The Earth’s innermost layer is a 400-mile-wide ball of iron, study suggests

(CNN) Scientists have long wondered what lies at the center of the Earth, and the latest research emphasizes a theory that our planet has a distinct ball of iron in its metallic core.

Beneath the outermost crust, mantle, and molten, liquid outer core lies Earth’s solid metallic center — which actually has a hidden layer, or “innermost core,” within, according to a new study.

The monumental find suggests Earth has five major layers instead of four, and offered new details scientists could use to help unlock some of the oldest mysteries about our planet and how it formed.

Geoscientists first suggested that Earth’s core might have an extra, imperceptible layer about 20 years ago, according to a news release. Now, using new data sets collected by measuring the seismic waves of earthquakes as they passed through Earth’s center, scientists have finally discovered the innermost core, the new study said.

Seismic waves are vibrations that travel within or along the Earth’s surface and through its inner layers as a result of earthquakes, volcanoes, or other means.

“In this study, we report for the first time observations of seismic waves originating from powerful earthquakes that travel back and forth from one side of the globe to the other up to five times like a ricochet,” study co-author Dr. Thanh-Son Phạm, a seismologist and postdoctoral researcher at the Research School of Earth Sciences at the Australian National University in Canberra, in an email.

Detection through seismic activity

The reason this layer has not previously been observed in more detail is because its composition is so similar to what lies above it, Pham said. Both this newly discovered center — which the study reports is likely a 400-mile-wide (644-kilometer-wide) ball of metal — and its outer shell are made of an iron-nickel alloy, with trace amounts of other elements.

“Additionally, the transition from the innermost (solid) ball to the outer shell of the inner core (also solid shell) appears gradual rather than sharp,” Pham said. “That’s why we can’t observe it via direct reflections of seismic waves from it.”

Using instruments that detect the vibrational waves, the researchers found that the innermost inner core has a distinct anisotropy, which is a property of matter that allows it to take on different properties depending on the angle from which it is approached. An example of an object that is anisotropic is a piece of wood: It is much easier to chop a piece of wood apart by hitting it in the direction of the grain than against it.

It is that characteristic that distinguishes the innermost core.

When it came to assessing the Earth’s core, the researchers looked at how fast seismic waves traveled through it in different directions, and they found that the innermost inner core changed the speed of these waves differently than the layer above it, the mid-core’s outer core. peel.

Discovering the new layer more than 1,600 kilometers below our feet is significant. The presence of a distinct inner core could give scientists a better understanding of the Earth’s magnetic field, how it has evolved and will continue to do so.

The new discovery also “gives us a glimpse of what might have happened to other planets,” Pham said. “Take Mars as an example. We do not yet understand why (Mars’ magnetic field) ceased to exist in the past.”

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