Although water ice has been detected by satellite observations near the lunar poles, it is unknown if this ice is simply frost on the Moon's surface or if larger ice deposits exist in the subsurface. If ice is present within the subsurface, it is unknown if this ice exists as loose ice grains or as a cement that binds regolith grains together. To create an economically viable extraction and production plan for lunar water ice resources, we must characterize near-surface ice concentration and distribution at small (<10 m) spatial and depth scales. Geophysical methods that can be deployed on the Moon's surface, such as seismic surveying, could supply some of this information for future lunar mine planning. To improve our understanding of how seismic surveying may detect and characterize subsurface lunar ice, we performed laboratory ultrasonic velocity measurements of lunar regolith simulant with variable amounts of granular and cementing ice. These measurements were performed under variable confining pressure (0.005-0.08 MPa) and constant low temperature (-26 degrees C). We used these measurements to calibrate a rock physics model to predict seismic velocity as a function of porosity, pressure, ice concentration and ice texture. Our results show that seismic velocity increases with ice concentration, and this increase is roughly 20 times higher for cementing ice than for granular ice. Our model can be used in future studies to predict how effective seismic methods may be for detecting and characterizing subsurface lunar ice deposits with varying ice properties and geologic complexity.

Many upcoming lunar missions and payloads are targeting the south pole of the Moon, due to the volatiles potentially harboured in this region including ESA's PROSPECT instrument. PROSPECT is designed to sample the lunar regolith within the first meter of the surface and to analyse any volatiles found. Remote sensing methods and a range of datasets including thermal models, illumination models, LRO NAC images, LOLA DEMs and LRO NAC DEMs generated with shape-from-shading, were used to identify suitable areas for PROSPECT science within the south polar region (84-90 degrees S). Sites identified were down selected using a science matrix and scoring sites of interest based on if and how well the point of interest met the science requirements of PROSPECT. The highest scoring sites are presented and proposed to be ideal candidate landing sites for missions targeting the lunar south polar region, especially for missions that are interested in sampling volatiles, micro cold traps and Permanently Shaded Regions (PSRs). Understanding and sampling these colder areas within the south polar region will advance the understanding of volatiles within the lunar surface and volatile transfer.

Due to the lack of in-situ geotechnical data from lunar Permanently Shadowed Regions (PSRs), it is important that a versatile icy regolith simulant be used in terrestrial development of rovers, excavators, and water extractors intended for operating in lunar PSRs. Fine tuning of existing icy regolith simulant properties is not possible; for a given water percentage they either exhibit strength similar to high strength concrete or to sand, but nothing in between. In this work we present a novel method for creating icy lunar regolith simulant, called Pressure Sintered icy lunar regolith Simulant. PSS is notable for being created from solid phase water, and for being tailorable to a wide range of mechanical properties through the sintering of ice and regolith grains, induced by applied uniaxial pressure. Samples were produced at 0%, 2%, 5%, and 10% ice content as measured by weight, and were pressed at four different pressure levels. Penetration resistance was measured for each of these samples, and it was observed that a continuous distribution of penetration resistance levels could be achieved by varying the applied pressure and ice content. Significant relaxation of samples during the pressing process was also observed. The production method for PSS is included, and is followed by the penetration resistance and density results along with some qualitative observations. Finally, we make recommendations for the use of PSS in terrestrial testing activities.

An analytical study into technologies developed for mining water on the Moon has been carried out, and its results demonstrate that methods without the ice phase change are energy efficient. Based on an analysis of temperature distribution over the regolith depth at the lunar poles, it was found that water in the form of ice can be present at depths less than 11 cm. According to their properties, ice regoliths are not loose rocks like dry regoliths but rather hard. With this in mind, a two-phase technology has been proposed to extract water from ice regolith without the ice phase change: the extracted raw material is first crushed and then separated by screening. The regolith hardness rapidly increases as water content increases. Since the equipment mass and power increase as the material hardness increases, in the first phase of the Moon exploration, it is advisable to mine and process ice regoliths with an ice content of similar to 1.6 %, which are relatively soft rocks with a hardness of 2. Small mobile excavators, already developed and tested, can be used for digging such materials, and impact crushers with low weight and power can be used for processing the raw materials. The concept of an integrated system for separating ice from regolith without the ice phase change has been developed based on a selective impact crusher, which combines the operations of crushing the extracted raw materials and separating individual components in one device. Selective impact crushers are the most energy-efficient pieces of equipment for crushing and separating raw materials. The power consumption of the proposed integrated selective crushing system to separate ice from regolith for mining 100 kg of ice per hour is 118 W, which is comparable with the Aqua Factorem system (100 W) and significantly less than the power consumption required for the thermal method, i.e., 800 kW.

