Two massive geological structures located at the boundary between the Earth’s mantle and core may hold clues about the origins of life on our planet. A study led by Yoshinori Miyazaki, a geodynamicist from Rutgers University, presents a new hypothesis regarding these formations, published in the journal Nature Geoscience.
These continent-sized anomalies, found nearly 1,800 miles beneath the Earth’s surface beneath regions such as Africa and the Pacific Ocean, have perplexed scientists for decades. Their presence is indicated by seismic wave readings, which reveal significant variations in the surrounding rock composition.
“These are not random oddities,” Miyazaki stated. “They are fingerprints of Earth’s earliest history.” Understanding these structures could illuminate how Earth formed and why it became a hospitable environment for life.
Current theories suggest that the early Earth developed a mantle from a vast magma ocean billions of years ago. Over time, the materials within this ocean became separated, similar to how “frozen juice separates into sugary concentrate and watery ice.” Despite this explanation, evidence supporting it has been elusive. Instead of uniform layers, researchers have identified large irregular formations known as “large-low shear velocity provinces” and “ultra-low velocity zones,” which are characteristic of the Earth’s deep mantle.
Miyazaki explained that these observations presented a challenge. “If we start from the magma ocean and do the calculations, we don’t get what we see in Earth’s mantle today. Something was missing.”
The research team modeled ancient conditions, discovering that a slow seepage of silicon and magnesium from the Earth’s core may have “contaminated” the basal magma ocean. This process could have prevented the magma from solidifying uniformly, resulting in the uneven structure observed today. “If you add the core component, it could explain what we see right now,” Miyazaki noted.
This interaction between the core and mantle may have also facilitated the cooling of the Earth, promoting volcanic activity and influencing atmospheric formation. Such insights could help explain why Earth, unlike Venus and Mars, is capable of supporting life.
“Earth has water, life, and a relatively stable atmosphere,” Miyazaki elaborated. “In contrast, Venus’ atmosphere is 100 times thicker than Earth’s, mainly composed of carbon dioxide, while Mars has a very thin atmosphere.”
Understanding the dynamics of a planet’s interior—how it cools and how its layers evolve—could be crucial to comprehending these differences. Miyazaki expressed optimism about the future of this research, suggesting that while they have only “very few clues,” the findings could provide greater certainty about how Earth evolved and why it remains unique among the planets.
As scientists continue to explore these profound geological mysteries, the research underscores the complex interplay between Earth’s internal structures and the conditions that fostered life.
