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Scientists finally have solid evidence: the nucleus of the Earth is solid, if it is a little spongy, according to a new study.
The theory that the core of the Earth is solid dates back to 1936 and was proposed by seismologist Inge Lehmann when she analyzed the 1929 earthquake data again in Murchison, New Zealand. But until recently, there was no way to prove it.
Then the team of Australian National University hit on the idea of using earthquakes again. They decided to study the echoes of earthquakes using a technique used by researchers to measure Antarctic ice sheets for decades.
Dr. Hrvoje Tkalčić, researcher Than-Son Phạm and their colleagues examined the similarities recorded by pairs of receivers after major earthquakes. The team has detected "J waves" that can only cross solid objects deep in the Earth.
"By using a global network of stations, we take each pair of receivers and each major earthquake – that is, many combinations – and we measure the similarity between the seismograms," Tkalčić told the magazine. Newsweek. This is called cross-correlation, or measure of similarity. From these similarities, we build a global correlogram – a kind of fingerprint of the Earth. "
What this fingerprint has shown is that there is solid material in the nucleus of the Earth. However, it is also much sweeter than expected by scientists.
"It turns out that – if our results are correct – the inner core shares similar elastic properties with gold and platinum," Tkalčić said. "The inner core is like a time capsule; if we understand this, we will understand how the planet was formed and how it evolves. "
The study solves one of the mysteries of the Earth's core, said Tkalčić and Pham, but there is still research to be done before scientists can understand the center of our planet.
"For example, we do not yet know what is the exact temperature of the inner core, what is the age of the inner core, or how fast it solidifies, but with these new advances in global seismology, we are getting there slowly, "Tkalčić said.
The study was published in the journal Science.
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