Water Ice Deposits Research Articles

Early steps toward the lunar base deployment: Some prospects

The paper deals with key problems related to the initial stage of the Moon exploration in the coming decades. Moon exploration plans are on the agenda of the world's leading powers. Some important issues linked to of the Lunar Base development and the pre-construction studies on the selection of the most suitable regions for the purpose and along with their natural properties are discussed. We consider a scenario in which robots are widely used for further study and exploration of the Moon. The plan includes developing a global geological and geophysical reference network on the lunar surface and use mobile equipment equipped with drilling rigs. Such means (lunar rovers of a new generation) are in demand for the preliminary selection of the most suitable places for the Lunar Base construction as an initial element of the complex lunar infrastructure. Two types of lunar rovers are considered in detail: the prospecting and exploration lunokhod of the middle class “Geologist-Explorer” and the heavy lunokhod “Robot-Geologist”. They are intended to carry out regional geological, geochemical and geophysical surveying, sampling, analysis and comparison of data on the natural conditions of selected areas on promising routes with a radius of up to 500 km on the Near and Far side of the Moon. An important goal is data collection on the availability of such important local resources as water ice, frozen volatile and ore deposits. The issues of safety of humans stay in harsh conditions on the lunar surface and the possibility of protection from external factors are discussed, which plays an important role in the implementation of plans for the future lunar exploration.

Ice caves on Mars: Hoarfrost and microclimates

Caves on planet Mars could potentially contain water ice deposits. Here, the physical processes responsible for the growth and preservation of spelean ice formations on Mars are assessed. Martian caves are situated in environments where phase transitions of water are only by sublimation. The predominant type of cave ice is expected to be perennial hoarfrost that slowly grows in supersaturated cavities. The role of cave microclimates for maintaining ice bodies is evaluated comparatively. Free and forced convection transport less sensible heat than in the denser terrestrial atmosphere. Cooling through sublimation is also expected to be far weaker in Martian caves than in terrestrial caves. Hence, the cooling of ice deposits by flow through the cave, often a crucial factor in terrestrial ice caves, is insignificant on Mars, which limits the geographic extent where cave ice deposits can be expected.

Water ice deposition and growth in molecular clouds

ABSTRACT In interstellar clouds, the deposition of water ice on to grains only occurs at visual extinctions above some threshold value (Ath). At extinctions greater than Ath, there is a (near-linear) correlation between the inferred column density of the water ice and AV. For individual cloud complexes such as Taurus, Serpens, and ρ-Ophiuchi, Ath and the gradients of the correlation are very similar along all lines of sight. We have investigated the origin of this phenomenon, with careful consideration of the various possible mechanisms that may be involved and have applied a full chemical model to analyse the behaviours and sensitivities in quiescent molecular clouds. Our key results are as follows: (i) the ubiquity of the phenomenon points to a common cause, so that the lines-of-sight probe regions with similar, advanced, chemical, and dynamical evolution; (ii) for Taurus and Serpens Ath and the slope of the correlation can be explained as resulting from the balance of freeze-out of oxygen atoms and photodesorption of H2O molecules. No other mechanism can satisfactorily explain the phenomenon; (iii) Ath depends on the local density, suggesting that there is a correlation between local volume density and column density; (iv) the different values of Ath for Taurus and Serpens are probably due to variations in the local mean radiation field strength; (v) most ice is accreted on to grains that are initially very small (<0.01$\,\mu$m); and (vi) the very high value of Ath observed in ρ-Ophiuchi cannot be explained in the same way, unless there is complex microstructure and/or a modification to the extinction characteristics.

Solvent-Free Nanofabrication Based on Ice-Assisted Electron-Beam Lithography.

Advances in electron-beam lithography (EBL) have fostered the prominent development of functional micro/nanodevices. Nonetheless, traditional EBL is predominantly applicable to large-area planar substrates and often suffers from chemical contamination and complex processes for handling resists. This paper reports a streamlined and ecofriendly approach to implement e-beam patterning on arbitrary shaped substrates, exemplified by solvent-free nanofabrication on optical fibers. The procedure starts with the vapor deposition of water ice as an electron resist and ends in the sublimation of the ice followed by a "blow-off" process. Without damage and contamination from chemical solvents, delicate nanostructures and quasi-3D structures are easily created. A refractive index sensor is further demonstrated by decorating plasmonic nanodisk arrays on the end face of a single-mode fiber. Our study provides a fresh perspective in EBL-based processing, and more exciting research exceeding the limits of traditional approaches is expected.

