Researchers reproduced the conditions seen within super-Earths and giant planet cores using laser-driven compression experiments. The experiment also effectively replicated what occurs during the formation of these objects.
The findings reveal the unusual properties of silica under extreme pressure and smoldering temperatures similar to those present in planetary formation and early evolution, Lawrence Livermore National Laboratory reported.
To make their findings the researchers used laser-driven shock compression and ultrafast diagnostics to measure the melting temperature of silica at five million atmospheres, which can be compared to the pressure of core-mantle boundary pressure for a super-Earth.
"Deep inside planets, extreme density, pressure and temperature strongly modify the properties of the constituent materials," said Lawrence Livermore National Laboratory (LLNL) physicist Marius Millot. "How much heat solids can sustain before melting under pressure is key to determining a planet's internal structure and evolution, and now we can measure it directly in the laboratory."
The new data suggests mantle silicates and core metal have comparable melting temperatures above 300 to 500 GPa, meaning large rocky planets most likely have live oceans of magma deep within.
"In addition, our research suggests that silica is likely solid inside Neptune, Uranus, Saturn and Jupiter cores, which sets new constraints on future improved models for the structure and evolution of these planets," Millot said.
Theses groundbreaking advances were made possible through a new high-pressure growth technique that allowed the team to synthesize millimeter-sized transparent polycrystals and single crystals of stishovite. The crystals allowed the team to conduct the first-ever laser shock compression study of stishovite.
"Stishovite, being much denser than quartz or fused-silica, stays cooler under shock compression, and that allowed us to measure the melting temperature at a much higher pressure," Millot said. "Dynamic compression of planetary-relevant materials is a very exciting field right now. Deep inside planets hydrogen is a metallic fluid, helium rains, fluid silica is a metal and water may be superionic."
The findings were published in a recent edition of the journal Science.
