Researchers believe that super-Earths’ magnetic fields could shield alien life from harmful radiation.
Researchers studying how magnesium oxide behaves under the extreme conditions deep within planets have unearthed evidence that changes our understanding of planetary evolution, according to the Carnegie Institution. The mantles of Earth and other rocky planets contain a lot of magnesium and oxygen. Researchers say that because of its simplicity, magnesium oxide is a great model for looking at the nature of planetary interiors.
Researchers note that magnesium oxide is particularly resistant to changes when under intense pressures and temperatures. In addition, magnesium oxide has just three unique states with different structures and properties present given specific planetary conditions: Solid under the conditions on the Earth’s surface, liquid at high temperatures, and another structure of the solid at high pressure. Researchers note that the third structure has never been observed in nature or in experiments.
“What was most surprising was how well-behaved magnesium oxide is in the laboratory,” lead author R. Stewart McWilliams, a geophysicist at the Carnegie Institution of Washington, told Space.com. “The physical properties of magnesium oxide look very similar to what has been predicted for decades by theorists. As scientists, we can’t ask for much better.”
“For many decades we have usually imagined terrestrial planets – the Earth, its neighbors such as Mars, and distant super-Earths — as all having Earth-like properties: that is, they have a outer shell or mantle composed of nonmetallic oxides, and an iron rich core which is metallic and from which planetary magnetic fields originate,” Mr. McWilliams added.
“Our results show that the usual assumption that planetary magnetic fields originate exclusively in iron cores is too limiting,” Mr. McWilliams posited. “Magnetic fields might also form within planetary mantles. In fact, this idea has been speculated on for decades, but now we have hard data to show that, indeed, such a ‘mantle-dynamo’ is plausible.”
Mr. McWilliams and his team studied magnesium oxide between pressures of about 3 million times normal atmospheric pressure to million times atmospheric pressure and at temperatures reaching as high as 90,000 degrees Fahrenheit. These conditions, researchers say, are the conditions that exist at the center of our Earth to those of massive exoplanet super-Earths. The found that significant changes in molecular bonding takes place as the magnesium oxide responds to these conditions, including a change to a new high-pressure solid phase.
Researchers also gathered evidence that, when melting, magnesium oxide transforms from an electrically insulating material like quartz to a metal similar to iron.
Mr. McWilliams told Space.com that the super-Earths’ magnetic field could possibly shield alien life from harmful radiation.
“It is often said that life on planets may require the presence of a strong magnetic field to protect organisms from dangerous radiation from space such as cosmic rays — at least this may be true for certain types of life, similar to humans, that live on a planet’s surface,” Mr. McWilliams said. “We find that magnetic fields may occur on a wider range of planets than previously thought, possibly creating unexpected environments for life in the universe.”
The team came to the conclusion that while magnesium oxide is solid and non-conductive under conditions found on present day Earth, the early Earth’s magma ocean might have been able to create a magnetic field. They believe that the liquid phase of magnesium oxide can be found today in the deep mantles of super-Earths. Researchers also theorize that the new high-pressure solid phase can be found on these planets.
“This pioneering study takes advantage of new laser techniques to explore the nature of the materials that comprise the wide array of planets being discovered outside of our Solar System,” said Russell Hemley, director of Carnegie’s Geophysical Laboratory, in a statement. “These methods allow investigations of the behavior of these materials at pressures and temperatures never before explored experimentally.”
The study’s findings were recently published in the journal Science Express.