Mapping of Ice Storage Processes on the Moon with Time-dependent Temperatures

Abstract Lunar cold traps are defined by extremely low time-integrated sublimation loss, so that water ice is expected to accumulate in them. Due to the strong dependence of the sublimation rate on temperature, they have heretofore been delineated by the peak rather than the time-averaged sublimation rate. Here, time-averaged sublimation rates are calculated for the south polar region of the Moon based on 11 yr of Diviner surface temperature measurements. Data for each spatial pixel are binned according to subsolar (diurnal) and ecliptic (seasonal) longitude. Frequency-domain filtering of temperature time series is applied to interpolate and smooth the data set. The cold trap area is 17,000 km2 from 80°S to the south pole, about 24% larger than defined by peak temperature. In addition, subsurface ice stability is mapped based on solutions of the heat equation with Diviner surface temperatures as the upper boundary condition. Even a thin layer of dust reduces the sublimation loss dramatically. A third potential mechanism for ice storage, vapor pumping by temperature cycles, is also mapped, based on a model for the time-variable population of adsorbed water molecules on the lunar surface. The area of significant pumping is estimated to be 96,000 km2 poleward of 80°S. In summary, a new processing technique has been developed that exploits information about the time variability of lunar surface temperatures measured by Diviner, and it results in new maps for the geographic distribution of potential water-ice deposits in the south polar region of the Moon.

Characterization of geomorphological features of lunar surface using Chandrayaan-1 Mini-SAR and LRO Mini-RF data

The lunar surface comprises complex geomorphological features, which have been formed by the conjunction of processes namely impact cratering and volcanism. Geological features on the Lunar surface can be bifurcated into two main areas named Maria region and the Highland region. Taurus-Littrow valley, which was the Apollo-17 mission landing site, consisting of unique geomorphological characteristics by having a sample size of both Lunar Maria and Highland regions. The dielectric constant is a parameter that gives an approximate distribution of the constituent material of the target area. It is a complex quantity, which indicates a periodic variation of the electric field. The real part of dielectric constant indicates stored energy and the imaginary part indicates dielectric loss factor or the loss of the electric field in the medium due to continuous varying electric field. Planetary surfaces for which determining dielectric constant is an important analysis for most of the space missions, ground measurement is not feasible. This work includes the machine learning-based modeling of dielectric constant for the Apollo 17 landing site the Taurus-Littrow valley. Based on the surface roughness of the study area, two models Gaussian and Exponential have been implemented and compared for the modeled output of the dielectric constant values.The modeling approaches for dielectric characterization of the lunar surface were implemented on NASA's LRO Mini-RF SAR data and Mini-SAR hybrid-pol data of ISRO's Chandrayaan-1 mission. The coefficient of determination (r2) and the root mean square error (RMSE) of the theoretical Gaussian model was 0.995, 0.042 and the Exponential model was 0.948, 0.1349 respectively. When compared with the already calculated values of dielectric constant from Apollo 17 return samples and literature survey, the Gaussian model gives a better variation. Gaussian model was further applied to the Lunar north pole crater namely Hermite-A crater, whose distinctive geomorphological characteristics and location being lunar north pole region, makes it one of the coldest places in the Solar System and a prominent location of water ice deposits.

Investigating the biological potential of galactic cosmic ray-induced radiation-driven chemical disequilibrium in the Martian subsurface environment

There is growing evidence suggesting the presence of aqueous environment on ancient Mars, raising the question of the possibility of life in such an environment. Subsequently, with the erosion of the Martian atmosphere resulting in drastic changes in its climate, surface water disappeared, shrinking habitable spaces on the planet, with only a limited amount of water remaining near the surface in form of brines and water–ice deposits. Life, if it ever existed, would have had to adapt to harsh modern conditions, which includes low temperatures and surface pressure, and high radiation dose. Presently, there is no evidence of any biological activity on the planet’s surface, however, the subsurface environment, which is yet to be explored, is less harsh, has traces of water in form of water–ice and brines, and undergoes radiation-driven redox chemistry. I hypothesize that Galactic Cosmic Ray (GCR)-induced radiation-driven chemical disequilibrium can be used for metabolic energy by extant life, and host organisms using mechanisms seen in similar chemical and radiation environments on Earth. I propose a GCR-induced radiolytic zone, and discuss the prospects of finding such life with Rosalind Franklin rover of the ExoMars mission.

