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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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