Exoplanets in the Lab
By Aria Elahi, Biology 2017
The shock compression of stishovite and other forms of silica has allowed physicist Mariot Miller of the Lawrence Livermore National Laboratory and his colleagues to replicate theoretical conditions of giant planet cores. This reveals a great deal of the “structure formation and evolution of giant planets and extrasolar terrestrial planets” by discovering the properties of constituents that would exist in these planet cores, such as silica. The aspect that is explored in this experiment is finding the melting points of stishovite at very high pressures, similar to those that would exist in super-Earths.
Using a TW-powered laser pulse, Miller attempted to replicate the high-pressure conditions that would exist on super-Earths such as Neptune and Uranus. This has allowed him to reach significant conclusions about these planets and many other giant planets of the same nature.
“Silica and magnesium oxide are solid in the deep interior of icy giants like Uranus and Neptune, as well as — with extrapolation — in the rocky core of Saturn and Jupiter,” Miller said.
Furthermore, Miller determined that not only do silicates and core metal have melting points above 500 GPa, but that the melting temperature of SiO2 may rise to 8300K at such high pressures.
These findings indicate that large terrestrial planets such as Neptune, Uranus, Saturn, and Jupiter may have long-lived magma oceans that exist within the planets.
This information allows Miller to make fascinating conjectures about the conditions of what these planets may actually be like.
Miller also states that “we find that molten silicate deep within large planetary mantles, in general, can contribute to the magnetic field generation like the iron-rich liquid in the planetary cores. Magnetic fields provide information about the interior dynamics of planets and are potentially observable for exoplanets.”
When silica is shock compressed above 10,000 K it transitions to an electrically conducting state, supporting Miller’s claim of the possibility that these molten liquid silicates may contribute to the magnetic fields inside large planets. This information allows the scientific community to use a greater deal of information when creating models of these dynamic planets.
However, there is still much to learn about the extreme and volatile conditions of these extrasolar planets that Miller and his colleagues plan to explore. The overarching goal of planetary research is not only discovering a great deal about other planets but also revealing the mysterious formation of our own.