The scientific foundation for this lunar optimism is genuine and hard-won. Soon after the Moon formed roughly 4.5 billion years ago, a prolonged bombardment of asteroids pummeled its surface, carving the pockmarked topography we see today and delivering a cargo of volatile compounds, including water. Near the lunar poles, dozens of crater floors have remained in permanent shadow for about four billion years, never touched by direct sunlight. These cryogenically cold recesses, vividly described as ‘pits of eternal darkness,’ sit at temperatures below about 110 kelvin, or minus 163 degrees Celsius. At such extreme cold they function as ‘cold traps,’ environments in which water ice cannot sublimate away by more than a millimeter in a billion years, even in the hard vacuum at the Moon’s surface. In other words, any ice that arrived with those ancient asteroids has been preserved in a deep freeze longer than complex life has existed on Earth.

Confirmation that this water is actually there came through a succession of Moon-orbiting missions. Since 2013, spacecraft have mapped likely ice deposits at the poles in steadily increasing detail, and some analyses have suggested that as much as a billion tons of water could be sequestered in those shadowed craters. That figure, if accurate, would be transformative. Water is not merely something to drink; it can be split into hydrogen and oxygen to make rocket propellant, breathed as oxygen, used to shield against radiation, and employed in countless industrial processes. The presence of water at the lunar poles changes everything about human visits to the Moon, because it suddenly becomes practical to imagine a ‘Moon village’ where people could survive without importing every last necessity from Earth. Settlers could grow their own food and enjoy showers and functional toilets, luxuries that even astronauts aboard the International Space Station cannot fully take for granted.

It is precisely this possibility that has fueled the boldest pronouncements of the private space sector. Jeff Bezos has spoken of moving heavy industry off Earth and onto the Moon, while Elon Musk has set his sights on ‘self-growing cities’ beyond our planet. These are enticing visions, and the new study does not dismiss them outright. Instead, its author, Dr. Martin Elvis, set out to test them with a deceptively simple feasibility analysis: how much power and water would a large lunar population actually consume, and how long could a settlement of 100,000 or one million people plausibly endure before its most critical resource ran out? The method was a data-driven accounting exercise, comparing known or estimated resource inventories against the demands of human habitation at scale.

The good news, according to the analysis, is that electricity is not the bottleneck. The rims of the craters that contain the pits of eternal darkness are bathed in almost permanent sunlight, which is why they are sometimes, slightly inaccurately, called the ‘peaks of eternal light.’ From these highly illuminated vantage points, it would be possible to generate as much as three gigawatts of electricity using towers a kilometer tall and covered with photovoltaic arrays. To put that in perspective, three gigawatts is on the order of the output of several large conventional power plants, enough to light a sizable industrial economy. Crucially, the study notes that solar panels could plausibly be manufactured on the Moon itself, since there is no shortage of silicon in the lunar crust. Abundant local power could even make AI data centers on the Moon feasible, sited near those sunny peaks, and would represent the beginning of a true lunar economy.

Water is where the arithmetic turns brutal. Even assuming a generous inventory of one billion tons of water to start with, a lunar city without recycling would exhaust its supply in only a few years. The best-case scenario is hardly more comforting: with water recycling at 98 percent efficiency, matching the impressive performance achieved aboard the International Space Station, a one-million-person city would still run out of water in just over a century. That may sound like a long time, but on the timescales of civilization-building it is a blink, and it is fundamentally incompatible with the idea of a permanent, growing settlement. Sustainability, the study concludes, is precisely what large-scale lunar habitation currently lacks.

The problem deepens when the billion-ton figure is scrutinized. Today’s best estimates of the water actually present on the Moon are about thirty times lower than that optimistic ceiling, which shortens the time to water exhaustion by the same factor. Under those more realistic assumptions, even a small city would run dry after roughly a decade of operation. The scale of settlement matters enormously: a modest Moon village of a thousand people, or even a town of ten thousand, could remain sustainable for several centuries or more, because its demands stay within the regenerative capacity of careful recycling and modest extraction. The dream of urban scale, however, collapses under the weight of its own water bill. The difference between a village and a city on the Moon is, quite literally, the difference between centuries of habitability and a single human generation.

