Why Mysterious Structures in Earth's Mantle Hold Clues to Life's Origin
For decades, scientists have grappled with two colossal, enigmatic structures buried deep within Earth, so unusual that they challenge our understanding of planetary evolution. Now, a groundbreaking study published in Nature Geoscience by Rutgers geodynamicist Yoshinori Miyazaki and his team offers a compelling explanation for these anomalies and their role in Earth's ability to support life.
Deep beneath the surface, nearly 1,800 miles down, lie two peculiar phenomena: Large Low-Shear Velocity Provinces (LLSVPs) and Ultra-Low Velocity Zones (ULVZs). LLSVPs are continent-sized blobs of dense, molten rock, one beneath Africa and the other under the Pacific Ocean. ULVZs, on the other hand, are thin, molten patches clinging to the core like lava flows. These structures significantly slow down seismic waves, indicating a unique composition that sets them apart from the rest of the mantle.
Miyazaki, an assistant professor at Rutgers, emphasizes the significance of these structures: "They are not random anomalies but fingerprints of Earth's ancient history. Understanding their origin can reveal how our planet formed and why it became habitable."
Unraveling the Mantle Mystery
Billions of years ago, Earth was a molten mass of magma, according to Miyazaki. As it cooled, scientists expected the mantle to form distinct chemical layers, similar to the separation of juice and ice in a frozen drink. However, seismic studies have revealed no such clear layering. Instead, LLSVPs and ULVZs form irregular piles at the base of the planet, contradicting the expected layering.
"That contradiction was our starting point," Miyazaki explains. "When we start from the magma ocean and perform calculations, we don't get the mantle we see today. Something was missing."
Miyazaki and his collaborators concluded that the missing piece is the core itself. Their model suggests that over billions of years, elements like silicon and magnesium leaked from the core into the mantle, mixing with it and preventing strong chemical layering. This infusion could explain the unusual composition of LLSVPs and ULVZs, which may be solidified remnants of what the scientists call a "basal magma ocean" contaminated by core material.
"We proposed that it might be coming from material leaking out from the core," Miyazaki says. "Adding the core component could explain what we observe in the mantle today."
Implications for Earth's Habitable Nature
The study's findings go beyond deep-Earth chemistry, Miyazaki notes. Core-mantle interactions may have influenced Earth's cooling, volcanic activity, and even atmospheric evolution. This could help explain why Earth has oceans and life, while Venus is a scorching greenhouse and Mars is a frozen desert.
"Earth has water, life, and a relatively stable atmosphere," Miyazaki points out. "Venus' atmosphere is 100 times thicker than Earth's, mostly composed of carbon dioxide, and Mars has a very thin atmosphere. We don't fully understand why, but what happens inside a planet, how it cools, and how its layers evolve, could be crucial to the answer."
By integrating seismic data, mineral physics, and geodynamic modeling, the study recasts LLSVPs and ULVZs as vital clues to Earth's formative processes. These structures may even feed volcanic hotspots like Hawaii and Iceland, linking the deep Earth to its surface.
"This work exemplifies how combining planetary science, geodynamics, and mineral physics can solve some of Earth's oldest mysteries," says Jie Deng of Princeton University, a co-author of the study. "The idea that the deep mantle could still carry the chemical memory of early core-mantle interactions opens new avenues for understanding Earth's unique evolution."
As researchers continue to uncover more evidence, they are filling in gaps in Earth's early history, transforming scattered clues into a clearer picture of its evolution. Miyazaki concludes, "Even with limited clues, we're building a coherent story. This study provides more certainty about Earth's evolution and why it's so special."
For more information, see: Jie Deng et al. (2025). Deep mantle heterogeneities formed through a basal magma ocean contaminated by core exsolution. Nature Geoscience. DOI: 10.1038/s41561-025-01797-y
