Having studied how seismic waves move through the Earth's core, geologists have come to the conclusion that it should contain about 0.3-2% carbon. This makes the core the largest carbon reservoir on the planet, scientists say. The research was published in the scientific journal Communications Earth & Environment.
"We know that the core of the Earth is mostly made of iron, but the density of the latter is noticeably higher than that of the core. This indicates a significant proportion of light elements, one of which may be carbon. We found out how large its reserves can be," - said one of the authors of the study, associate professor at the Florida State Institute, Minak Mukherjee.
The core of the Earth consists of two layers: a solid metal core and a surrounding liquid layer of molten iron and nickel. This liquid is constantly moving, just like water spins in a boiling kettle. The result is a magnetic field that protects the Earth from cosmic rays, solar flares and other dangerous cosmic phenomena.
Geologists have long been interested in how this movement occurs, and what processes inside the core lead to periodic flips of the Earth's magnetic poles, as well as to weakening and strengthening of the magnetic field. To answer this question, it is extremely important to know the exact composition of the liquid and solid core, since the presence of small impurities of other elements can significantly change the nature of the flow of flows in the core.
Mukherjee and his colleagues found that a significant proportion of these impurities are carbon, which, presumably, fell into the lower layers of the planet's interior in the first moments of the life of the solar system. Scientists came to this conclusion when creating a computer model of the Earth's core and mantle, capable of reproducing the appearance of the deepest sources of seismic waves.
The first observations of such fluctuations, which were carried out back in the early 1990s, indicated that the Earth's liquid core is about 3% composed of various impurities. Their composition remained a mystery to scientists, since no potential candidate for this role, including oxygen, sulfur, silicon and carbon, could explain all the oddities in the behavior of deep sources of seismic waves.
For the first time, American geologists were able to resolve these contradictions. This became possible due to the fact that they calculated in detail how carbon melts in iron behave under a wide range of pressures and temperatures. Mukherjee and his colleagues obtained similar data for nitrogen, silicon, oxygen, sulfur and hydrogen.
Based on these calculations, the researchers created a set of computer models of the Earth's interior, which described in detail the nature of the circulation of matter inside the liquid core. With their help, geologists calculated how deep seismic waves would interact with them, and compared the results of these calculations with real observations.
It turned out that all their features were reproduced by those models of the liquid part of the Earth's core, which included very large reserves of carbon, about 0.3-2% of its total mass, as well as significant amounts of oxygen. This means that almost 95% of the mass of Earth's carbon is concentrated in the center of the planet, making the core the largest reservoir of this element on our planet.
How such large amounts of carbon got there, geologists cannot yet say. They suggest that carbon has been in the center of the Earth since the very first phases of its formation. If this is true, scientists will have to rethink current ideas about how carbon behaved during the formation of the planet, Mukherjee and his colleagues concluded.