Researchers Chart a Course for Sustainable Water Systems in Space

United Kingdom - Ekhbary News Agency

Researchers Chart a Course for Sustainable Water Systems in Space

As humanity's ambitions extend towards establishing permanent outposts on the Moon and Mars, securing a reliable source of clean drinking water emerges as a paramount challenge. The fundamental human requirement for water, coupled with the harsh realities of space – limited resources and prohibitively expensive resupply missions – necessitates the development of robust, self-sustaining systems. Beyond mere survival, water is indispensable for generating breathable oxygen, cultivating edible plants for nutrition, and maintaining basic hygiene, all critical elements for enabling long-duration human presence in extraterrestrial environments.

A significant contribution to this field comes from a recent study published in *Water Resources Research*, which delves into the ongoing efforts and future requirements for sustainable space water systems. The Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS) serves as a testament to the progress made. Currently, the ECLSS demonstrates an impressive capability to reclaim approximately 93% of the water lost by astronauts through urine, sweat, and respiration, drastically reducing the dependency on Earth-based supplies.

However, the study's authors, led by David Bamidele Olawade, a public health researcher affiliated with the University of East London, emphasize that substantial hurdles remain. Future iterations of space water systems must be significantly more energy-efficient, exceptionally durable, and capable of providing a consistent supply of potable water over extended periods without external replenishment. Olawade collaborated on this comprehensive review with James O. Ijiwade, an environmental science and nanotechnology researcher from the University of Ibadan, Nigeria, and Ojima Zechariah Wada, a postdoctoral researcher specializing in water management and environmental biotechnology at Hamad Bin Khalifa University, Qatar.

While the ISS's ECLSS offers a foundational blueprint for closed-loop water reclamation, its limitations become apparent when considering missions beyond low Earth orbit (LEO). The ISS benefits from relatively quick resupply capabilities, but for lunar or Martian bases, the logistical and economic constraints are immense. Official estimates place the cost of delivering just one kilogram of water to orbit in the tens of thousands of dollars, a figure that escalates exponentially for deeper space missions. Furthermore, the limited payload capacity of spacecraft restricts the volume of essential supplies, including water, that can be transported.

Current systems, including the advanced ECLSS, are often too power-intensive for sustained operation beyond LEO and lack the efficiency required for indefinite self-sufficiency. Moreover, the very act of extracting resources in off-world locations presents a unique set of environmental challenges: microgravity, the vacuum of space, extreme temperature fluctuations, stringent weight limitations for equipment, and complex communication and data analysis requirements. In remote regions like the lunar south pole, characterized by long periods of darkness, reliance on solar power becomes problematic, necessitating the development of alternative energy solutions.

Maintenance is another critical consideration. Conventional water recycling systems are susceptible to corrosion and mechanical wear over time. On long-duration missions, where the ability to perform routine repairs is severely limited, the inherent durability and reliability of the systems become paramount. To overcome these obstacles, Olawade and his colleagues examined cutting-edge advancements in filtration technologies, novel disinfection methods, and sophisticated autonomous systems. They concluded that while existing systems provide a valuable starting point, future designs must prioritize energy efficiency and robust construction to withstand the rigors of space and minimize maintenance needs.

A central theme in the review is the critical importance of In-Situ Resource Utilization (ISRU) – the practice of sourcing and utilizing materials found at a destination. This is a cornerstone of NASA's Artemis Program, which aims to establish a lunar base in the resource-rich South Pole-Aitken Basin. China's International Lunar Research Station (ILRS) and the European Space Agency's vision for an "International Moon Village" also prioritize ISRU. The lunar south pole is particularly attractive due to the presence of abundant water ice within permanently shadowed regions (PSRs), offering a potential local water source.

Similar strategic considerations are guiding the planning for Mars exploration. Robotic missions have long identified potential water reserves, particularly in the mid-latitudes. However, the extraction and purification of this extraterrestrial water pose significant technical and logistical challenges. Specialized equipment will be required to access and process water ice trapped within the Martian regolith. Furthermore, the quality of subsurface water on Mars is a concern, with high concentrations of perchlorates and other potentially harmful organic compounds necessitating advanced purification techniques to render it safe for human consumption and life support.

The development of advanced extraction and purification systems is thus intrinsically linked to the need for equally sustainable, durable, and environmentally adapted power sources. In essence, effective space water systems must be closed-loop, highly efficient, and exceptionally robust, all while minimizing power consumption. To meet the substantial energy demands of extraction and purification, the researchers explored various solar and solar-thermal energy applications. These could power essential processes like water pumping, desalination (employing methods such as reverse osmosis or electrodialysis), and purification techniques like photocatalysis and advanced filtration. Such decentralized systems are well-suited for extraterrestrial habitats where large-scale power plants are impractical.

Photothermal systems, which convert solar radiation directly into heat, can be employed for processes like solar distillation and desalination. Hybrid photovoltaic-thermal (PV-T) solutions offer enhanced efficiency by simultaneously generating electricity for pumps and filters while also producing heat for water treatment. However, the inherent limitations of solar power – extended darkness cycles on the Moon's poles and reduced solar intensity on Mars (approximately 43% to 60% of Earth's) – necessitate complementary energy solutions. The study also considers the potential of small modular nuclear reactors, a technology being actively investigated by NASA's Kilopower Reactor Using Stirling Technology (KRUSTY) program for future lunar and Martian bases.

Additionally, the researchers acknowledge recent advancements in bioreactors, which could play a role in waste processing and water recycling, further contributing to a truly closed-loop system.

Ekhbary News Agency