Perhaps we are not aware of it, but the core of our planet is burning at excessively high temperatures right now. The issue is that since its formation about 4.5 billion years ago, the Earth has been cooling slowly. This fact was already known to geology experts; however, a new study suggests that the Earth’s core is cooling faster than expected.
The Earth’s core is more than just hot metals; it is actually the planet’s beating heart that keeps it alive. Thanks to it, the protective shield we know as the magnetic field rises, shielding us from solar radiation. Additionally, it is also responsible for the complex systems of volcanoes and seismic activity that release energy and stabilize global temperatures and the carbon cycle. In other words, without a hot core, this biological bubble would simply die slowly.
To determine the rate at which the Earth’s core is cooling, researchers from the University of Zurich in Switzerland analyzed a type of mineral found between the boundary of the outer core of iron and nickel, and the lower mantle. This type of mineral is known as bridgmanite and is crucial because the speed at which it loses heat is equivalent to the heat that the core releases to the lower mantle.
The transition to a barren rock
Determining the speed is not simple, as it requires a simulation of the thermal conductivity of bridgmanite under similar pressure and temperature conditions to those of the Earth’s core. To overcome this difficulty, researchers used pulsed lasers to overheat the bridgmanite to over 2000°C and reach a pressure of 80 gigapascals.
“This measurement system allows us to demonstrate that the thermal conductivity of bridgmanite is approximately 1.5 times higher than previously assumed,” says Murakami, co-author of the research.
This means that the heat flow from the core is 1.5 times faster than previously thought. This, in turn, implies that the core releases heat to the lower mantle 1.5 times more rapidly. Additionally, they also conclude that the process could be accelerating because when bridgmanite cools, it produces another type of mineral called post-perovskite, which is even more thermally conductive. In that sense, the rate of heat loss would increase even further.
Of course, we are not talking about a process that is fast in terms of human time scales. Rather, it is a cooling process that would take millions of years, but it is still relevant to humans because it helps to understand how other planets ended up cooling down and becoming barren rocks, like Mars or Venus, a fate that seems to also await Earth.
References: Murakami, M., Goncharov, A., Miyajima, N., Yamazaki, D., Holtgrewe, N. (2022). Radiative thermal conductivity of single-crystal bridgmanite at the core-mantle boundary with implications for thermal evolution of the Earth. Earth and Planetary Science Letters. DOI
This story was written in Spanish by Ecoosfera
