The center of the earth is leaking helium

L'hélium-3 dégazé au niveau des dorsales proviendrait du noyau externe de la Terre. © JohanSwanepoel, Fotolia

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I ‘Radiation Is one Chemical components The formation of terrestrial rocks and a part derived from the time when our planet began its formation. Helium, like other volatile elements, actually exists Nebula In our appearance The sun And other planets The Solar System. The study of these elements within terrestrial rocks, especially their size, allows us to go back to the composition of the ancient nebula and restore the history of the formation of the Earth.

A primordial gas stored in the depths of the earth

Chemical analysis of the rocks shows that these volatile elements are present in the earth’s interior: Code And potentially, important. If our knowledge of the composition of the ancient coat began to be more precise, its composition The center of the earth Since access to the deepest parts of the world is impossible, it is very approximate.

However, helium-3 (3He) during the process of creating the ocean surface, constantly escaping from the earth’s interior at the level of the ridges. However, unlike the most common helium-4 (4He) It is found in abundance on Earth – and it is one of the products of the decay of radioactive elements. Uranium And Thorium -, helium-3 is a Gas Very rare Adi, Created after the Big Bang. It is part of the nebula that gave birth to the sun and the earth.

Despite the various stages in the formation of the earth, they contributed greatly Gas removal Formation of essential volatile elements, especially during intense meteor bombing நிலா Or Solidification of the magma ocean, It appears that the Earth was able to hide the helium-3 reservoir in its deeper layers. But exactly where it is located and what its size is 3Is he the rest?

External core, helium-3 reservoir?

The presence of helium-3 in basalts produced on sea ridges, however Hot spotsThis indicates that the reservoir is located at depth and that this chemical element is definitely carried to the surface Via The process of mantle convection. Helium-3 is rarely recycled once released to the surface: only a small amount returns to the depths of the mantle through the zones. Submission. Almost all of this gas is actually releasedAtmosphere, And then into space. Obtained 4.56 billion years ago, the deep reservoir of helium-3 is unfilled.

In a recent study, scientists became interested in the nature of this reservoir. Their basic premise is that the center of the earth represents a good storage area for this primitive gas. At a depth of more than 2,800 km, the center is, in fact, the deepest part of the Earth, and therefore the most protected zone from meteorite impacts involved in the removal of gas from the ancient mantle.

Furthermore, the rocks of the center do not directly participate in plate tectonics rotations affecting the surface layers. The position of the outer center Its formation has changed very little since and is largely in shape Liquid. The outdoor center therefore represents a favorable location for storing noble gasesHydrogen Or helium. However, it is not yet understood how these components can be integrated in a consistent way.

Continuous leakage of helium

To control the location of the outer center of the helium-3 reservoir, two scientists at the University of New Mexico in Alberg (USA) performed calculations to measure helium-3 emissions and to understand the interactions between the center and the surface. History of the Earth.

Results, published Geochemistry, geophysics, geospatial systems, The dissolution of the oldest atmosphere resulting from the nebula would have allowed one or several million tons of 3He to accumulate in the nucleus formed 4.5 billion years ago. Based on core interaction and outcasing models Via Process ConvectionResearchers estimate that size 3In the mantle he is currently evolving towards a steady state in which the surface leakage is compensated for by continuous enrichment from the remaining helium-3 storage center.

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