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Results are reported from a new lunar base study with a concise architectural program: build and operate a human-tended base that produces enough oxygen and hydrogen from lunar polar ice In-Situ Resource Utilization (ISRU) for four flights per year of a reusable lander shuttling between the Lunar Gateway and the base. The study examines for the modern era issues first developed and reconciled by the Robotic Lunar Surface Operations (RLSO) study published in 1990 and resurrected at the 69th IAC in Bremen. The new study updates key assumptions for 1) resources - lunar polar ice instead of ilmenite; 2) solar power - polar lighting conditions instead of the 28-day equatorial lunation cycle; 3) transportation - use of multiple flight systems now in development and planning; 4) base site planning - a range of options near, straddling, and inside permanently shadowed regions; 5) ISRU scenarios - for harvesting ice and for constructing radiation shielding from regolith. As did the original study, RLSO2 combines US experts in mission design, space architecture, robotic surface operations, autonomy, ISRU, operations analysis, and human space mission and lunar surface experience. Unlike the original study, the new study uses contemporary tools: CAD engineering of purpose-design base elements, and integrated performance captured in a numerical operations model. This allows rapid iteration to converge system sizing, and builds a legacy analysis tool that can assess the performance benefits and impacts of any proposed system element in the context of the overall base. The paper presents an overview of the ground rules, assumptions, methodology, operations model, element designs, base site plan, and quantitative findings. These findings include the performance of various regolith and ice resource utilization schemes as a function of base location and lunar surface parameters. The paper closes with short lists of the highest priority experiments and demonstrations needed on the lunar surface to retire key planning unknowns.

NASA’s Resource Prospector (RP) was intended to characterize the three dimensional volatile distribution near, and in, a permanently shadowed region on the moon. During May 2016 several RP hardware components were placed in a cryo-vacuum facility at NASA Glenn Research Center along with lunar simulant soil tubes prepared with varying amounts of water. The objective was simulation of observations during drilling activities on the lunar surface and assessing effective delivery of soil samples for capture and sealing. Here we report the spectral measurements ( ∼ 1600–3400 nm) obtained by one RP instrument while actively drilling. Spectral parameters related to two water ice spectral features near 2000 and 3000 nm were used to monitor the presence of water ice in real-time during drilling. Both parameters provide responses to the drilling activities as soil cuttings are emplaced on the surface and additionally document the sublimation of the ice from the cuttings. Qualitatively, the relative intensities of these parameters as a function of drill depth mimic post-test determinations of the soil water content. These results build confidence that the spectral data can provide information about volatile content in sub-surface materials as it is emplaced onto the surface on a time scale that can be used for real-time decision making regarding delivery of a sample to other analytical devices for more detailed characterization.

Studies of lunar polar volatile deposits are of interest for scientific purposes to understand the nature and evolution of the volatiles, and also for exploration reasons as a possible in situ resource to enable long term human exploration and settlement of the Moon. Both theoretical and observational studies have suggested that significant quantities of volatiles exist in the polar regions, although the lateral and horizontal distribution remains unknown at the km scale and finer resolution. A lunar polar rover mission is required to further characterize the distribution, quantity, and character of lunar polar volatile deposits at these higher spatial resolutions. Here we present a case study for NASA's Resource Prospector (RP) mission concept for a lunar polar rover and utilize this mission architecture and associated constraints to evaluate whether a suitable landing site exists to support an RP flight mission. We evaluate the landing site criteria to characterize the Haworth Crater region in terms of expected hydrogen abundance, surface topography, and prevalence of shadowed regions, as well as solar illumination and direct to Earth communications as a function of time to develop a notional rover traverse plan that addresses both science and engineering requirements. We also present lessons-learned regarding lunar traverse path planning focusing on the critical nature of landing site selection, the influence of illumination patterns on traverse planning, the effects of performing shadowed rover operations, the influence of communications coverage on traverse plan development, and strategic planning to maximize rover lifetime and science at end of mission. Here we present a detailed traverse path scenario for a lunar polar volatiles rover mission and find that the particular site north of Haworth Crater studied here is suitable for further characterization of polar volatile deposits.

