b'Tracys SiC high-pressure data can be used to develop these equations.CSiUnder ambient conditions, silicon and carbon atoms are arranged in a diamond-like crystal structure (left image). Above 1 million atmospheres (100 GPa), silicon21carbide (SiC) is transformed to a rock-salt structure, in which the atoms are squeezed much closer together (right). Image courtesy Sally June Tracy, Carnegie Institution for ScienceLow-pressure 3C phase High-pressure rock-salt phaseInterior mantles of carbon-rich super-Earths, exoplanets up to about 10 Earth-masses, areLaser compression +expected to contain different forms of SiC.pump-probe X-ray diffractionHowever, models disagree about how the material behaves under extreme pressures. At about 1 million atmospheres (100 GPa), when SiC begins to transform to the rock-salt structure there is a ~20%sampledensity jump, which would affect interior structure,cassettedynamics, and heat-loss rate. But reliable equations on the relationship of pressure, temperature, anddetector x-rayvolume at those high pressures are lacking so accurate modeling has been hampered.lasersTracys SiC high-pressure data can be used toThis diagram shows how the rapid, pulsed-pressure develop these equations. Driscoll will then be abletechnique called dynamic compression works. Samples are to develop mathematical models of super-Earthsmounted on a translatable cassette. High-powered lasers launch a shock wave into the sample while high-intensity internal structures to understand how they developX-rays take a series of snap shots read by a detector as and evolve. Tracy and Driscoll will also explore otherthe shock alters the materials atomic configuration. carbon-bearing materials and apply this data to otherImage courtesy Gregory Stewart, SLAC models to constrain the structure and evolution of planetary interiors. The artwork at left shows an exoplanet with a graphite Carbon Planet Silicate Earth surface surrounding an internal diamond layer, then a silicon carbide (SiC) layer around an iron core. The silicates diagrams at right show how SiC from the ambient cubic 3C-SiC carbon (3C) phase changes to the high-pressure rock-salt form in a carbon exoplanet. The diagram on the RS-SiC right shows silicates in the deep Earth. Details of how Iron alloy core transformations occur as a function of temperature-pressure are believed to have profound influence on the interior structure and dynamics of a carbon world. Left image courtesy Haven Giguere, used with the permission of Yale University; right imagecourtesy Sally June Tracy, Carnegie Institution for Science'