Determining the conditions for thermal stability of global near-surface water ice on the Moon

Absorption and desorption of water vapour in alkyd and polyurethane varnish were studied by quartz crystal microbalance(QCM). The absorption and desorption kinetics curves were Fickian in nature when the relative humidity was higher than 30%, while the solubility followed Henry's law. The average diffusion coefficient D increases linearly with relative humidity. A residual amount of water(about 10% of the equilibrium absorption amount under the condition of RH 100%) was found to remain in the coatings after extended exposure to dry air. FTIR analysis showed that the molecular structure of the coatings changed before absorption and after desorption of water vapour. The results showed that the residual water reacted with the coating molecule and H-bond was formed between water molecule and the C = O group. A considerable part of water in the coatings may transport in a chain mode by replacement. The rate of forming H-bond is much faster than that of diffusion. When the relative humidity is higher than 30%, the concentration of the water in the coatings is sufficient to support the reaction; diffusion is the controlling step of the absorption process, so the kinetics is Fickian. When the RH is lower than 30%, the concentration of the water in the coatings is not sufficient to support the reaction; the reaction rate is lowered to the degree that it is comparable to the rate of diffusion, then the kinetics of the whole process begin to deviate from Fick's law.

Analyses of samples from the Apollo missions suggest that the Moon formed devoid of native water. However, recent observations by Cassini, Deep Impact, Lunar Prospector and Chandrayaan-1 indicate the existence of an active water cycle on the Moon. Here we report observations of this water cycle, specifically detections of near-surface water released into the lunar exosphere by the Neutral Mass Spectrometer on the Lunar Atmosphere and Dust Environment Explorer. The timing of 29 water releases is associated with the Moon encountering known meteoroid streams. The intensities of these releases reflect the convoluted effects of the flux, velocity and impact location of the parent streams. We propose that four additional detected water releases represent the signature of previously undiscovered meteoroid streams. We show that water release from meteoroid impacts is indicative of a lunar surface that has a desiccated soil layer of several centimetres on top of uniformly hydrated soil. We infer that the Moon is currently in the process of losing water that was either delivered long ago or present at its formation.

Lunar Prospector data support the contention that water ice reservoirs exist in the permanently shaded craters near the lunar poles. Yet the question remains whether the detected hydrogen abundance is actually water ice or is hydrogen in some other form. Present plans call for a controlled impact of Lunar Prospector into a polar crater at the end of July, 1999, in an attempt to liberate a small amount of water vapor that may be detected by ground‐ and space‐based observatories. A positive spectral detection of water vapor or its photo‐dissociated byproduct, OH, would be definite proof of the presence of water ice in the regolith. The following represents both an analysis of this method of searching for water ice as well as an announcement to the observing community of the event.

Water vapor sorption and diffusion properties of sulfonated polyimide membranes

Mars’s mid-latitudes, corresponding approximately to the 30°–60° latitude bands in both hemispheres, host abundant water ice in the subsurface. Ice is unstable with respect to sublimation at Mars’s surface beyond the polar regions, but can be preserved in the subsurface at mid-to-high latitudes beneath a centimeters-to-meters-thick covering of lithic material. In Mars’s mid-latitudes, water ice is present as pore ice between grains of the martian soil (termed “regolith”) and as deposits of excess ice exceeding the pore volume of the regolith. Excess ice is present as lenses within the regolith, as extensive layers tens to hundreds of meters thick, and as debris-covered glaciers with evidence of past flow. Subsurface water ice on Mars has been inferred indirectly using numerous techniques including numerical modeling, observations of surface geomorphology, and thermal, spectral, and ground-penetrating radar analyses. Ice exposures have also been imaged directly by orbital and landed missions to Mars. Shallow pore ice can be explained by the diffusion and freezing of atmospheric water vapor into the regolith. The majority of known excess ice deposits in Mars’s mid-latitudes are, however, better explained by deposition from the atmosphere (e.g., via snowfall) under climatic conditions different from the present day. They are thought to have been emplaced within the last few million to 1 billion years, during large-scale mobilization of Mars’s water inventory between the poles, equator, and mid-latitude regions under cyclical climate changes. Thus, water ice deposits in Mars’s mid-latitudes probably host a rich record of geologically recent climate changes on Mars. Mid-latitude ice deposits are leading candidate targets for in situ resource utilization of water ice by future human missions to Mars, which may be able to sample the deposits to access such climate records. In situ water resources will be required for rocket fuel production, surface operations, and life support systems. Thus, it is essential that the nature and distribution of mid-latitude ice deposits on Mars are characterized in detail.

