Using math models, scientists have ‘looked’ into the interior of super-Earths and discovered hey may have compounds that are forbidden by the classical rules of chemistry – these substances may increase the heat transfer rate and strengthen the magnetic field on these planets. The researchers attempted to see which compounds may be formed by S, O, and Mg at high pressures. These particular elements were not chosen by chance. “Earth-like planets consist of a thin silicate crust, a silicate-oxide mantle – which makes up ~7/8 of the Earth’s volume and consists more than 90% of silicates and magnesium oxide – and an iron core. We can say that magnesium, oxygen, and silicon form the basis of chemistry on Earth and on Earth-like planets,” says Oganov.Using USPEX algorithm, the researchers investigated various structural compositions of Mg-Si-O that may occur at pressures ranging from 5 to 30 million atmospheres. Such pressures may exist in the interior of super-Earths – planets with a solid surface mass several times greater than the mass of the Earth. There are no planets like this in the solar system, but astronomers know of planets orbiting other stars that are not as heavy as the gas giants, but are considerably heavier than the Earth ie super-Earths. These planets include the recently discovered Gliese 832c, 5X heavier than the Earth, or mega-Earth Kepler-10c, 17X heavier than the Earth.
The results show the interior of these planets may contain the “exotic” compounds MgSi3O12 and MgSiO6. They have many more oxygen atoms than the MgSiO3 on Earth. MgSi3O12 is a metal oxide and a conductor, whereas other substances consisting of Mg-Si-O atoms are dielectrics or semiconductors. Their properties are very different to normal compounds of magnesium, oxygen, and silicon – many of them are metals or semiconductors. This is important for generating magnetic fields on these planets. As magnetic fields produce electrical currents in the interiors of a planet, high conductivity could mean a significantly more powerful magnetic field = more powerful protection from cosmic radiation, and more favourable conditions for life. The researchers also predicted new magnesium and silicon oxides that do not fit in with the rules of classical chemistry – SiO, SiO3, and MgO3, in addition to the oxides MgO2 and Mg3O2 previously predicted by Oganov at lower pressures.
The computer model also enabled the researchers to determine the decomposition reactions that MgSiO3 undergoes at the ultra-high pressures on super-Earths — post-perovskite. “This affects the boundaries of the layers in the mantle and their dynamics. For example, an exothermic phase change speeds up the convection of the mantle and the heat transfer within the planet, and an endothermic phase change slows them down. This means that the speed of motion of lithospheric plates on the planet may be higher,” says Oganov.
Convection, which determines plate tectonics and the mixing of the mantle, can either be faster (speeding up the mixing of the mantle and heat transfer) or slower. In endothermic change, a possible scenario could be the disintegration of a planet into several independently convecting layers, he noted. Earth’s continents are in constant motion, “floating” on the surface of the mantle, which gives volcanism and a breathable atmosphere. If continental drift were to stop, it could have disastrous consequences for the climate. https://mipt.ru/en/news/scientists_say_forbidden_substances_may_increase_heat_transfer_rates_and_strengthen_magnetic_fields_
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