Washington, Sept 27 : Scientists at the University of Bonn, Germany, have said in a new study that life sustains on Earth because of the planet’s ability to store oxygen in the deep reaches of its mantle.

They said close examination of the mineral majorite, which occurs only at a depth of several hundred kilometres under very high pressures and temperatures, led them to this conclusion.

The team successfully demonstrated that under conditions of high temperature and pressure, the mineral stores oxygen and performs an important function as an oxygen reservoir.
Near the earth's surface the structure breaks down, releasing oxygen, which then binds with hydrogen from the earth's interior to form water.
“Without this mechanism our ‘Blue Planet’ might well be as dry and inhospitable as Mars,” the scientists wrote in their study in the journal Nature.

They said the proverbial ‘solid ground’ under our feet is actually in constant flux.

“At the boundaries between the tectonic plates in what are called the subduction zones this seemingly solid ground is drawn down many hundreds of kilometres into the hot interior. As the material descends it takes with it oxygen, which is bound as iron oxide in the earth's mantle oxygen that derives from the dim distant beginnings of the universe,” the study said.

“Far below the Earth's surface high pressures and temperatures prevail. As the mantle material melts the iron oxide undergoes a chemical metamorphosis in which its oxygen component becomes, in a sense, more reactive. Moreover, it changes its medium of transportation, now being incorporated into the exotic mineral majorite, which only occurs at these depths,” it added.

Lead author Prof. Dr. Christian Ballhaus from the Mineralogical Institute at the Bonn University said, “the higher the pressure, the more oxygen can be stored by majorite”.

He said the majorite could be envisaged as operating like an elevator for oxygen.

But this time it moves in the opposite direction: the mineral rises like warm air above a heater. In fact, the experts talk here about “convection”. However, nearing the earth's surface the pressure in the mantle becomes too weak to maintain the majorite, which then decomposes, he said.

“That's where the stored oxygen is released. Near the surface it is made available for all the oxidation reactions that are essential for life on earth,” said Prof. Ballhaus, whose team is the first to investigate this mechanism under laboratory conditions.

He said the earth constantly exudes hydrogen, which combines with this oxygen to form water, adding, that without this “oxygen elevator” in its mantle, the earth would probably be a barren planet hostile to life.

“According to our findings, planets below a certain size hardly have any chance of forming a stable atmosphere with a high water content. The pressure in their mantle is just not high enough to store sufficient oxygen in the rock and release it again at the surface,” said Arno Rohrbach, doctoral student in the research team at the Mineralogical Institute. (With inputs from ANI)