The Potential for Lunar and Martian Regolith Simulants to Sustain Plant Growth: A Multidisciplinary Overview

In the paper

“although there is some evidence of a biofilm (Thomas-Keprta et al., 2014;Eigenbrode et al., 2018).”

What the sources say

• ?Not checked — no full text of the sourcecites Thomas-Keprta et al., 2014 source
• Disputed

  The main text (p. 9) says the detected organic matter has no clearly identified source: biological, geological, and meteoritic origins are all possible. It does not present the material as evidence of a biofilm, and it reports no findings about lunar soil. (LLM, conf=0.78)

  Checked by a reasoning model — may be wrong.

  cites Eigenbrode et al., 2018 sourceExperimental — accuracy not yet measured

In the paper

“Space farming based on local resource exploitation (Maggi and Pallud, 2010;Ramírez et al., 2019) is a promising strategy for food production (Ming and Henninger, 1989) on extra-terrestrial habitats, as it can allow water recycling, organic waste composting, and oxygen production or CO 2 consumption (Verseux et al., 2016;Llorente et al., 2018).”

What the sources say

• ?Not checked — no full text of the sourcecites Maggi and Pallud, 2010 source
• Supported

  The Introduction supports the part attributed to Ramírez et al. (2019): it describes soil-based agriculture using in-situ Martian resources as important for the long-term sustainability of a future Mars colony. The sentence cites other works for food production and for water, waste, and gas-cycle benefits; those are not attributed to this source. (LLM, conf=0.91)

  cites Ramírez et al., 2019 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Ming and Henninger, 1989

In the paper

“Studies report that the Martian and Lunar simulants have a pH above 6, and have alkaline properties in some cases (Gilrain et al., 1999;Zaets et al., 2011;Wamelink et al., 2014;Caporale et al., 2020;Eichler et al., 2021), suggesting low rates of mineral weathering and cation release.”

What the sources say

• ?Not checked — no full text of the sourcecites Gilrain et al., 1999 source
• ?Not checked — no full text of the sourcecites Zaets et al., 2011 source
• Supported

  Table 2 (Materials and Methods > Regoliths; page unavailable) reports pH 7.3 for the Mars simulant and 9.6 for the lunar simulant. Both exceed 6, and the lunar simulant is alkaline. The weathering and cation-release statement follows the citations as the citing authors’ inference, rather than a finding attributed to this source. (LLM, conf=0.92)

  cites Wamelink et al., 2014 source

In the paper

“Most existing simulants were developed to address specific application fields, and although their chemical interactions or properties related to mechanical abrasion have been assessed to mitigate potential risks (Rickman et al., 2013), their agricultural properties have rarely been evaluated.”

What the sources say

• Partly supported

  The Abstract says simulants are tested to mitigate risks to lunar-surface equipment and compared by physical properties and bulk chemistry. It does not establish that most simulants were developed for specific applications or that chemical interactions and abrasion properties have been assessed. The statement about rarely evaluated agricultural properties follows the citation and is not clearly attributed to Rickman et al. (LLM, conf=0.72)

  cites Rickman et al., 2013 sourceExperimental — accuracy not yet measured

In the paper

“Three species flowered, but only two produced seeds.”

What the sources say

• Supported

  The Conclusions state that rye, cress and field mustard flowered, and that the latter two also formed seeds. The Results likewise identify those three species as reaching the flower-or-seed stages and name field mustard and cress as the seed producers. (LLM, conf=0.95)

  cites Wamelink et al., 2014 source

In the paper

“The biomass production was highest in the Earth control and the Martian soil simulant, but was significantly lower in the Lunar simulant.”

What the sources say

• Partly supported

  Section 3.1 (Fruit setting and biomass) reports that total aboveground biomass was highest in the Earth control and lowest in the Moon simulant, with Moon dry biomass significantly below Earth (p=0.0318). It also states that Mars biomass was not significantly different from either Earth or Moon, so the claim is unsupported if it implies a significant Mars–Moon difference. (LLM, conf=0.90)

  cites Wamelink et al., 2019 sourceExperimental — accuracy not yet measured

In the paper

“Only 40% of the genotypes survived and yielded crops (0.3-5.2 g tuber plant -1 ).”

