The Earth’s molten interior is cooling faster than expected, which could turn the planet into a cold, inactive world similar to neighboring Mercury and Mars sooner than previously thought, researchers have warned.
The study, published in the Earth and Planetary Science Letters journal, examined how well bridgmanite – the primary mineral found at the boundary between the planet’s core and mantle layers – conducts heat from the hot, molten core to the surface.
Researchers irradiated a bridgmanite crystal with pulsed lasers on a diamond anvil press to simulate the effects of intense heat and pressure at the boundary. They found that the rate at which the mineral conducted heat was “about 1.5 times higher than assumed.”
The findings mean that the cooling of the Earth’s core is speeding up, and it is “becoming inactive much faster than expected.”
The rapid cooling could in turn lead to an earlier slowing-down of processes like plate tectonics, which are related to the movements of large underground slabs composed of the crust and outer mantle layer, and volcanic activity.
This heat exchange from the planet’s core helps generate the Earth’s magnetic field, which is understood to be protecting the planet’s atmosphere from solar radiation and allowing life to thrive.
The rapid cooling may accelerate even more in the future, since cooled bridgmanite transforms into a mineral known as post-perovskite, which conducts heat even more quickly.
“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,” said ETH Zurich Earth scientist Motohiko Murakami, who led the study.
However, it remains unclear exactly how long it will take for thermal convection currents within the mantle to stop entirely. Murakami said that not enough is known about such events to “pin down their timing.”
Besides a better understanding of mantle convection in “spatial and temporal terms,” Murakami noted that any predictive timeline would also need to account for how mantle dynamics are affected by the decay of radioactive elements in the core, which is a key source of the Earth’s internal heat.
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