The Mojave Volatiles Prospector (MVP) project is a science-driven field program with the goal of producing critical knowledge for conducting robotic exploration of the Moon. Specifically, MVP focuses on studying a lunar mission analog to characterize the form and distribution of lunar volatiles. Although lunar volatiles are known to be present near the poles of the Moon, the three dimensional distribution and physical characteristics of lunar polar volatiles are largely unknown. A landed mission with the ability to traverse the lunar surface is thus required to characterize the spatial distribution of lunar polar volatiles. NASA’s Resource Prospector (RP) mission is a lunar polar rover mission that will operate primarily in sunlit regions near a lunar pole with near-real time operations to characterize the vertical and horizontal distribution of volatiles. The MVP project was conducted as a field campaign relevant to the RP lunar mission to provide science, payload, and operational lessons learned to the development of a real-time, short-duration lunar polar volatiles prospecting mission. To achieve these goals, the MVP project conducted a simulated lunar rover mission to investigate the composition and distribution of surface and subsurface volatiles in a natural environment with an unknown volatile distribution within the Mojave Desert, improving our understanding of how to find, characterize, and access volatiles on the Moon.

We present a mission concept designed at NASA Ames Research Center for a two-probe mission to the dwarf planet Ceres, utilizing a set of small low-cost spacecraft. The primary spacecraft will carry both a mass and an infrared spectrometer to characterize water vapor detected to be emanating from Ceres. Shortly after its arrival a second identical spacecraft will impact Ceres to create an ejecta “plume” timed to enable a rendezvous and sampling by the primary spacecraft. This enables additional subsurface chemistry, volatile content and material characterization, and new science complementary to the Dawn spacecraft, the first to arrive at Ceres. Science requirements, candidate instruments, rendezvous trajectories, spacecraft design and comparison with Dawn science are detailed.

Lunar Crater Observation and Sensing Satellite (LCROSS) impacted the Cabeus crater near the lunar South Pole on 9 October 2009 and generated an impact plume. The hydroxyl (OH) band strength observations obtained from the LCROSS mission are explained with the help of numerical modeling of the impact plume. We provide different models of OH production in the plume and conduct a parametric study to constrain the independent parameters of these models. In particular, detailed lofted grain heating, sublimation and photodissociation models are implemented along with models for H2O and OH production from the residual impact crater. Results show that the likely sources of observed OH are from a small amount of direct/abrasional OH desorption from regolith grains (~28 g) in the crater and from sublimation of water vapor ( O (800 kg)) from lofted regolith-imbued ice grains followed by photodissociation.

Future human exploration of the Moon will likely rely on in situ resource utilization (ISRU) to enable long duration lunar missions. Prior to utilizing ISRU on the Moon, the natural resources (in this case lunar volatiles) must be identified and characterized, and ISRU demonstrated on the lunar surface. To enable future uses of ISRU, NASA and the CSA are developing a lunar rover payload that can (1) locate near subsurface volatiles, (2) excavate and analyze samples of the volatile-bearing regolith, and (3) demonstrate the form, extractability and usefulness of the materials. Such investigations are important both for ISRU purposes and for understanding the scientific nature of these intriguing lunar volatile deposits. Temperature models and orbital data suggest near surface volatile concentrations may exist at briefly lit lunar polar locations outside persistently shadowed regions. A lunar rover could be remotely operated at some of these locations for the ∼ 2–14 days of expected sunlight at relatively low cost. Due to the limited operational time available, both science and rover operations decisions must be made in real time, requiring immediate situational awareness, data analysis, and decision support tools. Given these constraints, such a mission requires a new concept of operations. In this paper we outline the results and lessons learned from an analog field campaign in July 2012 which tested operations for a lunar polar rover concept. A rover was operated in the analog environment of Hawaii by an off-site Flight Control Center, a rover navigation center in Canada, a Science Backroom at NASA Ames Research Center in California, and support teams at NASA Johnson Space Center in Texas and NASA Kennedy Space Center in Florida. We find that this type of mission requires highly efficient, real time, remotely operated rover operations to enable low cost, scientifically relevant exploration of the distribution and nature of lunar polar volatiles. The field demonstration illustrated the need for science operations personnel in constant communications with the flight mission operators and the Science Backroom to provide immediate and continual science support and validation throughout the mission. Specific data analysis tools are also required to enable immediate data monitoring, visualization, and decision making. The field campaign demonstrated that this novel methodology of real-time science operations is possible and applicable to providing important new insights regarding lunar polar volatiles for both science and exploration.

