Duwayne M. Anderson

The interface between ice and silicate surfaces

Abstract Evidence is developed from observations on the behavior of frozen montmorillonite-water systems and other related observations that indicates the existence of an essentially liquid-like, unfrozen, interfacial layer of water separating ice from the silicate surface. The thickness of the interface is shown to vary greatly with temperature; between 0°C. and about −5°C. the thickness ranges from more than 15 A to about 6 A, but below −5°C. down to liquid nitrogen temperatures the thickness varies only from about 6 A to 3 A. At low temperatures it appears that the mobility of the interfacial water is very much diminished and it may assume properties approaching those of a solid. The question of the presence of anomalous phases of ice is examined, and it is concluded that although the possibility must still be allowed, except for the formation of cubic ice by condensation from the vapor at −80°C. or lower, there is at present no proof of the existence of anomalous ice in frozen silicate-water systems. A phase diagram showing the relationships that exist between the interfacial water, water vapor, and ice is presented. In addition to illustrating the vapor pressure and freezing point depressions, it illustrates in a qualitative way the probable increased effect of pressure on the melting point of the ice present over that of a pure water system. Arguments justifying this point are given together with a discussion of the uncertainties in this conclusion.

IONIC MIGRATION AND WEATHERING IN FROZEN ANTARCTIC SOILS

Soils of continental Antarctica are forming in one of the most severe terrestrial environments. Continously low temperatures and the scarcity of water in the liquid state result in the development of desert-type soils. In an earlier experiment to determine the degree to which radioactive NaCl36 would migrate from a shallow point source in permafrost, movement was observed. To confirm this results, a similar experiment involving Na22Cl has been conducted. Significantly less movement of the Na22 ion was observed. Ionic movement in the unfrozen interfacial films at mineral surfaces in frozen ground is held to be important in chemical weathering in Antarctic and other desert soils.

Frost Phenomena on Mars

The hypothesis that the Martian wave of darkening might be a frostheaving phenomenon has been examined. Consideration of the water-vapor sorption characteristics of a silicate mineral surface at temperatures below freezing leads to the conclusion that, without strongly deliquescent salts to attract and retain liquid water in the Martian soil, frost-heaving phenomena are not to be expected on Mars. On the other hand frost-heaving phenomena involving the freezing and thawing of ammonia may be common in the soils of Jupiter.

Mass spectrometric analysis of organic compounds, water and volatile constituents in the atmosphere and surface of Mars: The Viking Mars Lander

Abstract An experiment centering around a mass spectrometer is described, which is aimed at the identification of organic substances present in the top 10 cm of the surface of Mars and an analysis of the atmosphere for major and minor constituents as well as isotopic abundances. In addition, an indication of the abundance of water in the surface and some information concerning the mineralogy can be obtained by monitoring the gases produced upon heating the soil sample. The organic material will simply be expelled by heating to 150°, 300°, and 500° into the carrier gas stream of a gas chromatograph interfaced to the mass spectrometer or by slowly heating the sample in direct communication with the spectrometer. It is planned to analyze a total of up to nine soil samples in order to study diurnal and seasonal variations. The system is designed to give useful data even for minor constituents if the total of organics should be as low as 5ppm. The spectrometer covers the mass range of 12–200 with adequate resolution. The results of these experiments, which are deliberately designed to cover a wide spectrum of possibilities independent of terrestrial models, are expected to produce a good picture of the planets organic chemistry and its possible biological significance as well as allow conclusions regarding the history of the planets atmosphere.

Ice Nucleation and the Substrate-ice Interface

Embryo crystals form by enlargement of one of the normal components of the liquid. This is favoured by reduced molecular motions and a tendency towards more open, hydrogen bonded regions near the interface.

Water vapor adsorption by sodium montmorillonite at −5°C

Abstract A large amount of interest has recently been expressed pertaining to the quantity of physically adsorbed water by the Martian regolith. Thermodynamic calculations based on experimentally determined adsorption and desorption isotherms and extrapolated to subzero temperatures indicate that physical adsorption of more than one or two monomolecular layers is highly unlikely under Martian conditions. Any additional water would find ice to be the state of lowest energy and therefore the most stable form. To test the validity of the thermodynamic calculations we have measured adsorption and desorption isotherms of sodium montmorillonite at −5°C. To a first approximation it was found to be valid.

Alaskan thermokarst terrain and possible martian analog.

A first-order analog to martian fretted terrain has been recognized on enhanced, ERTS-1 (Earth Resources Technology Satellite) imagery of Alaskan Arctic thermokarst terrain. The Alaskan analog displays flat-floored valleys and intervalley uplands characteristic of fretted terrain. The thermokarst terrain has formed in a manner similar to one of the processes postulated for the development of the martian fretted terrain.

Soil and water and its relationship to the origin of life

Soils of the terrestrial planets form at the boundaries between lithosphere, atmosphere and hydrosphere. Biogenesis occurred in these zones; thus, it is axiomatic that some, perhaps many, stages of biogenesis occurred in intimate association with the mineral constituents of soils. Because of a high surface to mass ratio and, consequently, a high surface reactivity, the layer lattice clay minerals are the most important of these. according to the geological record, clay minerals appeared very early on the primordial Earth. Recent investigations have confirmed their presence in carbonaceous meteorites and have indicated their occurrence on Mars.In this paper we collect pertinent physico-chemical data and summarize the organic reactions and interactions that are induced or catalyzed by clays. Many clay-organic reactions that do not occur readily at high water contents proceed rapidly at adsorbed water contents corresponding to surface coverages of one or two molecular layers. One or two monolayers of adsorbed water correspond to extremely dry on cold planetary environments. Some consequences of these factsvis à vis biogenesis on Mars are considered.

BENTONITE DEBRIS FLOWS IN NORTHERN ALASKA

Seasonal freezing and thawing and the extreme cold of the arctic lead to the development of a variety of characteristic geomorphic features. A new one, bentonite debris flow channels, has been identified near Umiat, Alaska. These flows form when bentonite-rich Cretaceous Shales are exposed to Surface water on slopes of 5 to 30 degrees. The characteristic landform developed is a U-shaped channel 1 to 2 meters deep and from 8 to 10 meters in width. The channel shows a fluted floor and walls and is commonly flanked by a levee. The flow material is appa rently derived from the entire surface of the head portions of associated gullies. When this surface layer hydrates during snowmelt and runoff or during prolonged rain, the bentonite imbibes water and swells to a point at which its viscosity is lowered sufficiently to initiate creep or viscous flow.

THE WATER-ICE PHASE COMPOSITION OF CLAY/WATER SYSTEMS. 1. THE KAOLINITE/WATER SYSTEM

Previous studies indicated that when water-ice phase composition curves are normalized to unit surface area, the unfrozen water content values at given temperatures for the kaolinite/water system are higher than those of other soils and soil constitutents. The water-ice phase composition curve for this system has been redetermined using an improved isothermal calorimeter and the earlier curve confirmed. For most soils, water-ice phase composition curves are well represented by a simple power curve. In contrast, the layer-lattice silicate/water systems so far investigated behave differently; segments of two power curves are required to fit the data. Addition of Polyox (polyethylene oxide) to the kaolinite/water system had little effect on the unfrozen water content when the temperture ranged from 0 to 1.7 degrees below freezing but diminished the unfrozen water content significantly at values of 1.7 or more below freezing. Values of the unfrozen water content per kaolinite/water systems are more than twice as large as those for the two representative montmorillonite/water systems investigated. /AUTHOR/