Water ice in permanently shadowed regions on the Moon is exposed to galactic cosmic rays (GCRs) and solar energetic particles (SEPs). Because this radiation alters the chemistry of the ice, constraining the total radiation dose is important for understanding both the origin and evolution of the ice. The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard the Lunar Reconnaissance Orbiter (LRO) has measured the energetic charged particle dose rate for more than a solar cycle, providing the longest continuous dataset of radiation in the lunar environment. CRaTER's unique design enables us to measure the dose rates behind three amounts of mass shielding and thus constrain the GCR and SEP dose rates as a function of depth in the regolith. In a further improvement on prior studies, we combine these dose rates with a model for how impact gardening affects the exposure time of the regolith. We can thus calculate the total dose received by water ice in gardened regolith and find that impact-gardened ice has received a dose of similar to 0.1-1 eV molecule-1 over the past 1 Gyr. This dose is one to two orders of magnitude lower than the doses calculated in studies that do not incorporate the effects of gardening. Relatively undisturbed ice may have received a higher dose, but no more than similar to 10 eV molecule-1 in the top centimeter. This result provides a valuable constraint for researchers studying radiation processing of lunar water ice.

The lunar polar regions contain permanently shadowed regions (PSRs) or local topographic depressions that never receive direct sunlight. These environments (< 110 K) have the potential to cold-trap volatile materials in the form of ice, which are essential resources for exploration and industrialization of cislunar space and the Solar System. Orbital observations and those from the LCROSS impactor experiment provide evidence of the existence of water ice and other cold-trapped volatiles in PSRs; however, constraints on volatile abundance and distribution remain ambiguous as individual observations are not always in concord. Here we compile observations indicating the presence of volatiles from ten remotely sensed datasets in 65 PSRs to estimate the locations and mass of water ice deposits. Faustini, Cabeus, de Gerlache, Shoemaker, Haworth, Sverdrup, Slater, and Amundsen are likely the most resource-rich PSRs. Based on co-locations of observations indicative of surface frost and subsurface hydrogen abundance, we find that the craters with the highest potential mass in metric tons (t) of water ice include Cabeus (-11 x 10(6) t), Shoemaker (-5 x 10(6) t), Faustini (-4 x 10(6) t), de Gerlache (-3 x 10(6) t), and Haworth (-3 x 10(6) t). Future prospecting of lunar volatiles and water ice is contingent on filling knowledge gaps in resource potential, notably accurate measurements of grade and depth of volatiles. Our proposed ranking and estimates for resource tonnage are a tool to guide future orbital and landed missions that could accurately determine the resource potential of PSR deposits.

Explosive volcanic eruptions are responsible for producing localized pyroclatic deposits found across the lunar surface. These small localized pyroclastic deposits are thought to have erupted through transient, vulcanian-like eruptions. We used several remote data products, including a water abundance map, to understand the compositional and physical properties of these pyroclastic deposits. Within these deposits, we found strong relationships between water abundance and pyroxene abundance, glass abundance, regolith density scale height, and longitude. These relationships suggest that water abundance can be used to estimate the gas content of an eruption, cooling rate of erupted pyroclasts, optical density of the eruption plume, degree of fragmentation of an eruption, and infer on the distribution of water in the lunar interior. Further, we deduce that the excess water abundance within these pyroclastic deposits represents interior water content, which we tied to other remote measurements that represent important petrological and volcanological parameters to understand eruption dynamics and behavior.