In situ resource utilization (ISRU) may one day enable long duration lunar missions. But the efficacy of such an approach greatly depends on (1) physical and chemical makeup of the resource, and (2) the logistical cost of exploiting the resource. Establishing these key strategic factors requires prospecting: the capability of locating and characterizing potential resources. There is already considerable evidence from orbital and impact missions that the lunar poles harbor plausibly rich reservoirs of volatiles. The next step is to land on the Moon and assess the nature, “ore-grade”, and extractability of water ice and other materials. In support of this next step, a mission simulation was carried out on the island of Hawai’i in July of 2012. A robotic rover, provided by the Canadian Space Agency, carried several NASA ISRU-supporting instruments in a field test to address how such a mission might be carried out. This exercise was meant to test the ability to (a) locate and characterize volatiles, (b) acquire subsurface samples in a volatile-rich location, and (c) analyze the form and composition of the volatiles to determine their utility. This paper describes the successful demonstration of neutron spectroscopy as a prospecting and decision support system to locate and evaluate potential ISRU targets in the field exercise.

The scientific information collected and evaluated using the Near-Infrared Volatile Spectrometer System (NIRVSS) during the 2012 In Situ Resource Utilization (ISRU) field campaign, exhibits variations related to differing surface materials and presence of volatiles during both rover traverses and auger activities demonstrating the promise of using NIRVSS for volatile prospecting on the lunar surface.

The Lunar CRater Observation and Sensing Satellite mission (LCROSS) impacted the moon in a permanently shadowed region of Cabeus crater on October 9th 2009, excavating material rich in water ice and volatiles. The thermal and spatial evolution of LCROSS ejecta is essential to interpretation of regolith properties and sources of released volatiles. The unique conditions of the impact, however, made analysis of the data based on canonical ejecta models impossible. Here we present the results of a series of impact experiments performed at the NASA Ames Vertical Gun Range designed to explore the LCROSS event using both high-speed cameras and LCROSS flight backup instruments. The LCROSS impact created a two-component ejecta plume: the usual inverted lampshade “low-angle” curtain, and a high speed, high-angle component. These separate components excavated to different depths in the regolith. Extrapolations from experiments match the visible data and the light curves in the spectrometers. The hollow geometry of the Centaur led to the formation of the high-angle plume, as was evident in the LCROSS visible and infrared measurements of the ejecta. Subsequent ballistic return of the sunlight-warmed ejecta curtain could scour the surface out to many crater radii, possibly liberating loosely bonded surface volatiles (e.g., H 2 ). Thermal imaging reveals a complex, heterogeneous distribution of heated material after crater formation that is present but unresolved in LCROSS data. This material could potentially serve as an additional source of energy for volatile release.

It is suspected that the lunar exosphere has a dusty component dispersed above the surface by various physical mechanisms. Most of the evidence for this phenomenon comes from observations of “lunar horizon glow” (LHG), which is thought to be produced by the scattering of sunlight by this exospheric dust. The characterization of exospheric dust populations at the Moon is key to furthering our understanding of fundamental surface processes, as well as a necessary requirement for the planning of future robotic and human exploration. We present a model to simulate the scattering of sunlight by complex lunar dust grains (i.e. grains that are non-spherical and can be inhomogeneous in composition) to be used in the interpretation of remote sensing data from current and future lunar missions. We numerically model lunar dust grains with several different morphologies and compositions and compute their individual scattering signatures using the Discrete Dipole Approximation (DDA). These scattering properties are then used in a radiative transfer code to simulate the light scattering due to a dust size distribution, as would likely be observed in the lunar exosphere at high altitudes 10's of km. We demonstrate the usefulness and relevance of our model by examining mode: irregular grains, aggregate of spherical monomers and spherical grains with nano-phase iron inclusions. We subsequently simulate the scattering by two grain size distributions ( 0.1 and 0.3 μ m radius), and show the results normalized per-grain. A similar methodology can also be applied to the analysis of the LHG observations, which are believed to be produced by scattering from larger dust grains within about a meter of the surface. As expected, significant differences in scattering properties are shown between the analyses employing the widely used Mie theory and our more realistic grain geometries. These differences include large variations in intensity as well as a positive polarization of scattered sunlight caused by non-spherical grains. Positive polarization occurs even when the grain size is small compared to the wavelength of incident sunlight, thus confirming that the interpretation of LHG based on Mie theory could lead to large errors in estimating the distribution and abundances of exospheric dust.

