Water is a scarce commodity on Mars, yet large amounts of water are needed for crew life support, and in most human mission scenarios, even larger amounts of water are needed to produce propellants for departing Mars for the return trip to Earth. There is evidence that significant amounts of water occur as mineral hydration of magnesium sulfates in the accessible upper layer of Mars regolith at various scattered equatorial locations. Several such magnesium sulfates occur on Mars with water content 20% to 50% of the sulfate mass. Several forms of hydrated MgSO4 are known to provide a significant share of observed water-equivalent hydrogen in the upper meter of Mars regolith. These include “Gypsum” (MgSO4⋅2H2O) containing 20.9% H2O by weight, and “Epsomite” (MgSO4·7H2O) (commonly known as “epsom salts”) containing 51% H2O by weight, as well as hexahydrite (MgSO4·6H2O) and starkeyite (MgSO4·4H2O). Scans using the neutron spectrometer from orbit show a remarkable correlation between occurrence of S and H in the equatorial region, indicating that hydrated sulfates are a primary source of H2O there. Recent higher resolution scans using the collimated neutron spectrometer show significant pockets of higher H2O content. This implies that even higher local concentrations of H2O almost surely exist within those areas. The power requirements to evolve H2O from a range of potential hydrated magnesium sulfates are moderate. We suggest that a human mission to Mars at equatorial latitudes based on hydrated sulfates as a source of water is at least as attractive as a mission to higher latitudes based on putative accessible ice.

NASA teams have clarified requirements for a landing site for the first human mission to Mars regarding important factors such as elevation, slope, winds, rock abundance, radar reflectivity, etc. Current planning in the NASA for a landing site for human missions to Mars community is aimed at mission architectures that utilize accessible H2O on Mars to produce several hundred tons of propellants for the return trip using the Starship. This limits the acceptable range of latitude to about 40°N, where observations from orbit suggest that accessible H2O might occur. In this paper, it is shown that a simpler, less demanding architecture for the first human landing on Mars could be carried out without requiring accessible H2O on Mars. With this mission model, the landing site could be chosen at an equatorial site, with several benefits in energy, thermal stability, and solar psychological environment, while avoiding the challenges of locating, verifying H2O, and validating and implementing processes for utilization. Proof of the existence of such accessible H2O requires ground truth, not yet attempted. It is suggested that NASA teams should also consider equatorial landing sites for mission architectures that do not require indigenous Mars H2O, which might be preferred for the first landing. Layman’s explanation With the advent of newly evolving very large, affordable launch vehicles, plans for the first human expedition to Mars have become focused on very ambitious mission concepts that require large amounts of indigenous Mars ice to produce propellants for the return flight from Mars – a significant challenge, complication, and cost and risk additive. This limits potential landing sites to non-equatorial latitudes, which introduces several disadvantages. I propose a smaller, less ambitious mission plan for the first human landing on Mars that doesn’t require Mars ice and therefore could land near the equator. I analyze the water supply for such a mission.

Here, we review the search for H2O that is accessible for utilization by missions to Mars. In that connection, three important parameters that guide us are (1) the latitude, (2) the depth, and (3) the elevation of any H2O. “Accessible” in this review means within about 5 m of the surface, at an elevation at least 2 km lower than the MOLA Datum, and at a latitude within ±20°, possibly extendable to ±30°. This might not be widely shared by members of the community, especially regarding latitude. Twenty years ago, the neutron spectra and initial ice stability models suggested that ground ice on Mars was likely to be rare equatorward of about 50° latitude. Since then, observation after observation from orbit (using radar, photography and spectroscopy) revealed the likely presence of huge amounts of imbedded ice within the subsurface of Mars, at various depths mostly at so-called “mid-latitudes”. As a result, the pendulum has swung to the point that some enthusiastically suggest that ground ice occurs almost everywhere on Mars. We reviewed the various observations and analyses regarding H2O on Mars. Near-surface ice has been observed, spectra and radar have implied, and ground features have been interpreted to indicate that in wide areas of Mars, shallow ice apparently occurs at latitudes greater than 40° and at a few locations, persists into the 30s. The depths of such putative ice are not well known. Further study with much higher resolution might possibly reveal shallow ice at lower latitudes in unique locations. Mineral hydrates might offer a possible alternative as a supply of H2O but not enough is known about local high concentrations because current observation techniques do not penetrate the surface.

