More than 5,000 kilometers beneath us, Earths solid metal inner core wasnt discovereduntil 1936.
Almost a century later, were still struggling to answer basic questions about when and how it first formed.
These arent easy puzzles to solve.
Combining these disciplines, scientists have delivered an important clue about whats happening miles beneath our feet.
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The loss of this heat, and heating by ongoing radioactive decay, have since driven our planets evolution.
Meanwhile, cooling within Earths deep interior helps powerplate tectonics, which shape the surface of our planet.
In the 1990s,scientistsrealised that the speed of seismic waves travelling through the inner core varied unexpectedly.
This suggested that something asymmetrical was happening in the inner core.
Specifically, the eastern and western halves of the inner core showed different seismic wavespeed variations.
Dating the core
So does this approach help us understand how old the inner core might be?
This new work presents a powerful new model of the inner core.
And does our uneven inner core make the Earth unusual?
It turns out that many planetary bodies have two halves which are somehow different to each other.
OnMars, the surface of the northern half is lower-lying while the southern half is more mountainous.
TheMoonsnear-side crust is chemically different to the far-side one.