The role of water ice clouds in the martian water cycle and climate depends on cloud properties such as particle size and number distribution. These properties, in turn, depend on heterogeneous nucleation parameters which are poorly understood. Here we report laboratory experiments performed under martian temperature and water partial pressure conditions (158–185 K, 9 × 10−7–1 × 10−4 Torr H2O) to determine the critical saturation ratio for ice onset, Scrit, as a function of temperature and dust composition. Using infrared spectroscopy to monitor ice nucleation and growth, we find a significant barrier to ice formation, with a pronounced temperature dependence. Even on clay minerals which show uptake of non-crystalline water before ice nucleation, we find a saturation ratio of 2.5 or more (RHice > 250%) is needed to begin ice growth at temperatures near 160 K. These results could lead to changes of four orders of magnitude in the nucleation rate relative to the presumptions used currently in Mars microphysical models, which commonly set the contact parameter, m, to a single value of 0.95. Our results range from m = 0.84 to m = 0.98. For ice nucleation on Arizona Test Dust, the temperature dependence is described by m = 0.0046 * Tnucl + 0.1085, while m = 0.0055 * Tnucl + 0.0003 on a smectite-rich clay sample. Our findings suggest that cloud formation will be more difficult than previously thought, potentially leading to areas of increased near-surface humidity but generally drier conditions in the atmosphere of Mars, overall.

The Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft will orbit the Moon at an altitude of ≈50 km with a payload that includes the Ultraviolet Spectrometer (UVS) instrument, which will obtain high spectral resolution measurements at near-ultraviolet and visible wavelengths (≈231–826 nm). When LADEE/UVS observes the lunar limb from within the shadow of the Moon it is anticipated that it will detect a lunar horizon glow (LHG) due to sunlight scattered from submicron exospheric dust, as well as emission lines from exospheric gases (particularly sodium), in the presence of the bright coronal and zodiacal light (CZL) background. A modularized code has been developed at NMSU for simulations of scattered light sources as observed by orbiting instruments in lunar shadow. Predictions for the LADEE UVS and star tracker cameras indicate that LHG, sodium (Na) emission lines, and CZL can be distinguished based on spatial morphology and spectral characteristics, with LHG dominant at blue wavelengths (∼250–450 nm) and small tangent heights. If present, LHG should be readily detected by LADEE/UVS and distinguishable from other sources of optical scattering. Observations from UVS and the other instruments aboard LADEE will significantly advance our understanding of how the Moon interacts with the surrounding space environment; these new insights will be applicable to the many other airless bodies in the solar system.

International audience; The mostly carbon dioxide (CO 2) atmosphere of Mars condenses and sublimes in the polar regions, giving rise to the familiar waxing and waning of its polar caps. The signature of this seasonal CO 2 cycle has been detected in surface pressure measurements from the Viking and Pathfinder landers. The amount of CO 2 that condenses during fall and winter is controlled by the net polar energy loss, which is dominated by emitted infrared radiation from the cap itself. However, models of the CO 2 cycle match the surface pressure data only if the emitted radiation is artificially suppressed suggesting that they are missing a heat source. Here we show that the missing heat source is the conducted energy coming from soil that contains water ice very close to the surface. The presence of ice significantly increases the thermal conductivity of the ground such that more of the solar energy absorbed at the surface during summer is conducted downward into the ground where it is stored and released back to the surface during fall and winter thereby retarding the CO 2 condensation rate. The reduction in the condensation rate is very sensitive to the depth of the soil/ice interface, which our models suggest is about 8 cm in the Northern Hemisphere and 11 cm in the Southern Hemisphere. This is consistent with the detection of significant amounts of polar ground ice by the Mars Odyssey Gamma Ray Spectrometer and provides an independent means for assessing how close to the surface the ice must be. Our results also provide an accurate determination of the global annual mean size of the atmosphere and cap CO 2 reservoirs, which are, respectively, 6.1 and 0.9 hPa. They also indicate that general circulation models will need to account for the effect of ground ice in their simulations of the seasonal CO 2 cycle.

