Low Thermal Conductivity of Carbon Dioxide at High Pressure: Implications for Icy Planetary Interiors

• Published in: Journal of geophysical research. Planets 2022-03, Vol.127 (3), p.n/a
• Main Authors: Shieh, Sean R., Hsieh, Wen‐Pin, Tsao, Yi‐Chih, Crisostomo, Christian, Hsu, Han
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Carbon dioxide measurements; CO2; Diamonds; Domains; Dry ice; Evolution; Heat conductivity; Heat flow; Heat transfer; Heat transmission; High pressure; Mathematical analysis; Planet formation; Planetary evolution; planetary interior; Planetary interiors; Planets; Principles; Room temperature; Solid phases; TDTR; Temperature distribution; Temperature profiles; Terrestrial planets; Thermal conductivity; Thermodynamic properties; Time measurement; Water
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2022JE007180

Carbon dioxide is commonly found in terrestrial planets and its thermal property is relevant to the dynamics and evolution of those terrestrial planets. In this work, we combine time‐domain thermoreflectance measurements and first‐principles calculations to determine the thermal conductivity of CO2 up to 70 GPa at room temperature. Our results show that the thermal conductivity of liquid CO2 is ∼0.22 W m−1 K−1 at 0.3–0.5 GPa and increases to ∼0.28 W m−1 K−1 when the liquid CO2 transforms into molecular solid phase I (dry ice). Upon further compression, the mean value of thermal conductivity of phase I increases to 1.4–2.1 W m−1 K−1 at ∼10 GPa and then slightly drops across the phase I‐III boundary. Phase III exhibits a gentle increase of thermal conductivity with pressure and reaches to a maximum value of ∼4 W m−1 K−1 at ∼45 GPa, but shows an abrupt drop when transforming into a non‐molecular amorphous solid. The pressure evolution of CO2 thermal conductivity across different phases may have significant implications for the heat flow and temperature distribution in the interiors of planets and moons containing CO2. Plain Language Summary Knowledge of thermal conductivity of important planetary materials provides an insightful view and information for understanding the heat flow and temperature profile within planetary bodies. CO2 is an important phase that can be found in Earth and Mars. However, its thermal conductivity under extreme conditions remains largely unknown. In this work, we report the first thermal conductivity measurements of CO2 liquid and solids at pressures up to 70 GPa at room temperature, using time‐domain thermoreflectance coupled with diamond‐anvil cells together with the first‐principles calculations. Our results show that the thermal conductivity of CO2 gradually increases from 0.22 W m−1 K−1 at 0.3–0.5 GPa and reaches a maximum of ∼4 W m−1 K−1 at ∼45 GPa. Importantly, the thermal conductivity of CO2 is much lower than that of H2O. Our results may have critical implications for the temperature profile as well as the formation of liquid water in icy planets. Key Points We present the first thermal conductivity measurements of CO2 to 70 GPa Thermal conductivity of CO2 phase I reaches 1.4–2.1 Wm−1K−1 at ∼10 GPa and CO2 phase III reaches a maximum mean value of ∼4 Wm−1K−1 at ∼45 GPa Thermal conductivity of CO2 is much lower than that of H2O, which may have implications for the formation of liquid water in icy planets