A new study published in the journal Nature claims that Mercury hides a layer up to 18 kilometers thick (11 miles) made up of diamonds. Although the mineral could not be extracted because it is 300 kilometers below its surface, it is an important discovery about the formation of planetary layers and opens the door for other terrestrial planets to have similar layers.
A crystallization process
As revealed by NASA’s MESSENGER and Mariner 10 missions, the planet has a large presence of graphite, which gives a dark color to its surface. Until now, scientists thought that graphite was formed by the carbon in its mantle due to pressure and temperature, and that it then floated to the surface because it was lighter than other components.
Everything changes when a 2019 study states that Mercury’s mantle is 80 kilometers (50 miles) deeper than previously thought. This implies that the pressure and temperature are higher, which makes it easier for the carbon to crystallize into diamond. Added to this is the presence of sulphur, which would allow it to solidify at much higher temperatures. Interestingly on other planets, diamond falls in the form of rain.
Yanhao Lin of the Advanced Research Center of High-Pressure Science and Technology in Beijing noticed this. “Many years ago I realized that Mercury’s extremely high carbon content could have significant implications,” he told Phys.org.
Sending a robot to check for the presence of diamond is impossible, so Lin conducted experiments with presses in conditions that simulate the interior of Mercury. By means of 70,000 pascals and 1,970 degrees Celsius, the conditions of the celestial body were emulated with results in accordance with what was proposed. The diamonds would have crystallized in the inner core of the planet, but being less dense than the planet, they emerged to the part adjacent to the core and the mantle.
It is impossible to carry out an extraction at 300 kilometers on Mercury, which already has extreme temperatures of between -180º and 430º. The research could also be a major breakthrough in understanding how planetary layers form. In addition, diamond layers could exist on other planets apart from the one closest to the Sun, which curiously is also the closest to Earth.
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