UC Berkeley professor Burkhard Militzer and former postdoctoral researcher François Soubiran have discovered that super-Earths, exoplanets up to five times the size of Earth, likely have magnetic fields that are generated through their magma oceans.
Their discovery of the magma oceans on super-Earths was published Sept. 24 in the journal Nature Communications and suggested that Earth, in its early years, also had a magma-generated magnetic field. This is in addition to its current magnetic field generated by Earth’s liquid iron core.
“The idea … from the beginning was to try to understand the properties of the interior of super-Earths and how they can have an influence (on) life, especially on this planet,” Soubiran said. “We wanted to see if the magma oceans are conducting… is (this) enough or not?”
One of the key findings of Militzer and Soubiran’s research was the discovery that silicates under intense pressure are electrically conducting, although not as much as copper and iron, Soubiran said. This is significant because at standard temperatures and pressures, silicates are completely insulating, according to a campus press release.
Through performing lengthy calculations, the researchers were able to discover that silicates became modestly conducting when changing from solid to liquid at high pressures and temperatures.
Soubiran and Militzer had access to atomic-scale computer models of minerals that helped them calculate the conductivity of elements and compounds that are common in rocks on Earth, the moon and likely in all of the planets in our solar system. Through plugging in the conductivities into the models of Earth’s interior, they discovered that the rocks containing these compounds are sufficiently conducting to sustain a dynamo effect, and therefore a magnetic field, a campus press release stated.
These findings showed that super-Earths can have a dynamo process, referring to how Earth’s magnetic field is generated and can be “self-amplified” by the convection of liquid, according to Soubiran.
Although the findings were “not very surprising” because of hints that super-Earths were conducting, the findings did show that magma oceans were conducting enough to create magnetic fields, Soubiran said.
The existence of magnetic fields on these exoplanets could be an essential factor for the presence of life, according to Soubiran.
The magnetic fields protect the super-Earths from solar winds that are much stronger than the solar winds on Earth and preserve an atmosphere. Although it is known that magnetic fields protect life on Earth, researchers are unsure if life could exist without a magnetic field, Soubiran said.
“This is why it is important to understand the properties of the super-Earth,” Soubiran said. “The magma ocean could be an indication of a magnetic field. It is not clear that we could have a magnetic field like on Earth.”