The thermal emission spectrometer (TES) and the radio science (RS) experiment flying on board the Mars Global Surveyor (MGS) spacecraft have made observations of atmospheric temperatures below the saturation temperature of carbon dioxide (CO2). This supersaturated air provides a source of convective available potential energy (CAPE), which, when realized may result in vigorous convective mixing. To this point, most Mars atmospheric models have assumed vertical mixing only when the dry adiabatic lapse rate is exceeded. Mixing associated with the formation of CO2 clouds could have a profound effect on the vertical structure of the polar night, altering the distribution of temperature, aerosols, and gasses. Presented in this work are estimates of the total planetary inventory of CAPE and the potential convective energy flux (PCEF) derived from RS and TES temperature profiles. A new Mars Global Circulation Model (MGCM) CO2 cloud model is developed to better understand the distribution of observed CAPE and its potential effect on Martian polar dynamics and heat exchange, as well as effects on the climate as a whole. The new CO2 cloud model takes into account the necessary cloud microphysics that allow for supersaturation to occur and includes a parameterization for CO2 cloud convection. It is found that when CO2 cloud convective mixing is included, model results are in much better agreement with the observations of the total integrated CAPE as well as total column non-condensable gas concentrations presented by Sprague et al. [2005a, GRS measurements of Ar in Mars’ atmosphere, American Astronomical Society, DPS meeting #37, #24.08, and 2005b, Distribution and Abundance of Mars’ Atmospheric Argon, 36th Annual Lunar and Planetary Science Conference, #2085] When the radiative effects of water ice clouds are included the agreement is further improved.

Greenhouse warming due to carbon dioxide atmospheres may be responsible for maintaining the early Earth's surface temperature above freezing and may even have allowed for liquid water on early Mars. However, the high levels of CO2 required for such warming should have also resulted in the formation of CO2 clouds. These clouds, depending on their particle size, could lead to either warming or cooling. The particle size in turn is determined by the nucleation and growth conditions. Here we present laboratory studies of the nucleation and growth of carbon dioxide on water ice under Martian atmospheric conditions. We find that a critical saturation, S = 1.34, is required for nucleation, corresponding to a contact parameter between solid water and solid carbon dioxide of m = 0.95. We also find that after nucleation occurs, growth of CO2 is very rapid and proceeds without a surface kinetic barrier. Because growth would be expected to continue until the CO2 pressure is lowered to its vapor pressure, we expect particles larger than those being currently suggested for the present and past Martian atmospheres. Using this information in a microphysical model described in a companion paper, we find that CO2 clouds are best described as "snow", having a relatively small number of large particles.

Mars Pathfinder made numerous discoveries, one of which was a deep temperature inversion that extended from about 15 km down to 8 km above the surface. It has been suggested by Haberle et al. (1999. J. Geophys. Res. 104, 8957-8974.) that radiative cooling by a water ice cloud may generate such an inversion. Clouds can strongly affect the local air temperature due to their ability to radiate efficiently in the infrared and due to the low air mass of the martian atmosphere, which allows the temperature to change during the relatively short lifetime of a cloud. We utilize a time-dependent microphysical aerosol model coupled to a radiative--convective model to explore the effects water ice clouds have on the local martian temperature profile. We constrain the dust and water vapor abundance using data from the Viking Missions and Mars Pathfinder. Water t ice clouds with visible optical depths of r > 0.1 form readily in these simulations. These clouds alter the local air temperature directly, through infrared cooling, and indirectly, by redistributing atmospheric dust. With this model we are able to reproduce the temperature inversions observed by Mars Pathfinder and Mars Global t Surveyor 2000 Academic Press