| Summary: | In a series of laboratory experiments, we measure thermal diffusivity, thermal conductivity, and heat capacity of icy regolith created by vapor deposition of water below its triple point and in a low pressure atmosphere. We find that an ice-regolith mixture prepared in this manner, which may be common on Mars, and potentially also present on the Moon, Mercury, comets and other bodies, has a thermal conductivity that increases approximately linearly with ice content. This trend differs substantially from thermal property models based of preferential formation of ice at grain contacts previously applied to both terrestrial and non-terrestrial subsurface ice. We describe the observed microphysical structure of ice responsible for these thermal properties, which displaces interstitial gases, traps bubbles, exhibits anisotropic growth, and bridges non-neighboring grains. We also consider the applicability of these measurements to subsurface ice on Mars and other solar system bodies. © 2012 by the American Geophysical Union. Received 18 August 2011; revised 20 December 2011; accepted 20 December 2011; published 7 March 2012. We thank Julie Castillo, Doug Cobos, Michael Hecht, Gerard Kluitenberg, Kenneth Libbrecht, Michael Mellon, David Paige, Marsha Presley, Al Slavin, and Steven Wood for their useful discussions and Axel Schmidt for aid in measuring grain surface roughness, Karen Wacker for the construction of and insightful discussion in designing our thermal properties probe, and Hermann Engelhardt, Liz Carey, and Kenny Oslund for years of guidance and dedication in the lab. This work was supported by the Mars Fundamental Research Program. Part of this work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged. Published - Siegler2012p17729J_Geophys_Res-Planet.pdf
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