SpaceX announced a plan for a bold, innovative, new approach to land a human crew on Mars. Unlike traditional space missions that minimize mass, the SpaceX approach utilizes many lower-cost launches to create a simplified, robust mission concept utilizing large amounts of mass. SpaceX claims it will land a crew on Mars in the next several years. A great deal of development and validation in situ of critical elements of the mission must be demonstrated prior to carrying out the mission. The in situ production of 1,200 MT of cryogenic propellants and the entry descent and landing of a 200 MT vehicle represent the greatest challenges. Locating an accessible source of H2O at a suitable landing site will require a series of launches of prospecting missions at increasing resolution at 26-month launch intervals. The preparation for the ultimate SpaceX mission will require at least ten years and most likely twenty years of development and demonstration at a cost of several tens of billions of dollars. It is not clear why SpaceX continues to make bold claims for timing that is not possible.

The conventional method to send payloads to Mars is by direct trans-Mars injection (TMI) from LEO. NASA is considering an alternative of fueling large Mars-bound cargo transfer vehicles in cis-lunar space with propellants derived from the Moon by in situ propellant production (ISPP) prior to trans-Mars injection from cis-lunar space. A large team of investigators developed an Evolvable Lunar Campaign (ELC) that defined its strategic objective as follows: "The ELC strategic objective is commercial mining of propellant from lunar poles where it will be transported to lunar orbit to be used by NASA to send humans to Mars." Unfortunately, sending Mars-bound vehicles to cis-lunar space prior to trans-Mars injection saves little mass in LEO, unnecessarily includes lunar ISPP, which is costly, complex, and risky, and at the bottom line, has no benefits. The problem is that the amount of propellant needed to go from LEO to cis-lunar space is roughly comparable to the amount of propellant used for direct TMI from LEO, so the lunar-derived propellants only offset a small amount of propellant used to augment Mars Orbit Insertion and Entry, Descent, and Landing, and the amount of propellant required in LEO is almost the same in both cases. The initial mass in low Earth orbit (IMLEO) is not reduced much by utilizing lunar ISPP. At the bottom line, sending Mars-bound MCTV to cis-lunar space adds complexity, cost, and risk and provides essentially no benefits.

The inspirational paper by Ash, Dowler, and Varsi in 1978, proposing to utilize in situ resources on Mars (ISRU) rather than bringing them from Earth, originated the field of Mars ISRU that has been the subject of research ever since. In this paper, we reviewed significant research reported on Mars ISRU since 1978 and reported briefly on accomplishments. We found that prior to 2014, progress on small tasks was sporadic and intermittent, always at low Technology Readiness Level (TRL). In 2014, the National Aeronautics and Space Administration (NASA) took a bold, imaginative, unprecedented step to fund a major project in Mars ISRU: the so-called “MOXIE” (Mars Oxygen In Situ Experiment), in which an oxygen production plant based on solid oxide electrolysis (SOEC) was developed, and finally demonstrated on Mars in 2022 and 2023. While MOXIE leaves behind it a wealth of accomplishments, there remains the need to close remaining gaps with additional laboratory and field work. Solid-oxide electrochemical cell (SOEC) technology has become a major area of worldwide investment for terrestrial energy and CO2 control. There is a very strong overlap between this terrestrial technology and Mars ISRU. NASA has already leveraged the terrestrial development work via MOXIE. NASA can leverage further advances with a comparatively small investment beyond 2023. Because NASA is engaged in a major program to return humans to the Moon, NASA’s focus is on lunar ISRU. Unfortunately, the mission impact and return on investment for lunar ISRU does not compare to that for Mars ISRU. NASA’s concept for Mars ISRU is futuristic, involving autonomous mining, transporting, and processing large amounts of Mars regolith. This might well occur long after initial human landings which could better profit in the near-term from MOXIE technology. By continuing further development of SOEC technology beyond MOXIE, while leveraging large investments in terrestrial applications, NASA can develop the Mars ISRU appropriate to nearer term human missions at modest investment. The goal of this paper is to place the relatively mature MOXIE technology advance and solid oxide electrolysis in general in perspective to the historical evolution of low TRL Mars ISRU technology.