Obliquity dependence of the formation of the martian polar layered deposits

Mars' polar layered deposits (PLD) are comprised of layers of varying dust-to-water ice volume mixing ratios (VMR) that are thought to record astronomically-forced climatic variation over Mars’ recent orbital history. Retracing the formation history of these layers by quantifying the sensitivity of deposition rates of polar material to astronomical forcing is critical for the interpretation of this record. Using a Mars global climate model (GCM), we investigate the sensitivity of annual polar water ice and dust surface deposition to a variety of obliquity and surface water ice source configurations at zero eccentricity that provide a reasonable characterization of the evolution of the PLD during recent low-eccentricity epochs. The GCM employs a fully interactive dust lifting/transport scheme and accounts for the coupling effects of the physics of dust and water on the transport and deposition of water ice and dust. Under a range of tested obliquities (15°–35°), the predicted net annual accumulation rates range from −1 ​mm/yr to +14 ​mm/yr for water ice and from +0.003 to +0.3 mm/yr for dust. GCM-derived accumulation rates are ingested into an integration model that simulates polar accumulation of water ice and dust over five consecutive obliquity cycles (∼700 thousand years) during a low eccentricity epoch. A subset of integration model simulations predict combined north polar water and dust accumulation rates that correspond to the observationally-inferred average growth rate of the north PLD (0.5 ​mm/yr). These integration model simulation results are characterized by net water transfer from the south to the north polar region. In the north, a ∼230 ​m-thick deposit is accumulated over ∼700 thousand years. Three types of layers are produced per obliquity cycle: a ∼30 m-thick dust-rich (20–30% dust VMR) layer that forms at high, a ∼0.5 m-thick dust lag deposit (pure dust) that forms at low obliquity, and two ∼10 m-thick dust-poor (∼3%) layers that separate the dust rich layers and form when obliquity is increasing or decreasing. The ∼30 m-thick dust-rich layer is reminiscent of a ∼30 m scale length feature derived from analysis of visible imagery of north PLD vertical structure, while the ∼0.5 m-thick dust lag is only a factor of ∼2 smaller than observed “thin layers”. Overall, this investigation provides further evidence for an obliquity forcing in the PLD climate record, and demonstrates the importance of ice-on-dust nucleation in polar depositional processes.

Europa’s surface water ice crystallinity: Discrepancy between observations and thermophysical and particle flux modeling

Physical processing of Europan surface water ice by thermal relaxation, charged particle bombardment, and possible cryovolcanic activity can alter the percentage of the crystalline form of water ice compared to that of the amorphous form of water ice (the “crystallinity”) on Europa’s surface. The timescales over which amorphous water ice is thermally transformed to crystalline water ice at Europan surface temperatures (80–130 K) suggests that the water ice there should be primarily in the crystalline form, however, surface bombardment by charged particles induced by Jupiter’s magnetic field, and vapor deposition of water ice from Europan plumes, can produce amorphous water ice surface deposits on short timescales. The purpose of this investigation is to determine whether the Europan surface water ice crystallinity derived from ground-based spectroscopic measurements is in agreement with the crystallinity expected based upon temperature and radiation modeling. Using a 1D thermophysical model of Europa’s surface, we calculate an integrated full-disk crystallinity of Europa’s leading hemisphere by incorporating the thermal relaxation of amorphous to crystalline water ice and the degradation of crystalline to amorphous water ice by irradiation. Concurrently, we derive the full-disk crystallinity of Europa’s leading hemisphere using a comparison of near-infrared ground-based spectral observations from Grundy et al. (1999), Busarev et al. (2018), and the Apache Point Observatory in Sunspot, NM, with laboratory spectra from Mastrapa et al. (2008) and the Ice Spectroscopy Lab at the Jet Propulsion Laboratory. We calculate a modeled crystallinity significantly higher than crystallinities derived from ground-based observations and laboratory spectra. This discrepancy may be a result of geophysical processes, such as by vapor-deposited plume material, or it may arise from assumptions and uncertainties in the crystallinity calculations.

