¹Baohua Zhang,^1,2Jianhua Ge,^1,2Zili Xiong,¹Shuangmeng Zhai
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2019JE006194]
¹Key Laboratory for High‐Temperature and High‐Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou, China
²University of Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

How water could affect thermal transport properties is a key question which needs to be quantified experimentally when it is incorporated as structurally bound hydroxyl groups in the lattice of mantle minerals. In this study, thermal diffusivity (D) and thermal conductivity (κ) of San Carlos olivine aggregates with various water contents (up to 0.2 wt.% H₂O) were measured simultaneously using transient plane‐source method up to 873 K and 3 GPa. Experimental results demonstrate water content can significantly reduce the thermal diffusivity (D) and thermal conductivity (κ) of olivine aggregate. With the increase of H₂O content from 0.08 wt.% to 0.2 wt.%, the absolute values of D and κ for olivine samples decrease by 5–13% and 17–33% and by 3–8% and 14–21%, respectively. D and κ of olivine aggregate decrease with temperature but increase with pressure. Heat capacity is influenced by pressure negatively. Combining the present data with surface heat flow of the Moon as well as heat production, the calculated temperature profiles provide new constraints on the lunar geotherm and possible H₂O content in the lunar interior.

^1,2,3N.R. Alsaeed,^4,5B.M. Jakosky
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2019JE006066]
¹Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, CO, USA
²Laboratory for Atmospheric and Space Physics, Boulder, CO, USA
³Mohammed Bin Rashid Space Center, Dubai, UAE
⁴Laboratory for Atmospheric and Space Physics, Boulder, CO, USA
⁵Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA
Published by arrangement with John Wiley & Sons

The current deuterium to hydrogen ratio (D/H) on Mars is enriched by a factor of 5‐6 relative to terrestrial values, suggesting that large amounts of H from water have been lost to space. Loss of H occurs more efficiently than loss of D because H atoms are lighter than D atoms, so the remaining gas becomes enriched in D. We constrain the history of water on Mars using D/H by tracking the supply and loss of H and D in the atmosphere. We examined the evolution of water and D/H from 3.3 Ga to the present, using the measured D/H in an ~3 billion‐year‐old Gale crater mudstone and in the present atmosphere as constraints. We define the boundary conditions by the amount of water present at the surface early in history and the amount of water present today, and incorporate the supply of water from outgassing and loss of H and D to space. The factor‐of‐two enrichment in D/H in the last 3.3 Ga can be produced if loss to space outstrips outgassing. This corresponds to a present‐day 20‐50 m water global equivalent layer (GEL) that is a residual of an initial inventory at 3.3 Ga of 40‐170 m GEL, combined with 5‐100 m GEL outgassed and 20‐220 m GEL lost to space.