Are there ways out of this hydrological dead end? The study outlines several potential solutions, each with its own challenges. Recycling efficiency could be improved by a factor of five or more beyond current spaceflight standards, pushing recovery rates toward theoretical limits. Per-capita water consumption could be lowered through new techniques such as vertical farming, which grows crops in controlled, water-frugal environments. Water could be imported, most plausibly from accessible near-Earth asteroids, some of which are known to carry substantial volatile inventories and are easier to reach than the lunar surface itself in terms of energy requirements. Or, most simply, humanity could find more water on the Moon.

That last hope may be the most promising of all, and it points toward a clear research priority. Current water-surveying techniques, relying on orbital spectrometers and neutron measurements, cannot probe more than a few meters below the lunar surface. Yet the rubble-like layer of broken rock and dust known as the regolith typically extends tens of meters deep, and those unexplored depths within the cold traps may hold substantial additional ice. If the ambitious plans of the space billionaires are ever to be realized, the study argues, finding that deeper water will be the essential first step. Until then, the verdict stands: the Moon has enough water for outposts, villages, and perhaps small towns, but not, on present evidence, for cities. The next great lunar discovery may not be made by a lander or a rover, but by a drill.

For now, the research reframes the conversation around lunar settlement in terms that engineers and policymakers can act upon. Power abundance and water scarcity coexist at the poles, a paradox created by the Moon’s violent history and its airless, frozen geography. Any credible roadmap for human expansion beyond Earth must therefore begin with rigorous resource prospecting, honest accounting of consumption, and technologies that close every possible loop. The pits of eternal darkness have guarded their ice for four billion years; whether they can sustain a civilization is no longer a matter of imagination, but of measurement.

Subject of Research: Sustainability of lunar cities given limited water ice at the Moon's poles

Article Title: No cities on the Moon — there isn’t enough water, scientists say

Article References: No cities on the Moon — there isn’t enough water, scientists say. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Moon, lunar water ice, cold traps, lunar poles, space settlement, water recycling, solar power, regolith, Moon village, Frontiers in Space Technologies, lunar sustainability, space resources

Water is the most valuable resource candidate on the Moon. It can be consumed by astronauts, split into oxygen for breathing, used as radiation shielding, and converted into liquid hydrogen and oxygen propellant, the lifeblood of any space transportation economy. Evidence for lunar water comes from orbital measurements and from NASA’s LCROSS mission, which slammed a kinetic impactor into the permanently shadowed floor of Cabeus crater near the lunar south pole in 2009 and detected water vapour in the ejecta plume. Yet significant uncertainty remains about how much ice exists, where it sits, and whether it appears as thin films, porous frost or consolidated layers, all of which complicate the design of extraction hardware before a single watt of power is budgeted.

The DLR team systematically searched Scopus, Web of Science and Google Scholar for studies that detailed experimental or simulated lunar water extraction with quantitative data. They recorded design, objectives, environmental parameters, masses and power figures for every qualifying study, with at least two reviewers independently verifying each entry. The resulting survey spans an enormous range of scales. Some laboratory experiments processed only a few grams of icy simulant, while the largest test used nearly twenty-nine kilograms. Simulations ranged from millimetre-scale setups to concepts larger than one metre, drawing from a few watts to several solar constants’ worth of concentrated energy.

From this survey, the authors built the first unified classification of extraction methods, grouping designs by their underlying physical mechanism. Thermal extraction dominates the field: heat from solar concentrators, electrical heaters, microwaves or future nuclear sources is applied to icy regolith, causing the ice to sublimate directly into water vapour in the Moon’s near-vacuum. Thermal methods split further by how the soil is handled. In situ approaches heat regolith where it lies, using capture domes, heated rods or corer drills, while excavated approaches truck the soil to a processing unit, either continuously through augers and conveyors or in discrete batches inside crucibles and rotating heated drums.

Beyond heat, three more exotic families appear in the classification. Mechanical extraction, exemplified by the Aqua Factorem concept from the University of Central Florida, treats ice as a mineral ore, grinding icy regolith and separating ice grains pneumatically, magnetically, vibrationally and electrostatically without melting anything. Convection-assisted extraction is represented by the Rocket Mining System developed by Masten, now part of Astrobotic, with Honeybee Robotics and Lunar Outpost, which fires rocket plumes into the soil to fluidise icy regolith and vacuum up the ejected particles. Ionisation extraction, in the form of ablative arc mining, uses an electric arc to ablate and ionise the regolith itself, steering ionised particles into collection reservoirs sorted by mass with electric and magnetic fields, potentially harvesting multiple elements at once.

