Possible remnants of early Earth discovered sitting near planet's core

Possible remnants of early Earth sitting near the world’s core could be left over from a collision with an ancient planet 4.5 billion years ago, a new study suggests.

Researchers at the University of Utah have discovered layers of matter deep within the Earth’s mantle which they say could help to explain how the world developed.

Surya Pachhai, who worked on the study, said the layering could have been created after a planet roughly the size of Mars crashed into Earth about 4.5 billion years ago.

The hypothesised collision may have thrown debris into Earth’s orbit which later formed the moon as well as raising the temperature of the Earth significantly.

“As a result, a large body of molten material, known as a magma ocean, formed,” Pachhai said.

The “magma ocean” would have eventually cooled, with dense materials sinking and piling on top of one another on the bottom of the mantle, according to the study.

The layers discovered in the study could show areas where materials have still not mixed together after billions of years of convection currents – movement caused by the heat of the Earth’s core – within the mantle, scientists said.

The researchers studied ultra-low velocity zones – the patches of the Earth’s core-mantle boundary where the layering was detected – beneath the Coral Sea, between Australia and New Zealand.

This location offered a clearer picture of the zones because it experiences frequent earthquakes, which allow scientists to measure seismic waves as they radiate deeper into the Earth’s surface.

The measurements can then be used to examine how the waves move within each layer of the surface, revealing information about the density and make-up of the planet’s structure.

“The physical properties of ultra-low velocity zones are linked to their origin, which in turn provides important information about the thermal and chemical status, evolution and dynamics of Earth’s lowermost mantle — an essential part of mantle convection that drives plate tectonics,” Pachhai said.

“The primary and most surprising finding is that the ultra-low velocity zones are not homogenous but contain strong heterogeneities (structural and compositional variations) within them.

“This finding changes our view on the origin and dynamics of ultra-low velocity zones.

“We found that this type of ultra-low velocity zone can be explained by chemical heterogeneities created at the very beginning of the Earth’s history and that they are still not well mixed after 4.5 billion years of mantle convection.”