Inside a Diamond Planet: Experimental Investigation of High P-T SiC

Abstract:

The discovery of hundreds of diverse extrasolar planetary systems implies that there are many worlds in the universe unlike our own. Models indicate that carbon-rich planets, composed largely of SiC and C, may be abundant around carbon rich stars (Kuchner and Seager 2005, Moriarty et al 2014). In order to understand the structure and evolution of such an unfamiliar planet, the basic thermodynamic phase relations of the major materials present must first be constrained. Using the laser heated diamond anvil cell (LHDAC) in combination with Raman analysis and X-Ray diffraction, this study investigates the high pressure and temperature phase diagram of SiC. Microprobe and diffraction data indicate that SiC decomposes at high P-T and that the change follows a negative Clapeyron slope. This has interesting implications for the interior “mantle” structure and dynamics of a SiC-based planet.