure, majorite

stores large amounts of oxygen. When the temperature and pressure were

decreased, as occurs near Earth's surface, the majorite decomposed and released

the oxygen.

"The Earth's upper mantle can store, therefore, much more oxygen than

previously expected," said lead author Arno Rohrbach, a doctoral student at the

University of Bonn's Mineralogical Institute in Germany.

In nature, the deep stores of oxygen (in the form of majorite) ride convection

currents up toward Earth's surface. Along the way, the pressure and temperature

decrease, and at some point majorite breaks down.

"That's where the stored oxygen is released," said study team member Christian

Ballhaus of Bonn's Mineralogical Institute. "Near the surface it is made

available for all the oxidation reactions that are essential for life on

Earth."

This process could also be responsible for some of Earth's water, Rohrbach

said. Unlocked oxygen can bind with hydrogen that constantly seeps from Earth's

interior to form water, making for a water-rich atmosphere. "Primordial

hydrogen, trapped during the accretion/formation of planet Earth, is degassing

constantly from the Earth's interior," Rohrbach told LiveScience.

Once the water is made, Earth's magnetic field helps to keep it in place. "The

magnetic field prevents the atmosphere from being 'blown away' by solar winds,"

Rohrbach said.

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Phenomena Original Story: Huge Stockpile of Oxygen Found Deep Inside Earth