What the sources say

• Supported

  The Results section states that 40% of the assessed genotypes survived under Mars-like soil conditions and had fresh tuber yields of 0.3–5.2 g per plant. This directly supports the cited sentence. (LLM, conf=0.95)

  cites Ramírez et al., 2019 source

In the paper

“For extra-terrestrial farming, it is wellestablished that several simulant properties-such as an alkaline pH, a high availability of sodium, the predominance of macro-vs.micropores, and a scant water holding capacity-can influence plant growth, health, and vigor (Wamelink et al., 2014;Caporale et al., 2020).”

What the sources say

• Partly supported

  The Discussion (page not provided) says that higher water-holding capacity may explain better growth in Mars simulant and that high pH may explain poor growth in moon simulant. The Conclusions likewise identify pH and moisture retention as possible factors. Our copy does not establish high sodium availability or a predominance of macropores over micropores as influences on plant growth. (LLM, conf=0.88)

  cites Wamelink et al., 2014 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Caporale et al., 2020 source

In the paper

“Nevertheless, the Martian simulant outperformed the Lunar simulant in biomass production, as it had trace levels of ammonium nitrate and carbon and no stressors that could cause a higher pH or low water holding capacity.”

What the sources say

• Partly supported

  The Results report higher biomass on the Martian simulant, and the Discussion says its greater water-holding capacity may explain its better performance. Table 2 reports ammonium, nitrate/nitrite, carbon and a lower pH for the Martian simulant than for the lunar one. The paper does not establish that those nutrients caused the biomass difference or that the Martian simulant had no stressors; its explanation is tentative. (LLM, conf=0.87)

  cites Wamelink et al., 2014 sourceExperimental — accuracy not yet measured

In the paper

“For instance, the Martian surface has been found to have a high salt concentration (Ramírez et al., 2019) and high levels of perchlorates (Eichler et al., 2021).”

What the sources say

• Supported

  The citation to Ramírez et al. (2019) is attached to the high-salt-concentration claim, not the perchlorate claim. The Introduction (page not provided) states that Martian regolith is very salty; the discussion of physiological performance also describes salts as important components of Martian regolith. (LLM, conf=0.94)

  cites Ramírez et al., 2019 source
• ?Not checked — no full text of the sourcecites Eichler et al., 2021 source

In the paper

“Although it was a source of nutrients for lettuce, it did not supply organic matter, N, and S, and provided very scant amounts of P.”

What the sources say

• ?Not checked — no full text of the sourcecites Caporale et al., 2020 source
• Supported

  The Discussion states that MMS-1 supplies nutrients including Ca, Fe, Mg and K but lacks organic matter, N, P and S. It also reports that water-soluble phosphate in pure MMS-1 was less than 4% of that in pure compost, supporting the description of its P supply as very scant. (LLM, conf=0.91)

  cites Duri et al., 2020 source

In the paper

“Notably, cabbage and Brussels sprouts exhibited higher absorption of Mn.”

What the sources say

• Supported

  The paper’s abstract says cabbage and Brussels sprouts were particularly efficient at dissolving and absorbing Mn. Its reported measurements also show higher Mn concentrations in lunar-treated seedlings than in untreated seedlings of both species. (LLM, conf=0.94)

  cites Walkinshaw and Johnson, 1971 source

In the paper

“It also lowered the pH of the alkaline simulant, enhanced its cation exchange capacity, organic C and N levels, and the availability of macro-and micronutrients.”

What the sources say

• ?Not checked — no full text of the sourcecites Caporale et al., 2020 source
• Partly supported

  The Discussion (page unavailable) reports greater availability of several nutrients in compost-rich substrates and mentions the cation exchange capacity of compost. It does not report that amendment lowered the simulant’s pH or increased the substrate’s cation exchange capacity, organic C, or N levels; nor does it establish increased availability of micronutrients as a group. (LLM, conf=0.86)

  cites Duri et al., 2020 sourceExperimental — accuracy not yet measured

In the paper

“Plants produce O 2 and fix CO 2 , serve as food for space crews, have a role in water recycling (Maggi and Pallud, 2010;Llorente et al., 2018), and are actively involved in soil structure formation.”