The 2009 Lunar CRater Observation and Sensing Satellite (LCROSS) impact mission detected water ice absorption using spectroscopic observations of the impact-generated debris plume taken by the Shepherding Spacecraft, confirming an existing hypothesis regarding the existence of water ice in permanently shadowed regions within Cabeus crater. Ground-based observations in support of the mission were able to further constrain the mass of the debris plume and the concentration of the water ice ejected during the impact. In this work, we explore additional constraints on the initial conditions of the pre-impact lunar sediment required in order to produce a plume model that is consistent with the ground-based observations. We match the observed debris plume lightcurve using a layer of dirty ice with an ice concentration that increases with depth, a layer of pure regolith, and a layer of material at about 6 m below the lunar surface that would otherwise have been visible in the plume but has a high enough tensile strength to resist excavation. Among a few possible materials, a mixture of regolith and ice with a sufficiently high ice concentration could plausibly produce such a behavior. The vertical albedo profiles used in the best fit model allows us to calculate a pre-impact mass of water ice within Cabeus crater of 5 +/- 3.0 x 10(11) kg and a mass concentration of water in the lunar sediment of 8.2 +/- 0.001 %wt, assuming a water ice albedo of 0.8 and a lunar regolith density of 1.5 g cm(-3), or a mass concentration of water of 4.3 ;+/- 0.01 %wt, assuming a lunar regolith density of 3.0. These models fit to ground-based observations result in derived masses of regolith and water ice within the debris plume that are consistent with in situ measurements, with a model debris plume ice mass of 108 kg.

Water ice has been detected at the lunar poles, but existing and near-future orbital datasets do not have the capabilities to determine its horizontal and vertical distribution at meter to hundred-meter scales relevant for mining operations. Additionally, there has not yet been a coherent geologic model put forward for how ice deposits have formed and evolved that can be used to assist in planning prospecting campaigns or developing relevant hardware. Here, we propose a system model for understanding these deposits at scales of meters to hectares. The model considers sources of water ice, capture at and below the surface, and retention; it focuses heavily on impact gardening as a modifying process that drives changes in how ice is distributed. 3-dimensional stochastic impact simulations are then used to test the system model and explore how ice deposits might evolve over an area the size of a potential mining outpost. The simulation results showed ice concentrations should eventually become fairly homogeneous at meter to hectare scales due to impact gardening, and high concentrations are distributed randomly rather than clustered in Earth-like ore bodies. We found the best ice deposits for extracting likely exist 10s of cm deep or more, even in locations where ice is currently stable at the very surface. Terrestrial mining software was then used to create block models and grade/tonnage curves that can inform future in-situ resource utilization demonstration missions and future mining operations planning.

The heat flux incident upon the surface of an airless planetary body is dominated by solar radiation during the day, and by thermal emission from topography at night. Motivated by the close relationship between this heat flux, the surface temperatures, and the stability of volatiles, we consider the effect of the slope distribution on the temperature distribution and hence prevalence of cold-traps, where volatiles may accumulate over geologic time. We develop a thermophysical model accounting for insolation, reflected and emitted radiation, and subsurface conduction, and use it to examine several idealized representations of rough topography. We show how subsurface conduction alters the temperature distribution of bowl-shaped craters compared to predictions given by past analytic models. We model the dependence of cold-traps on crater geometry and quantify the effect that while deeper depressions cast more persistent shadows, they are often too warm to trap water ice due to the smaller sky fraction and increased reflected and reemitted radiation from the walls. In order to calculate the temperature distribution outside craters, we consider rough random surfaces with a Gaussian slope distribution. Using their derived temperatures and additional volatile stability models, we estimate the potential area fraction of stable water ice on Earth's Moon. For example, surfaces with slope RMS similar to 15 degrees (corresponding to length-scales similar to 10 m on the lunar surface) located near the poles are found to have a similar to 10% exposed cold-trap area fraction. In the subsurface, the diffusion barrier created by the overlaying regolith increases this area fraction to similar to 40%. Additionally, some buried water ice is shown to remain stable even beneath temporarily illuminated slopes, making it more readily accessible to future lunar excavation missions. Finally, due to the exponential dependence of stability of ice on temperature, we are able to constrain the maximum thickness of the unstable layer to a few decimeters. (C) 2017 Elsevier Inc. All rights reserved.