Lunar Flashlight CubeSat GNC system development

JPL is developing the Lunar Flashlight (LF) CubeSat mission, a 6U 14 kg spacecraft whose objective is to demonstrate new technology and measure potential surface water ice deposits in the permanently shadowed region (PSR) of the moon in preparation of future possible human lunar exploration. This mission will become the first interplanetary CubeSat to orbit the Moon. It uses a new green propulsion system as well as an instrument with spectrally tuned IR laser technology to search for volatiles in a specific region of the moon. The Guidance, Navigation and Control (GNC) system is crucial for delivering the spacecraft from Earth into Lunar orbit and supporting scientific measurements. Due to the challenging lunar orbit insertion and high tip off rate out of launch vehicle's dispenser, the initial design concept using solar sail propulsion accompanied with small commercial-on-the-shelf (COTS) reaction wheels was abandoned mid-course and replaced by a green propulsion system along with larger reaction wheels, both newly developed for LF. However, using thrusters for the small CubeSat created an additional challenge of controlling the spacecraft attitude. The story of the GNC system development, qualifications, technical challenges encountered, and lessons learned are discussed in this paper.

Mars: Life, Subglacial Oceans, Abiogenic Photosynthesis, Seasonal Increases and Replenishment of Atmospheric Oxygen

AbstractThe discovery and subsequent investigations of atmospheric oxygen on Mars are reviewed. Free oxygen is a biomarker produced by photosynthesizing organisms. Oxygen is reactive and on Mars may be destroyed in 10 years and is continually replenished. Diurnal and spring/summer increases in oxygen have been documented, and these variations parallel biologically induced fluctuations on Earth. Data from the Viking biological experiments also support active biology, though these results have been disputed. Although there is no conclusive proof of current or past life on Mars, organic matter has been detected and specimensresemblinggreen algae / cyanobacteria, lichens, stromatolites, and open apertures and fenestrae for the venting of oxygen produced via photosynthesis have been observed. These life-like specimens include thousands of lichen-mushroom-shaped structures with thin stems, attached to rocks, topped by bulbous caps, and oriented skyward similar to photosynthesizing organisms. If these specimens are living, fossilized or abiogenic is unknown. If biological, they may be producing and replenishing atmospheric oxygen. Abiogenic processes might also contribute to oxygenation via sublimation and seasonal melting of subglacial water-ice deposits coupled with UV splitting of water molecules; a process of abiogenic photosynthesis that could have significantly depleted oceans of water and subsurface ice over the last 4.5 billion years.

Seasonal thermal inertia variations at Gale crater: Role of active surface deposition phenomena

Thermal inertia has been found to play a significant role in planetary remote sensing applications, forming the basis of potentially all major lithological discriminations of the planetary surface. It has always been visualised to serve as a distinctive thermal property of the surface with its values remaining fairly constant at least for a short time period, unless the surface undergoes extensive and rapid degradation. Thermal inertia for Mars has been previously calculated from point spectrometer, orbiter and rover measurements and they have been successfully used for surface geologic interpretations. The present study computes surface thermal inertia over 12 sols along Curiosity's traverse at Gale crater using Thermal Infrared Imaging System (THEMIS) and Rover Environmental Monitoring Station (REMS) observations and attempts to analyse the same on a seasonal timescale. We find that surface thermal inertia at Gale follows a seasonal sinusoidal behaviour with the surface exhibiting maximum and minimum thermal inertia values during southern autumn and spring respectively, the difference between them of the order of 300 to 400 t.i.u. We have attempted here to illustrate that the seasonal behaviour seen in surface thermal inertia may be the result of active surface deposition processes localised to Gale. In this regard, we have also explored the potential role of seasonal dust and water ice deposition in contributing to these observed variations, effectively concluding that seasonal dust deposition could be a highly likely cause to which these seasonal thermal inertia changes can be attributed to.

