Iron Carbide at Exoplanetary Core Conditions

The Earth’s core is composed of an iron-rich liquid outer core and a crystalline iron inner core, alloyed with lighter elements, experiencing extreme pressures of up to 360 GPa and temperatures of up to 6500 K. Recently discovered extrasolar planets are believed to have a similar chemical composition, with core pressures reaching up to 1300 GPa and temperatures as high as 10,000 K. Due to its cosmochemical abundance and prevalence in Fe meteorites, carbon is considered a likely light alloying element in the Fe cores of Earth and other rocky exoplanets. However, the lack of data on carbon incorporation into an iron core makes it challenging to model the interior structure and thermal evolution of these planets. To address this challenge, we are investigating the phase stability and equation of state of iron carbides under extreme pressure and temperature conditions through a combination of molecular dynamics simulations and dynamic compression experiments. Our ultimate goal is to provide accurate data to establish improved models of the structure, formation, and evolution of the cores of Earth and carbon-rich exoplanets. This research involves collaborators from Carnegie’s Earth and Planets Laboratory and LLNL and is supported by DOE/NNSA, as well as computational and experimental campaigns at the exascale Frontier supercomputer (INCITE and ALCC awards) and the Omega EP laser facility at LLE (NLUF award).