At a depth of 3,000 kilometers beneath our feet hides a ball of iron and nickel somewhat more massive than Pluto, which is far from resembling the center of the Earth imagined by Jules Verne. It is the nucleus of our planet, inaccessible, at least for the moment, where temperatures could reach 6,000 degrees Celsius.
Scientists have known for decades that the nucleus is solid, but until now there has been no direct evidence to confirm this. Now, researchers from the Australian National University (ANU) claim to have the proofs. The team detected cut-off waves, or “J waves,” in the inner core, a type of wave that can only travel through solid objects.
“We found that the inner core is rock-solid, but also softer than previously thought,” says Hrvoje Tkalcic, co-author of the study. If its results, published in the journal Science, are correct, the Earth’s core shares some elastic properties such as gold and platinum.
The cutoff waves of the Earth’s core are so small and weak that they cannot be directly observed. In fact, detecting them has been considered the “Holy Grail” of global seismology since scientists first predicted that the inner core was solid in the 1930s and 1940s.
Scientists confirmed the Earth’s core is solid but elastic as gold or platinum
“We have discarded the first three hours of the seismogram and observed between three and ten hours after a major earthquake occurs. We wanted to get rid of the big signals,” Tkalcic said.
With all that data from thousands of pairs of receivers, they were able to reconstruct a kind of fingerprint of the planet that demonstrates the existence of “J waves” and infer their velocity in the inner core.
Tkalcic believes that the Earth’s nucleus, “is like a time capsule. If we understand it, we will understand how the planet was formed and how it evolves,” he says. In his opinion, the technique employed can help unravel other mysteries of the Earth’s center.
“For example, we still do not know the exact temperature, its exact age or the speed with which it solidifies, but with these new advances in global seismology, we are arriving little by little”, he indicates. He adds that “understanding the Earth’s core has direct consequences for the generation and maintenance of the geomagnetic field, and without that geomagnetic field, there would be no life on the Earth.”