Giant ‘Doughnut’ Structure Discovered in Earth’s Molten Core Reveals Hidden Secrets

Scientists have made a groundbreaking discovery at the center of the Earth, uncovering a ring-like structure within the molten metal pool known as the outer core. This finding, published in the journal Science Advances, reveals a doughnut-shaped region within the outer core, parallel to the equator—a discovery that could provide new insights into the dynamics of Earth’s magnetic field.

Journey to the Core: Seismic Waves as the Key

Due to technological limitations, scientists cannot physically reach the Earth’s core. Instead, they rely on seismic waves generated by large earthquakes, which travel through the Earth and provide crucial information about its inner structure. The research team, led by Australian National University geophysicist Prof Hrvoje Tkalčić, analyzed these seismic waves to better understand the outer core’s composition.

“By understanding the geometry of the paths of the waves and how they traverse the outer core’s volume, we reconstructed their travel times through the Earth,” Tkalčić explained. The study revealed that seismic waves slow down significantly in a specific section near the ceiling of the outer core, just before the mantle begins.

“We realised that seismic waves slow down in the zone that mathematically is called a torus,” Tkalčić added. To most people, this torus resembles a doughnut—a term that captures the unique shape of this newly identified region within the Earth.

The Outer Core’s Role in Protecting Life on Earth

Understanding the outer core is crucial because it plays a vital role in maintaining life on Earth. The outer core, composed mainly of molten iron and nickel, generates and sustains the Earth’s magnetic field through currents that act like a “giant dynamo.” This magnetic field shields the planet from harmful solar radiation and charged particles from the sun, making it essential for the survival of life on the surface.

“The outer core is critical to the survival of life at the surface,” Tkalčić emphasized. Despite its importance, many aspects of this region remain enigmatic. Tkalčić noted, “It’s fair to say that we understand the surfaces of other planets in more detail than our own planet’s interior.”

A Planet Within a Planet: The Inner Workings of Earth’s Core

Earth’s interior is structured like a planetary system within itself, comprising a solid inner core surrounded by the liquid outer core and then the mantle. Tkalčić described the overall size of the core as being slightly larger than Mars, highlighting its immense scale: “We can think of it as a planet within our own planet.”

Though the exact thickness of the doughnut-shaped structure remains unknown, the researchers inferred it extends several hundred kilometers beneath the core-mantle boundary. Its buoyancy suggests it contains lighter chemical elements, such as silicon, sulfur, oxygen, hydrogen, or carbon, which could provide further insights into the complex dynamics within the core.

Unsolved Mysteries: What Lies Within the Earth’s Outer Core?

Despite this breakthrough, many questions about the outer core remain unanswered. Dr. Xiaolong Ma, a co-author of the study, remarked that the discovery of this new structure lifts a veil on the workings of Earth’s magnetic field but acknowledged that there are still “mysteries about the Earth’s outer core that are yet to be solved.”

Prof Tkalčić echoed this sentiment, noting the limitations of current knowledge: “What makes this field really fascinating is that pretty much everything we do know is an inference based on the data that we have on the surface.” As researchers continue to explore these hidden depths, each new finding brings them closer to unraveling the secrets of our planet’s dynamic core.