Photonic Crystal Fiber Interferometers (PCFIs) are widely used for sensing applications. This work presents the fabrication and study the characterization of a relative humidity sensor based on a polymer-infiltrated photonic crystal fiber that operates in a Mach- Zehnder Interferometer (MZI) reflection mode. The fabrication of the sensor only involves splicing and cleaving Photonic Crystal Fiber (PCF) with Single Mode Fiber (SMF). A stub of (LMA-10) PCF spliced to SMF (Corning-28). In the splice regions. The PCFI sensor operation based on the adsorption and desorption of water vapour at the silica-air interface within the PCF. The sensor shows a high sensitivity to RH variations from (27% RH - 95% RH), with a change in its reflected power and the position of the interference peaks is found to be shifted that the interference pattern with a 100 nm span can be observed with high humidity sensitivity of (8.49 pm / %RH) is achieved with compact (4mm) PCF length . The sensor has the advantages for suitable for monitoring humidity in microenvironments. The repeatability, long-term stability, measurement accuracy. Wide humidity range. The response time of the sensor is found to be 1.4 sec for a change in RH of 50 %RH. The fast response time suggests that the sensor can potentially be used as a human breath rate monitor in a clinical situation.

A time‐dependent simulation of the argon‐40 exosphere of the Moon shows that the semiannual oscillation of argon detected by the neutral mass spectrometer on the Lunar Atmosphere and Dust Environment Explorer spacecraft is consistent with adsorptive respiration in seasonal cold traps near the lunar poles. The magnitude of the oscillation requires that high‐energy adsorption sites on soil grain surfaces at polar latitudes be as free of water contamination as soils at low latitudes. This requirement is met by the combination of two generally ignored water removal mechanisms: solar wind bombardment of exposed adsorption sites and the serpentinization reaction of water with olivine. The significance of these processes is supported by the lack of evidence of water in Lunar Atmosphere and Dust Environment Explorer data, which, in turn, establishes an upper bound for exospheric transport of water to polar traps at less than 1014 molecules/Ga.

Effects of supercritical CO2 exposure on diffusion and adsorption kinetics of CH4, CO2 and water vapor in various rank coals

Influence of depressed road configuration on downwind pollutant concentrations: A CFD study under various thermal stability conditions

WHO prescribed shelf life assessment of Syzygium cumini extract through chromatographic and biological activity analyses

Increasing effect of biocrusts on evaporation is evidenced by simulating evaporation and diffusion experiments and water stable isotope analysis

Analysis and prediction of water vapor permeation through perfluorosulfonic acid membranes via the solution-diffusion model in a single-membrane dehumidifier module

Tryptophan Oxidation of a Monoclonal Antibody Under Diverse Oxidative Stress Conditions: Distinct Oxidative Pathways Favor Specific Tryptophan Residues.

The dehumidification from a dehumidifier or an air conditioner was employed to achieve a comfortable and desirable indoor environment. Water vapor adsorbed on adsorbent needs to be regenerated when the water vapor exceeds the adsorption capacity. The conventional process for adsorbent regeneration or moisture desorption uses the heat by means of the heater. In the present study, the water vapor desorption from the adsorbent was investigated by using the nonthermal plasma for possible replacement of the electric heater. As a result, the water vapor desorption rate showed superior characteristics in term of energy efficiency, i.e. desorption per unit energy is significantly higher. At the same time, the gradient of water vapor (desorption rate) is significantly higher or quick desorption can be achieved, which leads to more controllable and flexible air conditioning system.

Available potential energy (APE) is defined as the difference between the total static energy of the atmosphere and that of a reference state that minimizes the total static energy after a sequence of reversible adiabatic transformations. Determining the rate at which APE is generated in the atmosphere allows one to estimate the amount of kinetic energy that can be generated by atmosphere flows. Previous expressions for the sources and sinks of APE rely on a dry framework and are limited by the fact that they require prior knowledge of the distribution of latent heat release by atmospheric motion. In contrast, this paper uses a moist APE framework to derive a general formula for the sources and sinks of APE that can be equally applied to dry and moist circulations. Two key problems are addressed here. First, it is shown that any reorganization of the reference state due to diabatic heating or addition of water does not change its total static energy. This property makes it possible to determine the rate of change in APE even in the absence of an analytic formula for the reference state, as is the case in a moist atmosphere. Second, the effects of changing the total water content of an air parcel are also considered in order to evaluate the changes of APE due to precipitation, evaporation, and diffusion of water vapor. Based on these new findings, one can obtain the rate of change of APE from that of atmospheric entropy, water content, and pressure. This result is used to determine the sources and sinks of APE due to different processes such as external energy sources, frictional dissipation, diffusion of sensible heat and water vapor, surface evaporation, precipitation, and reevaporation. These sources and sinks are then discussed in the context of an idealized atmosphere in radiative–convective equilibrium. For a moist atmosphere, the production of APE by the surface energy flux is much larger than any observational or theoretical estimates of frictional dissipation, and, as is argued here, must be balanced by a comparable sink of APE due to the diffusion of water vapor from unstable to stable air parcels.