Martian in situ propellant production (ISPP) has a fundamental advantage over lunar ISPP because it has much greater leverage. The value of Martian ISPP per liftoff far exceeds that for the lunar ISPP. This study analyzes the challenges and complexity of lunar ISPP versus Mars ISPP and finds that lunar ISPP is so challenging it might not even be feasible, and if it is feasible, the payoff appears to be limited, while the investment is likely to be great. By contrast, Mars ISPP based on atmosphere only is relatively simple with high payoff. NASA is heavily focused on lunar ISPP and seemingly has diminished interest in solid oxide electrolysis of Martian CO2 to O2 after an extremely successful demonstration on Mars by MOXIE. This might make sense at first glance, but when the 2 leading candidates for lunar ISPP are analyzed in detail, it is found that they are extremely difficult and challenging to implement, the effort and investment involved in developing and implementing them are high, and the potential payoff is limited. By contrast, Mars ISPP by solid oxide electrolysis cell (SOEC) of CO2 is comparatively simple and reliable and has high payoff. A SOEC system is basically landed, and a switch is turned on. The only feedstock is the ubiquitous atmosphere. Lunar ISPP involves a seemingly endless number of complex dynamic steps including autonomous traverses of excavator/haulers to unearth (unmoon?) regolith and deliver it to and from a reactor.

The NASA approach for technology development for missions is to (1) wait for a mission need, and (2) upgrade the technology available at that time, however inadequate. This is illustrated with two important NASA technologies: in situ resource utilization (ISRU) and recycling wastewater. It also serves as a review with 49 references provided. NASA funding for ISRU has been sporadic and minimal, probably because no mission was being implemented that used ISRU. The state of the technology remains underdeveloped. For example, CO2 in the Mars atmosphere supplies carbon and oxygen. However, we still do not have a viable system to acquire CO2 and compress it with acceptable power requirements and adequate lifetime. NASA technology for recycling wastewater was developed for the International Space Station. It requires frequent attention with replenishment and replacement of subsystems. This system appears to be inadequate for Mars missions and there is no evidence that NASA has a viable plan to fix that.

Studies of Mars missions over the past thirty years lacked credible cost estimates, so the total mass of materiel delivered to Low-Earth Orbit (LEO) was typically used as a rough measure of relative mission cost because the complexity of the mission was thought to be roughly proportional to the initial mass in LEO (IMLEO). Historically, high launch costs led to large investments in space hardware development which led to high space mission costs. Reducing mass became the central theme of space mission engineering. We are now entering a new era where launch costs no longer have the impact that they would have two decades ago. Launch costs are coming down to the point where we must ask ourselves whether it now makes sense to bring ascent propellants and life support resources from Earth (with higher reliability as a bonus), as opposed to using in situ propellant production and cycling of life support resources. This paper compares various options for bringing ascent propellants and life support resources from Earth vs. developing in situ. In short, it examines the “take it or make it” options for both technologies. For ISPP, the answer is clear: Mars ISPP is not worth the investment when launch costs are low. For life support, the most robust option is to bring life survival resources from Earth, and only use cycling to upgrade the quality of life for the crew.

