4 Simulating Extraterrestrial Soils: Lunar and Martian Regolith Analogs

• Lunar and Martian regolith are important for research in the context of human space exploration as we develop plans for long-term missions to the Moon and Mars.
• Regolith refers to the loose, fragmented material covering solid planetary surfaces, formed through billions of years of meteorite impacts, solar radiation exposure, and, in the case of Mars, volcanic activity and wind erosion (Mills et al 2022).
• Unlike terrestrial soils, regolith lacks organic matter and contains sharp, abrasive particles, with lunar regolith rich in silicates and nanophase iron, and Martian regolith characterized by basaltic materials and toxic compounds such as perchlorates (Xiong et al 2024, Rzymski et al 2024). Despite these challenges, regolith is considered a key resource for future space missions under the concept of in-situ resource utilization (ISRU).
• Regolith could serve as a construction material for habitats and landing pads, as well as provide radiation shielding, critical in the absence of a protective magnetic field on both the Moon and Mars. Regolith also hold potential for extracting oxygen and water, either bound in mineral forms or as ice, and could be transformed into a growth medium for plants to support human life (Hossain et al 2025, Neukhart 2024, Zhang et al 2023 and Duri et al 2022).
• However, using regolith for biological purposes presents significant challenges due to its extreme pH, low nutrient content, poor water retention, and potential toxicity to plants and microbes. Table 1 compares some physical and chemical characteristics of Lunar and Martian regolith with soil.
• As a result, ongoing research is focused on understanding how to engineer or biologically amend regolith to support microbial activity and plant growth, laying the groundwork for sustainable life-support systems. Studying regolith is, not only essential for understanding planetary geology but also a fundamental step toward enabling human settlement beyond Earth.

Table 1. Lunar and Martian regolith physical characteristics, compared to soil.

Lunar and Martian Regolith and simulants

Understanding the chemical composition (table 2) of Lunar and Martian regolith not only informs us about the geological history and environmental conditions of each planet/moon, but it also plays an important role in planning sustainable long-term missions. On Earth, soil composition affects agriculture, ecosystems, and construction. On the Moon and Mars, the regolith must serve as a construction material, as a source of essential elements like oxygen and water, as a protective layer against radiation, and even a potential growth medium for plants. Understanding these materials at the elemental level is therefore essential to adapt “hostile” extraterrestrial environments into habitable spaces for future explorers.

Table 2. Lunar and Martian regolith elmental composition, compared to soil.

Since actual lunar and Martian regolith is scarce and difficult to obtain, simulants are essential to test technologies and do research on Earth in preparation for future space missions. These materials are used in a wide range of applications, including evaluating construction techniques, developing life support systems, testing in-situ resource utilization (ISRU), and studying plant growth potential in space environments. Different types of simulants have been created to reflect specific regions or characteristics of planetary surfaces: for example, JSC-1A and NU-LHT are designed to simulate lunar mare and highland soils, respectively, while MGS-1 and MMS are formulated to resemble average Martian regolith. While no simulant can perfectly replicate the exact conditions of their extraterrestrial counterparts—such as the presence of nanophase iron or perchlorates—they provide a critical foundation for scientific advancement and mission readiness. Simulants are manufactured by space agencies and companies such as Space Resource Technologies (https://spaceresourcetech.com).

Figure 1. Lunar and Martian regolith simulates (Space Technologies), adapted from Long-Fox and Britt, 2023. A-D Lunar regolith simulants: LHS and LMS are formulated based on the composition of highland (elevated areas, covering ~83% of lunar surface) and mare (low-lying basins, covering ~17% of surface) samples, respectively. E-H Martian regolith simulants: MGS and JEZ are formulated based on the composition of average Martian and Jezero crater regions, respectively.

Microbes survival and adaptation to regolith

The survival of microbes in lunar and Martian regolith is an essential area of research in astrobiology and space biology, particularly to support the provision of element required for long-term space missions, such as the production of oxygen and food. While growth in native, un-modified regolith is unlikely due to the extreme environmental conditions, its amendment with organic matter and water to modify its physical and chemical characteristics could increase the survivability and establishment of different species. Martian regolith, though toxic and dry, contains perchlorates and lacks organic nutrients, yet studies have shown that species such as Bacillus subtilis, Deinococcus radiodurans, and some cyanobacteria can survive—and even grow—when provided with water, light, and CO₂. These microbes use mechanisms like dormancy, spore formation, biofilm production, and protective pigments to withstand harsh conditions including high radiation and desiccation. In contrast, lunar regolith is even more challenging due to its complete lack of volatile organic compounds, nutrients, and extreme temperatures. No viable microbes have been found in lunar samples, and the environment is considered biologically inert. However, in simulated environments, some microorganisms have demonstrated short-term survival. This research has significant implications for planetary protection, as it helps assess the risk of contaminating celestial bodies with Earth life, and for in-situ resource utilization (ISRU), where microbes may one day assist in oxygen production, bioremediation, or regolith conditioning to support plant growth and human habitats.

Taken from Koehle et al 2023

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