Two massive structures located at the boundary between the Earth’s mantle and core may hold answers to the origins of life on our planet. In a groundbreaking study published in the journal Nature Geoscience, a team of researchers led by Yoshinori Miyazaki from Rutgers University proposes that these formations are not mere anomalies but critical components of Earth’s early history.
These continent-sized masses, situated nearly 1,800 miles beneath the surface beneath Africa and the Pacific Ocean, have perplexed scientists for decades. They are detectable through seismic wave readings, which reveal significant variations in the composition of surrounding rocks. According to Miyazaki, “These are not random oddities. They are fingerprints of Earth’s earliest history.”
Current scientific theories suggest that the early Earth formed a mantle billions of years ago from a vast magma ocean, which gradually separated materials of varying concentrations. This process has been likened to “frozen juice separating into sugary concentrate and watery ice.” Despite this analogy, finding concrete evidence to support the theory has proven challenging.
The research team found that instead of the anticipated even layers, the mantle is characterized by irregular lumps known as “large-low shear velocity provinces” and “ultra-low velocity zones.” These structures significantly slow seismic waves, creating a contradiction to existing models. “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,” Miyazaki stated.
To explore this discrepancy, Miyazaki and his colleagues modeled conditions from billions of years ago. They proposed that a gradual seepage of silicon and magnesium from the Earth’s core might have contaminated the basal magma ocean. This contamination could have prevented portions of the ocean from solidifying, leading to the uneven mantle composition observed today. “What we proposed was that it might be coming from material leaking out from the core,” Miyazaki explained. “If you add the core component, it could explain what we see right now.”
This process could have contributed to the Earth cooling sufficiently to allow volcanic activity, which in turn influenced the formation of the planet’s atmosphere. The findings also shed light on why Earth has managed to support life, while neighboring planets such as Venus and Mars evolved into inhospitable environments. “Earth has water, life, and a relatively stable atmosphere,” Miyazaki noted, contrasting it with Venus, which has an atmosphere 100 times thicker than Earth’s and is predominantly composed of carbon dioxide.
Understanding the internal processes that govern a planet’s cooling and layer evolution could be crucial in explaining the conditions that foster life. “We don’t fully understand why that is,” Miyazaki remarked. “But what happens inside a planet, that is, how it cools, how its layers evolve, could be a big part of the answer.”
While this research represents only the beginning of a theory that might clarify the evolution of Earth, it emphasizes the need for further investigation. Miyazaki concluded that the findings provide a “little more certainty about how Earth evolved, and why it’s so special,” despite the challenges that lie ahead in gathering additional evidence.
