Unfrozen water content as a function of temperature was measured in the laboratory using pulsed nuclear magnetic resonance (PNMR) for a Windsor sandy loam soil. The PNMR data were related to previously measured soil moisture retention data through the modified Clausius‐Clapeyron equation, with suitable adjustment for surface tension. The transformed measured unfrozen water content data and the previously measured soil moisture retention data were expressed by a Brooks and Corey type of equation with the required set of regression parameters determined. It was found that a single set of parameters were sufficient to correctly express the behavior of these data when suitable constraints were imposed on the unfrozen water content data. Additional insight into the traditional form of expressing unfrozen water content data is presented in terms of air or ice entry pressure.
Cover: This figure demonstrates the strong similarity between the state of air in ice-free soil and ice in air-free colloidfree soil. The two are Indeed Interchangeable through the 0 variable discussed In this report.
One of the scientific objectives of the Viking Mission to Mars was to accomplish an analysis of water in the Martian regolith. The analytical scheme originally envisioned was severely compromised in the latter stages of the Lander instrument package design. Nevertheless, a crude soil water analysis was accomplished. Samples from each of the two widely separated sites yielded roughly 1 to 3% water by weight when heated successively to several temperatures up to 500 degrees C. A significant portion of this water was released in the 200 degrees to 350 degrees C interval indicating the presence of mineral hydrates of relatively low thermal stability, a finding in keeping with the low temperatures generally prevailing on Mars. The presence of a duricrust at one of the Lander sites is taken as possible evidence for the presence of hygroscopic minerals on Mars. The demonstrated presence of atmospheric water vapor and thermodynamic calculations lead to the belief that adsorbed water could provide a relatively favorable environment for endolithic organisms on Mars similar to types recently discovered in the dry antarctic deserts.
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