The Space Race in the second half of the 20th century was primarily concerned with getting there and back. Gradually, technology and international collaboration opened new horizons, but human activity was mostly restricted around Earth’s orbit, while robotic missions were sent to solar system planets and moons. Now, nations and companies claim extraterrestrial resources and plans are in place to send humans and build bases on the Moon and Mars. Exploration and discovery are likely to be followed by exploitation and settlement. History suggests that the next step is the development of space industry. The new industrial revolution will take place in space. Chemical engineers have been educated for more than a century on designing processes adapted to the Earth’s conditions, involving a range of raw materials, atmospheric pressure, ambient temperature, solar radiation, and 1-g. In space, the raw materials differ, and the unique pressure, temperature and solar radiation conditions require new approaches and methods. In the era of space exploration, a new educational concept for chemical engineers is necessary to prepare them for playing key roles in space. To this end, we introduce Astrochemical Engineering as an advanced postgraduate course and we propose a 2-year 120 ECTS MEng curriculum with a brief description of the modules and learning outcomes. The first year includes topics such as low-gravity process engineering, cryogenics, and recycling systems. The second year includes the utilization of planetary resources and materials for space resources. The course culminates in an individual design project and comprises two specializations: Process Engineering and Space Science. The course will equip engineers and scientists with the necessary knowledge for the development of advanced processes and industrial ecologies based on closed self-sustained systems. These can be applied on Earth to help reinvent sustainability and mitigate the numerous challenges humanity faces.

The authors would like to make the following corrections to the published paper [...]

By the time of the 2022 IAC, NASA's Mars2020 Perseverance rover will have spent 18 months on the surface of Mars, during which time the MOXIE experiment (Mars OXygen ISRU Experiment) will have produced oxygen at night and in the day during both the annual maximum and minimum atmospheric density periods, as well as at many other times during the year. MOXIE is the first demonstration of the use of indigenous resources (ISRU = In Situ Resource Utilization) on the surface of another planet. This paper will present a summary of what MOXIE has accomplished, how its performance on Mars has changed with time, and plans for the future. The paper will also present results from an optimization study of a human-scale MOXIE-type system capable of providing the oxidizer for a 6–person Mars Ascent Vehicle. As an experiment carried inside the rover, MOXIE had to satisfy many constraints that would not apply to an independent, full-scale system. Other potential oxygen-producing technologies should be compared to the optimized human-scale system results summarized in this paper rather than to a simple linear scaling of the mass, power consumption, and oxygen production rate of MOXIE.

This study modeled the performance of a full-scale Mars in situ resource utilization (ISRU) system to produce 30 metric tons of liquid O-2, operated for 14 months at half-hourly intervals as the Mars environment changes diurnally and seasonally. We considered various control options, with particular emphasis on power requirements and required cell voltages. Mars temperature and pressure data at half-hour intervals were obtained from the Mars Perseverance team. The full-scale Mars ISRU system included a mechanical compressor, high-temperature electrolysis of Martian CO2, and a liquefier to produce liquid oxygen. The key factors were (a) maintaining cell voltage well below the Nernst potential for carbon formation from CO and (b) tracking the maximum power, as well as the range of power required, at each half-hourly junction across the 14-month run for each control option. The most favorable control option involved adjusting the compressor revolutions per minute at each half-hour to produce a quasi-steady state of oxygen production in the electrolysis and the liquefaction systems, resulting in the most benign electrolysis settings, the lowest maximum power, and the narrowest range of required power. Other approaches where the compressor was run at a steady state and the oxygen production rate varied with time led to higher electrolysis voltage, higher maximum power, and a wider range of power. This study provides guidance on the optimum operating conditions and power requirements of a Mars ISRU system to produce 30 metric tons of liquid oxygen in 14 months of operation.

