Ironing out the interiors of exoplanets

Thu, 13 Jan 2022 19:10:55 GMT
Space Daily

Livermore CA (SPX) Jan 14, 2022 The discovery of more than 4,500 extra-solar planets has created a...

Lawrence Livermore National Laboratory scientists and collaborators have used lasers at the National Ignition Facility to experimentally determine the high-pressure melting curve and structural properties of pure iron up to 1,000 GPa, three times the pressure of Earth's inner core and nearly four times greater pressure than any previous experiments.

The team performed a series of experiments that emulate the conditions observed by a parcel of iron descending toward the center of a super-Earth core.

"The sheer wealth of iron within rocky planet interiors makes it necessary to understand the properties and response of iron at the extreme conditions deep within the cores of more massive Earth-like planets," said Rick Kraus, LLNL physicist and lead author of the paper.

"The iron melting curve is critical to understanding the internal structure, thermal evolution, as well as the potential for dynamo-generated magnetospheres."

Earth's magnetodynamo is generated in the convecting liquid iron outer core surrounding the solid iron inner core and is powered by the latent heat released during solidification of the iron.

With the prominence of iron in terrestrial planets, accurate and precise physical properties at extreme pressure and temperatures are required to predict what is happening within their interiors.

A first-order property of iron is the melting point, which is still debated for the conditions of Earth's interior.

It is where a solid turns to a liquid, and the temperature depends on the pressure of the iron.

Through the experiments, the team determined the length of dynamo action during core solidification to the hexagonal close-packed structure within super-Earth exoplanets.

Kraus said: "Beyond our interest in understanding the habitability of exoplanets, the technique we've developed for iron will be applied to more programmatically relevant materials in the future," including the Stockpile Stewardship Program.

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