Earth is cooling faster than expected. Geologists at ETH Zurich are now able to determine this using the thermal conductivity of Earth’s mantle. According to this, the core transfers about 50% more heat to the mantle than before.

Hot core is a basic requirement for life on Earth

Life on earth is also possible because there is life inside this planet. Not only does the Earth’s hot core trigger plate shifts, mountains and volcanoes can also be traced to this core. In addition, the valuable protective factor of the Earth’s magnetic field should not be forgotten. It is also produced by currents in the Earth’s interior. Layers of lava containing the metal flow together in such a way that the planet becomes a giant dynamo and can block dangerous radiation from space with a strong magnetic field. According to some researchers, the complete cooling of the Earth’s core could be the same on our home planet as on Mars.

The fact that it may one day come like this is also due to the natural thermal conductivity of the coat. The mineral bridgmanite is found largely in the transition zone between the mantle and the Earth’s core. This viscous layer of rock is constantly associated with lava composed of iron and nickel, but heated by about 1000 °C. “Because of its sharp temperature gradient, it has the greatest thermal limit on Earth, which raises the question of how quickly Earth loses heat and how long it can remain dynamically active,” say the researchers at ETH Zurich. . In fact, the general heat loss of the entire planet should be based on this limit.

Researchers had to mimic conditions in Earth’s core

So far, a significant problem has arisen in measuring the thermal conductivity of bridgmanite. To be able to determine how much heat the mineral absorbs and re-releases, scientists had to simulate the process in Earth’s interior and also take into account similar conditions in terms of pressure and temperature. Swiss researchers are now able to set up exactly such a system by producing monocrystalline crystals from bridgmanite under high pressure and heat and subjected to pressures of 80 gigapascals using a diamond anvil cell. A laser can then be used to heat the crystal to a temperature of about 2200 °C.

The measurement can eventually be done using a spectroscope. With this instrument, outgoing radiation can be measured and conclusions can be drawn about the crystal lattice, heat conduction and heat.

About 5.3 Watts per meter and Kelvin (W/mK) is passed by the mineral. The researchers estimate that the total thermal conductivity should be around 15.2 W/mK. The new results are 1.5 times higher than previous geophysical estimates.

“Our results may give us a new perspective on the evolution of Earth’s dynamics,” says geologist Motohiko Murakami. “They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and deactivating much faster than expected.”

However, scientists have not been able to draw any conclusion about how long the Earth will remain cold. “With the current state of knowledge, it is not possible to limit the timing of such events,” the geologist says. This will require further information about the process of radioactive decay of elements in Earth’s core and the process of mantle collection.

Link to study: https://www.sciencedirect.com/science/article/pii/S0012821X21005859

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