This paper proposes a sustainable and equitable policy framework for space exploration and natural resource utilization. The research begins with a detailed review of currently existing national and international policies, laws, and guidelines to identify the gaps and inadequacies of policy and governance for space resource utilization. Analysis of lessons learned from history, politics, and our resource governance regimes for space analogs on Earth provides guidance on best approaches for policy and governance related to space resources. These were be adapted to the special circumstances of space, leading to an improved plan for international management of space resources in an era of increased multinational exploration and ISRU.

The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) is a technology demonstration on the NASA Mars 2020 Perseverance rover. MOXIE is capable of producing 6-10 g/h of oxygen via solid oxide electrolysis of atmospheric carbon dioxide. The Mars 2020 mission has allocated MOXIE a minimum of ten oxygen-producing runs, each with approximately 1 h of oxygen production. Before landing, operations were planned to meet MOXIE's five success criteria. Run structure, constraints, and thorough definition and validation processes were defined. Before producing oxygen for the first time, several checkouts were planned to verify functionality of MOXIE's major subsystems. MOXIE's first oxygen-producing run was planned to produce up to 6 g/h of oxygen for approximately 1 h and measure a conservative range of current and voltage at two inlet mass flow rates. The remaining oxygen-producing runs were planned to measure performance using the largest permissible range of current, voltage and inlet mass flow rate for a wide range of atmospheric densities. Runs were designed to be flexible, allowing modification as operational knowledge accumulates throughout the mission. Validation of runs using models and hardware has demonstrated that MOXIE is ready for surface operations.

MOXIE [Mars Oxygen In Situ Resource Utilization (ISRU) Experiment] is the first demonstration of ISRU on another planet, producing oxygen by solid oxide electrolysis of carbon dioxide in the martian atmosphere. A scaled-up MOXIE would contribute to sustainable human exploration of Mars by producing on-site the tens of tons of oxygen required for a rocket to transport astronauts off the surface of Mars, instead of having to launch hundreds of tons of material from Earth's surface to transport the required oxygen to Mars. MOXIE has produced oxygen seven times between landing in February 2021 and the end of 2021 and will continue to demonstrate oxygen production during night and day throughout all martian seasons. This paper reviews what MOXIE has accomplished and the implications for larger-scale oxygen-producing systems.

MOXIE is a technology demonstration that addresses the Mars 2020 (Perseverance) objective of preparing for future human exploration by demonstrating In Situ Resource Utilization (ISRU) in the form of dissociating atmospheric CO2 into O2. The primary goals of the MOXIE project are to verify and validate the technology of Mars ISRU as a springboard for the future, and to establish achievable performance requirements and design approaches that will lead to a full-scale ISRU system based on MOXIE technology. MOXIE has three top-level requirements: to be capable of producing at least 6 g/hr of oxygen in the context of the Mars 2020 mission (assuming atmospheric intake at 5 Torr, typical of Jezero Crater, and $0~^{\circ}\text{C}$ , typical of the rover interior); to produce oxygen with $>98\%$ purity; and to meet these first two requirements for at least 10 operational cycles after delivery. Since MOXIE is expected to operate in all seasons and at all times of day and night on Mars, these requirements are intended to be satisfied under worst-case environmental conditions, including during a dust storm, if possible.

This book carries out approximate estimates of the costs of implementing ISRU on the Moon and Mars. It is found that no ISRU process on the Moon has much merit. ISRU on Mars can save a great deal of m

HEPA FILTER AND SCROLL PUMP IN SIMULATED MARS CONDITIONS. J. B. McClean, J. P. Merrison, J. J. Iversen, M. B. Madsen, K. Araghi, F. Meyen, W. T. Pike, D. Rapp, G. Sanders, P. Smith, G. Voecks, M. H. Hecht and the MOXIE team. Imperial College London (South Kensington Campus, SW7 2AZ, London, United Kingdom, j.mcclean15@imperial.ac.uk), University of Aarhus, University of Copenhagen, NASA Johnson Space Center, Massachusetts Institute of Technology, Independent contractor, University of Arizona, NASA Jet Propulsion Laboratory.