Since its formation, the Earth has been releasing vast amounts of heat from deep inside Earth’s interior to the surface, which primarily drives mantle convection and a number of tectonic activities. The core-mantle boundary has played an essential role in this heat transfer process.
This is the boundary where the hot molten core is in direct contact with solid-state mantle minerals and helps transfer the thermal energies of the core to the overlying mantle.
In a study, scientists looked at how well this boundary mineral, called bridgmanite, could conduct heat from the core to the surface.
They found that the boundary was able to dispense so much heat that scientists now believe that the earth is losing heat from its interior at a much faster rate than previously expected.
When the Earth first formed about 4.5 billion years ago, the earth was covered by a deep ocean of magma, which then gradually cooled to form the crust we know today.
Because the earth’s interior is still giving out heat, it will eventually cool down completely, turning the planet into a barren wasteland like Mars and Mercury.
To recreate the effects of intense heat and pressure that the boundary faces between the mantle and the core, a team of scientists irradiated a single crystal of bridgmanite with pulsed lasers.
This simultaneously increases its temperature to 2,440 Kelvin and pressure to 80 gigapascals, which is close to what we know to be the conditions in the lower mantle – up to 2,630 Kelvin and 127 gigapascals of pressure.
Planetary scientist Motohiko Murakami, who led the study said: “This measurement system let us show that the thermal conductivity of bridgmanite is about 1.5 times higher than assumed.”
Research suggests that this natural process of cooling for the earth’s core could be speeding up.
When cooled down, bridgmanite turns into the mineral post-perovskite.
However as the amount of post-perovskite increases in the core-mantle boundary, the cooling of the mantle might indeed accelerate even further.
The researchers estimate that this mineral conducts heat even more efficiently than bridgmanite.
Mr Murakami said: “Our results could give us a new perspective on the evolution of the Earth’s dynamics.
“They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected.”
However, scientists are still unable to figure out when the planet would cool down and become geologically inert.
It is difficult to compare the Earth to Mars, as the Red Planet is significantly smaller than the earth, and hence cooling faster.
Mr Murakami said: “We still don’t know enough about these kinds of events to pin down their timing.”