Non-linear flow modelling of a Martian Lobate Debris Apron

AbstractThe Martian mid-latitudes contain numerous small water-ice deposits, collectively termed viscous flow features (VFFs). The shape and topography of the deposits contain information on their past flow history and formation process. In order to access this information, it is imperative to get information on their deformational properties. Here we use a high-resolution digital topography map and ice-penetrating radar data in combination with an inverse method to constrain the deformational properties of a lobate debris apron, a class of VFF, in the southern hemisphere of Mars. We find that while the creep parameter and accumulation rates are not well constrained in absolute values, their ratio is robust. We also find that the creep exponent is most likely n ≤ 3.

Present-day erosion rate of north polar scarps on Mars due to active mass wasting

At the margins of the north polar deposits of dusty water ice on Mars, steep scarps reveal layered deposits that preserve a record of the planet's recent climate changes. Some of these scarps are currently the most active places on Mars with annual avalanches and block falls. We estimated the erosion rate of a steep north polar scarp by automatically identifying newly apparent blocks throughout a time series of HiRISE images. The total depositional volume over three Mars years corresponds to a minimum erosion rate of ~0.3 m3 per Mars year per meter along the scarp, or a minimum average scarp retreat rate of ~0.2 m/kyr. This rate cannot balance published 0.01–1 m/yr viscous flow rates, implying that either lower rates of the latter occur or that other processes contribute more than block falls to the slopes' steepness.

Study of Chang’E-2 Microwave Radiometer Data in the Lunar Polar Region

The Chang’E-2 (CE-2) four-channel microwave radiometer (MRM) data with frequencies of 3 GHz, 7.8 GHz, 19.35 GHz, and 37 GHz have been used to investigate the properties of lunar surface such as regolith thickness, dielectric constant, and titanium abundance within a depth of several meters in middle and low latitudes. The purpose of this work is to take a close look at MRM data in the polar regions of the Moon and analyze the characteristics of the brightness temperature (TB) in permanently shadowed regions (PSRs), especially where evidence of water ice has been found. First, the comparisons of brightness temperature values in the polar region and in low latitudes show that (1) the periodic diurnal (day/night) variation of TB becomes weak in high latitudes since topography plays a dominant role in determining TB in polar region and (2) seasonal effects are more recognizable in polar region than in low latitudes due to the weak illumination condition. Second, even without direct sun illumination, significant seasonal variations of TBs are observed in PSRs, probably caused by the scattering flux from neighboring topography. TB Ratio (TBR) between channel 1 and channel 4, which indicates the differences of TB at different depths of lunar regolith, is higher and shows stronger seasonal variation in PSR than regions with direct illumination. Third, overall the distribution of high TBR values is in consistence with the water ice distributions obtained by the Moon Mineralogy Mapper instrument, the LAMP UV spectra, and the Lunar Prospector Neutron Spectrometer. The proportion of the summation over area with water ice proof in the regions of interest is 0.89 and 0.56 in south pole and north pole, respectively. The causes of the correlation of high TBR between different microwave frequencies and stability of water ice deposits still require further investigation, but MRM data shows unique characteristic in PSRs and could provide important information about the upper few meters of lunar regolith.

The Lunar IceCube EM-1 Mission: Prospecting the Moon for Water Ice

Lunar IceCube is a NASA nanosatellite mission designed to prospect, locate, and measure volumes and composition of water ice deposits and other volatiles on the Moon in support of future exploitation by robots and human explorers. Lunar IceCube is one of several public -private partnerships selected under NASA's Next Space Technologies for Exploration Partnerships Broad Agency Announcement for the development of advanced exploration systems. Among the first small satellites planned to explore deep space, Lunar IceCube, along with the 12 other Exploration Mission One (EM -1) missions will help lay a foundation for future small-scale planetary missions. In addition to providing useful scientific data, Lunar IceCube will help inform NASA's strategy for sending humans farther into the solar system.

