Earth's Insides Are Cooling Faster Than We Thought, And It Will Mess Things Up
Earth formed 4.5 billion years or so ago. Ever since then, it's been slowly cooling on the inside.
While the surface and atmosphere temperatures fluctuate over the eons (and yes, those external temperatures are currently warming), the molten interior – the beating heart of our planet – has been cooling this entire time.
That's not a glib metaphor. The rotating, convecting dynamo deep inside Earth is what generates its vast magnetic field, an invisible structure that scientists believe protects our world and allows life to thrive. In addition, mantle convection, tectonic activity, and volcanism are thought to help sustain life through the stabilization of global temperatures and the carbon cycle.
Because Earth's interior is still cooling and will continue to do so, this means that eventually the interior will solidify, and the geological activity will cease, possibly turning Earth into a barren rock, akin to Mars or Mercury. New research has revealed that may happen sooner than previously thought.
The key could be a mineral at the boundary between Earth's outer iron-nickel core and the molten fluid lower mantle above it. This boundary mineral is called bridgmanite, and how quickly it conducts heat will influence how quickly heat seeps through the core and out into the mantle.
Determining that rate is not as simple as testing the conductivity of bridgmanite in ambient atmospheric conditions. Thermal conductivity can vary based on pressure and temperature, which are vastly different deep inside our planet.