Researchers have shown through high-energy laser experiments that magnesium oxide is likely the first mineral to solidify in super-Earth formation, crucially impacting these planets’ geophysical evolution.
A new study reveals that magnesium oxide, a key mineral in planet formation, might be the first to solidify in developing “super-Earth” exoplanets, with its behavior under extreme conditions significantly influencing planetary development.
Scientists have for the first time observed how atoms in magnesium oxide morph and melt under ultra-harsh conditions, providing new insights into this key mineral within Earth’s mantle that is known to influence planet formation.
High-energy laser experiments—which subjected tiny crystals of the mineral to the type of heat and pressure found deep inside a rocky planet’s mantle—suggest the compound could be the earliest mineral to solidify out of magma oceans in forming “super-Earth” exoplanets.
“Magnesium oxide could be the most important solid controlling the thermodynamics of young super-Earths,” said June Wicks, an assistant professor of Earth and Planetary Sciences at Johns Hopkins University who led the research. “If it has this very high melting temperature, it would be the first solid to crystallize when a hot, rocky planet starts to cool down and its interior separates into a core and a mantle.”
Implications for Young Planets
The findings are newly published in 
View of laser-driven experiments of shock-compressed magnesium oxide (MgO) within the chamber at the Laboratory for Laser Energetics. High-power laser beams are used to compress MgO samples to pressures beyond those found in the center of Earth. A secondary source of X-rays is used to probe MgO’s crystal structure. Brighter regions are glowing plasma emission over nanosecond timescales. Credit: June Wicks/Johns Hopkins University
Larger than Earth but smaller than giants like DOI: 10.1126/sciadv.adk0306
Other authors are Saransh Singh, Marius Millot, Dayne E. Fratanduono, Federica Coppari, Martin G. Gorman, Jon H. Eggert, and Raymond F. Smith of Lawrence Livermore National Laboratory; Zixuan Ye and Anirudh Hari of Johns Hopkins University; J. Ryan Rygg of the University of Rochester; and Thomas S. Duffy of
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