The review’s most pointed criticism concerns reporting. Ice content was sometimes given as weight percent and sometimes as volume percent. Only twelve of fourteen experimental studies reported electrical power, only nine reported total simulant mass, and a mere five explicitly stated the mass of ice they started with. Simulations fared little better: just six of thirteen listed numerical starting pressures, and only two explicitly mentioned captured water rather than sublimated mass. The median experiment used roughly half a kilogram of simulant, and only one test exceeded five kilograms, leaving the crucial five-to-thirty-kilogram bracket, the bridge to pilot-scale operations, nearly empty. Most experiments ran for minutes to a few hours, and endurance beyond twenty-four hours of steady operation remains essentially untested, leaving questions of hardware degradation unanswered.

To fix this, the authors propose a standardised reporting framework for the field. They call for every study to report total simulant and ice mass, electrical and thermal power with duty cycles, total energy consumed, run times, and captured and recovered water masses, enabling direct calculation of extraction, capture and recovery efficiencies. They also stress that energy accounting must cover the whole chain, not just sublimation. Capturing water vapour, a step handled by cold traps or condensers, introduces additional power draw and losses, so the highest-level metric, total energy per kilogram of recovered water, must include every input. Comparisons, they caution, should only be made between studies at similar environmental fidelity, since a test in a dusty thermal vacuum chamber cannot fairly compete with one run in open laboratory air.

The review also shines a light on a quieter source of inconsistency: the simulants themselves. Icy lunar regolith is prepared in strikingly different ways, from the common gradual freezing or mud-pie method, which produces strong, cemented, permafrost-like material, to vapour deposition and dry-mix sintering, which avoid bulk liquid water and better resemble genuine lunar conditions. Microstructural studies show wet-mixed samples have smaller pores, lower porosity and higher cohesion than sintered ones, directly altering thermal conductivity and vapour transport. Simulant choice matters too: JSC-1, LHS-1, LMS-1, NU-LHT-2M and others differ in particle size distribution and thermal properties, which control permeability and diffusion under low pressure, meaning that two experiments using different simulants may not be comparable at all. And no current simulant fully reproduces real lunar regolith, so terrestrial performance will inevitably deviate from what a lunar mission encounters.

The identified research gaps are as much about integration as invention. Almost no study couples extraction hardware with vapour capture in a single end-to-end test; the few pilot-scale efforts, such as a drilling-based thermal extraction unit that achieved water collection rates up to roughly 0.75 millilitres per minute with recovery efficiencies above eighty percent, and the European LUWEX project validating extraction, capture and purification with up to fifteen kilograms of simulant, remain rare exceptions. Lunar dust, abrasive and electrostatically charged, is barely addressed in extraction designs despite its known threat to mechanisms and thermal surfaces. Pre- and post-processing steps such as prospecting, excavation, beneficiation, purification and storage must be folded into any honest comparison, and scalable surface demonstrations on the Moon itself will ultimately be required to prove that laboratory success survives radiation, vacuum and extreme temperatures.

What emerges from this review is less a ranking of winners and losers than a roadmap for a maturing field. The authors frame their classification as a starting point, to be refined with input from the wider in-situ resource utilisation community, and their standardised metrics as an invitation to collective agreement on terms, definitions and transparent reporting. If researchers adopt them, the next generation of water extraction studies could finally be compared apples to apples, accelerating the selection of architectures capable of turning permanently shadowed craters into the solar system’s first off-world wells. The alternative, the authors imply, is a patchwork of incomparable results that slows the very missions counting on lunar water to fuel humanity’s return to the Moon and, eventually, the journey beyond it.

Subject of Research: Lunar water extraction technologies for in-situ resource utilisation

Article Title: A review of lunar water extraction technologies: comparison, classification, and research gaps

Article References: Kiewiet, L., Fälker, S., & Zabel, P. (2025). A review of lunar water extraction technologies: comparison, classification, and research gaps. Space and Planetary Resources, 1(1), Article 4. https://doi.org/10.1007/s44461-025-00005-4

Image Credits: AI Generated

DOI: 10.1007/s44461-025-00005-4

Keywords: lunar water extraction, in-situ resource utilisation, icy regolith, thermal mining, permanently shadowed regions, LCROSS, water vapour capture, cold traps, lunar regolith simulants, ISRU, Moon, space resources