A recent study suggests that a thick layer of diamonds may exist hundreds of miles underneath the surface of Mercury, according to a report in Live Science. Yanhao Lin, a staff scientist at the Center for High-Pressure Science and Technology Advanced Research in Beijing and co-author of the study said that Mercury’s extremely high carbon content “made me realize that something special probably happened within its interior.” The first planet of our solar system has a magnetic field, however, it is much weaker than Earth. Further, NASA’s Messenger spacecraft discovered anomalously black areas on Mercury’s surface that it recognized as graphite, a type of carbon.
The results of the study were published in the journal Nature Communications and could provide light on the composition and unusual magnetic field of the planet.
Scientists believe that the planet most likely formed from the cooling of a hot lava ocean, similar to how other terrestrial planets developed. This ocean was probably rich in silicate and carbon in Mercury's case. The planet's outer crust and middle mantle formed from the residual magma crystallizing while metals first coagulated within it to form a central core.
For many years, scientists believed that the temperature and pressure in the mantle were exactly right for carbon to form graphite, which floats to the surface because it is lighter than the mantle. However, a 2019 study revealed that the mantle of Mercury might be 50 kilometers (80 miles) deeper than previously thought. This would significantly increase the temperature and pressure at the mantle-core boundary, resulting in circumstances where the carbon could crystallize into a diamond.
A team of Belgian and Chinese researchers prepared chemical soups using carbon, silica, and iron to look at this possibility. These mixes, which resemble several types of meteorites in composition, are believed to resemble the magma ocean of the infant Mercury. In addition, the researchers added different concentrations of iron sulfide to these soups. Based on the sulfur-rich surface of Mercury today, they understood that the magma ocean was likewise rich in sulfur.
The scientists crushed the chemical mixes at 7 gigapascals, or 70,000 times the pressure of Earth's atmosphere at sea level, using a multiple-anvil press. These harsh circumstances mirror those found deep within Mercury. In addition to recreating the physical conditions under which graphite or diamond would be stable, the researchers employed computer models to obtain more accurate measurements of the temperature and pressure near Mercury's core-mantle border. Mr Lin claims that these computer simulations provide information regarding the basic compositions of the planet's interiors.
According to the investigations, minerals like olivine most likely developed in the mantle. However, the group also found that the chemical mixture only solidified at substantially higher temperatures when sulfur was added. Diamond formation is more likely to occur under such circumstances. Further, the team's computer models suggested that diamonds might have formed during the solidification of Mercury's inner core under these altered circumstances. Then, it floated up to the core-mantle barrier because it was less dense than the core. According to the estimates, if diamonds are present, they form a layer that is typically roughly 15 km (9 miles) thick.
However, it is not feasible to mine these diamonds. In addition to the extremely high temperatures on the planet, the diamonds are located almost 485 km below the surface, making extraction impossible. According to Mr Lin, the diamonds might aid in the transfer of heat between the mantle and the core, resulting in temperature differentials and the swirling of liquid iron, which would produce a magnetic field.