This story dives down into the mantles of rocky super-Earths. The work was published in Nature, and it involved lasers. No, seriously, lasers were involved. Big, powerful lasers at the Lawrence Livermore National Laboratory were used to compress iron oxide to pressures between three and five times that of the core-mantle boundary here on Earth. The compression took nanoseconds. Nanoseconds!

A little chemistry now. The iron oxide ended up at twice the density of another common mantle mineral, magnesium oxide, and it underwent a phase transition in the process. Here on Earth, you can easily mix the two minerals together in the mantle, but with that phase transition at high pressures, that’s no longer possible. This means that in a super-Earth, there could be some new physical properties we don’t see here on Earth.

Lead author Federica Coppari explains: Not only are the atoms more tightly packed, this new material phase [of iron oxide] is associated with a dramatic drop in viscosity…[which] plays an important role in the convecting motions inside the mantle. The rheology of a large extrasolar planet might be completely different than that of the Earth…and it’s related to the different material properties at more extreme conditions expected inside exoplanets.

This research shows a new way to experimentally derive some information about the characteristics of a type of planet we don’t have in our own solar system, and this is incredibly impressive to me. I know I joke a lot about planetary formation theories, but I genuinely love all the work being done, and again, this story involved lasers. Woo!

More Information

Eos article

“Implications of the iron oxide phase transition on the interiors of rocky exoplanets,” F. Coppari et al., 2021 February 11, Nature Geoscience