The mantles of Earth and other rocky planets are rich in magnesium and oxygen. Due to its simplicity, the mineral magnesium oxide is a good model for studying the nature of planetary interiors. New work from a team led by Carnegie's Stewart McWilliams studied how magnesium oxide behaves under the extreme conditions deep within planets and found evidence that alters our understanding of planetary evolution. It is published November 22 by Science Express.
Magnesium oxide is particularly resistant to changes when under intense pressures and temperatures. Theoretical predictions claim that it has just three unique states with different structures and properties present under planetary conditions: solid under ambient conditions (such as on the Earth's surface), liquid at high temperatures, and another structure of the solid at high pressure. The latter structure has never been observed in nature or in experiments.
McWilliams and his team observed magnesium oxide between pressures of about 3 million times normal atmospheric pressure (0.3 terapascals) to 14 million times atmospheric pressure (1.4 terapascals) and at temperatures reaching as high as 90,000 degrees Fahrenheit (50,000 Kelvin), conditions that range from those at the center of our Earth to those of large exo-planet super-Earths. Their observations indicate substantial changes in molecular bonding as the magnesium oxide responds to these various conditions, including a transformation to a new high-pressure solid phase.
In fact, when melting, there are signs that magnesium oxide changes from an electrically insulating material like quartz (meaning that electrons do not flow easily) to a metal similar to iron (meaning that electrons do flow easily through the material).
Drawing from these and other recent observations, the team concluded that while magnesium oxide is solid and non-conductive under conditions found on Earth in the present day, the early Earth's magma ocean might have been able to generate a magnetic field. Likewise, the metallic, liquid phase of magnesium oxide can exist today in the deep mantles of super-Earth planets, as can the newly observed solid phase.
"Our findings blur the line between traditional definitions of mantle and core material and provide a path for understanding how young or hot planets can generate and sustain magnetic fields," McWilliams said.
"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. "These methods allow investigations of the behavior of these materials at pressures and temperatures never before explored experimentally."
Carnegie Institution: http://www.ciw.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
One in five cancers may be caused when common chemicals – deemed safe on their own – blend lethally inside the human body, study reveals
Cosmologist Sean Carroll tackles a deceptively simple question: Why does time exist at all? The potential answers point to a surprising view of the nature of the universe, and our place in it.
We've known we need dark matter since the 1930s, but still haven't found it. The search can't go on forever
Discovery could eventually transform computers as well.
Polymer scientist Christopher Sakezles landed the biggest deal in the reality show’s history
A cleverly designed pipe that uses water's own energy to fight gravity could be used in miniaturised disease labs
A new sensor based on particles whizzing along optical fibres could monitor temperature and radiation in dangerous environments
NASA's InSight mission may be able to use seismic waves from meteorite strikes to probe the Red Planet's interior
Niels Bohr, with his model of the atom, led physics into the quantum era. In the last of this season’s Perimeter Institute public lectures, his grandson Vilhelm will talk about personality and his influences
Simulations of how bird flocks move collectively found that some can be too large for information to pass across the whole group, limiting the size of a flock