Earth's Insides Are Cooling Faster Than We Thought, And It Will Mess Things Up

 

Earth formed about 4.5 billion years ago. Ever since then, it's been slowly cooling on the inside.

 

While the surface and atmosphere temperatures fluctuate over the ages (and yes, those external temperatures are currently warming), the melted interior – the beating heart of our planet – has been cooling this entire time.

 

That's not a glib comparison. The rotating, convecting dynamo deep inside Earth is what produces its vast magnetic field, an invisible structure that researchers believe protects our world and allows life to flourish. Furthermore, mantle convection, tectonic activity and volcanism are believed to help sustain life through the equilibrium of global temperatures and the carbon cycle.

 

Because Earth's interior is still cooling, and will continue to do so, this means that ultimately the interior will solidify, and the geological activity will stop, probably turning Earth into a barren rock, akin to Mars or Mercury. New study has revealed that may happen sooner than previously assumed.

 

The key could be a mineral at the borderline between Earth's outer iron-nickel core and the molten fluid lower mantle above it. This boundary mineral is called bridgmanite, and how rapidly it conducts heat will affect how quickly heat seeps through the core and out into the mantle.

 

Estimating that rate is not as simple as testing the conductivity of bridgmanite in ambient atmospheric conditions. Thermal conductivity can fluctuate based on pressure and temperature, which are immensely different deep inside our planet.

 

To overcome this difficulty, a team of researchers led by planetary scientist Motohiko Murakami of ETH Zurich in Switzerland irradiated a single crystal of bridgmanite with pulsed lasers, simultaneously increasing its temperature to 2,440 Kelvin and pressure to 80 gigapascals, close to what we know to be the conditions in the lower mantle – up to 2,630 Kelvin and 127 gigapascals of pressure.

 

"This measurement system let us indicate that the thermal conductivity of bridgmanite is about 1.5 times higher than expected," Murakami said.

 

Consecutively, this means that the heat flow from the core to the mantle is higher than we thought – and, therefore, that the rate at which Earth's interior is cooling is faster than we assumed.

 

 

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The team's research has been published in Earth and Planetary Science Letters.