Microscopic simulations of laboratory and interstellar ice structure and chemistry

AbstractWe describe recent simulations of interstellar and laboratory ices using the 3-D, off-lattice microscopic Monte Carlo kinetics model MIMICK. The simulations indicate that interstellar ices are capable of achieving porous structures, dependent on physical conditions. In some cases, such structures may be filled as they are formed, by mobile/volatile species such as H2 that become trapped in those structures. Simulations of laboratory water-ice deposition using MIMICK suggest that an additional non-thermal diffusion mechanism is required to reproduce the high degree of porosity achieved for experimental ices at temperatures less than ~80 K. This mechanism is related to the deposition process itself. Simulations of temperature-programmed desorption of mixed molecular ices are ongoing. The interstellar models have also recently been developed to incorporate a full gas-phase chemistry, coupled with the grain-surface chemistry.

About this title - Martian Gullies and their Earth Analogues

Gullies on Mars resemble terrestrial gullies involved in the transport of abundant material down steep slopes by liquid water. However, liquid water should not be stable at the Martian surface. The articles in this volume present the two main opposing theories for Martian gully formation: climate-driven melting of surficial water-ice deposits and seasonal dry-ice sublimation. The evidence presented ranges from remote-sensing observations, to experimental simulations, to comparison with Earth analogues. The opposing hypotheses imply either that Mars has been unusually wet in the last few million years or that it has remained a cold dry desert – both with profound implications for understanding the water budget of Mars and its habitability. The debate questions the limits of remote-sensing data and how we interpret active processes on extra-terrestrial planetary surfaces, even beyond those on Mars, as summarized by the review paper at the beginning of the book.

Unravelling the Mystery of Lunar Anomalous Craters Using Radar and Infrared Observations

In Miniature Radio Frequency (Mini‐RF) radar images, anomalous craters are those having a high circular polarization ratio (CPR) in their interior but not exterior to their rims. Previous studies found that most CPR‐anomalous craters contain permanently shadowed regions and that their population is overabundant in the polar regions. However, there is considerable controversy in the interpretation of these signals: Both water ice deposits and rocks/surface roughness have been proposed as the source of the elevated CPR values. To resolve this controversy, we have systematically analyzed >4,000 impact craters with diameters between 2.5 and 24 km in the Mini‐RF radar image and Diviner rock abundance (RA) map. We first constructed two controlled orthorectified global mosaics using 6,818 tracks of Mini‐RF raw data and then analyzed the correlations between radar CPR and surface slope, RA, and depth/diameter ratios of impact craters. Our results show that CPR‐anomalous craters are distributed relatively uniformly across the lunar surface, with no apparent difference in CPR between the polar, potentially icy, and nonpolar, not icy, craters. Most CPR‐anomalous craters are relatively young with a large depth/diameter ratio, and they actually represent an intermediate stage of crater evolution. Comparison with a two‐component radar scattering model suggests that rocks and surface roughness are major contributors to the observed CPR values. Using craters of 4.7–22 km in diameter with known ages, we find that craters spend up to 120 Ma with a high exterior RA, and ∼3 Ga in the CPR‐anomalous phase.

Glaciation on Mercury: Accumulation and flow of ice in permanently shadowed circum-polar crater interiors

Radar-bright deposits that coincide with regions in permanent shadow typically found within impact craters at and near the poles of Mercury have been interpreted as being composed of water ice. We investigate the dynamic properties of these solid water-ice deposits (glaciers) with the goal of constraining their movement, flow rates, possible deformation, and related structures and deposits. As an end-member, we treat the extreme case of maximum ice accumulation where these deposits fill the crater to the shadow line, an event we would only expect following maximum accumulation conditions such as a large cometary impact or a comet shower. We find that, given the extremely cold conditions and the limited thickness of glaciers, even under the most favorable accumulation conditions, glaciation is cold-based, ice flow velocities are very low (4 × 10−8 m/yr) and, with the exception of a sublimation lag deposit, glaciation is unlikely to leave any significant impact on the terrain. An important accelerator of ice flow is found to be the contribution of lateral heat conduction from the surrounding extremely hot surface terrain (∼225 K average with up to 450 K maximums), which for 55 km craters yields velocities of 10−3 m/yr while for smaller 10 km craters velocities may exceed 1 m/yr, enough to leave a detectable ice deformation imprint such as drop moraines. However given that the observed deposits are substantially below their maximum fill capacities these estimates are unlikely to be attained.