What the sources say

• ?Not checked — no full text of the sourcecites Maggi and Pallud, 2010 source
• Supported

  Section 1 states that plants could supply oxygen, fix carbon dioxide, recycle water, and provide food at extraterrestrial outposts. The citation is attached to the water-recycling clause; the subsequent soil-structure claim is not attributed to this source. (LLM, conf=0.92)

  cites Llorente et al., 2018 source

In the paper

“The red Salanova ® lettuce grown in the 30:70 mixture showed the best crop performance, photosynthetic activity, intrinsic water use efficiency, and quality traits (mineral, carotenoid, and phenolic contents).”

What the sources say

• ?Not checked — no full text of the sourcecites Caporale et al., 2020 source
• Partly supported

  Results §2.1 reports that red Salanova in the 30:70 simulant:compost mixture had the highest fresh yield, net CO₂ assimilation and intrinsic water-use efficiency. But the claim that this mixture also had the best mineral, carotenoid and phenolic contents overstates the findings: Results §2.3 places the highest lutein content in the 70:30 mixture, while Results §§2.2 and 2.4 show that mineral and phenolic contents varied by nutrient or compound, with some highest in 100% compost. (LLM, conf=0.90)

  cites Duri et al., 2020 sourceExperimental — accuracy not yet measured

In the paper

“SiO 2 is the principal constituent in all the simulants.SiO 2 levels are consistently ∼45% in the Lunar simulants, and ∼41% in the Martian ones.”

In the paper

“However, Lunar Highland simulants contain higher levels of anorthite plagioclases than Lunar Mare simulants (59 vs. 34%, respectively).”

In the paper

“Simulants lack key nutrients for plants such as N, which is frequently absent in minerals and occurs in biomolecules.”

In the paper

“Simulants also contain non-negligible amounts of sodium (Lunar: 2.8% of Na 2 O; Martian: 2.4% from Na-plagioclases) and potentially toxic elements (e.g., Cr as Cr 2 O 3 ), which may induce salt or other abiotic stresses in rhizosphere-competent microorganisms and plants (Caporale et al., 2020).”

What the sources say

• ?Not checked — no full text of the sourcecites Caporale et al., 2020 source

In the paper

“Their analysis concluded that the Lunar simulant was the worst in terms of water retention capacity, likely because of its large pore space (0.52 cm 3 cm -3 ) and particle size (0.25-1.0 mm).”

What the sources say

• ?Not checked — no full text of the sourcecites Chamindu Deepagoda et al. (2014) source

In the paper

“On average, compared to Lunar Highland simulants, Lunar Mare simulants are more enriched with mafic minerals (7 vs. 35%, respectively) and oxides (0.2 vs. 2.9%, respectively).”

In the paper

“Lunar and Martian simulants also contain significant levels of other nutrients essential for plant growth.These include potassium (average, 0.9%; 0.7% of K 2 O), phosphorus (0.3%; 0.3% of P 2 O 5 ), sulfur (0.1%; 4.4% of SO 3 ), and manganese (0.1%; 0.1% of MnO), which are derived from K-feldspars, phosphates, sulfates, and Mn oxides, respectively (Figure 1).”

In the paper

“In accordance with the mineralogy of the Lunar dust regolith, the Lunar Dust simulant is enriched by glass and opaque than the Lunar Mare and Lunar Highland simulants (53 vs. 25% and 33%, respectively), and exhibits lower levels of nesosilicates, inosilicates, and tectosilicates (Figure 1; Supplementary Table S2).”

In the paper

“The only data regarding EC in Martian simulants indicate low values of 0.2-0.3dS m -1 (Gilrain et al., 1999;Caporale et al., 2020), suggesting no adverse effect of salinity on plant growth.”

What the sources say

• ?Not checked — no full text of the sourcecites Gilrain et al., 1999 source
• ?Not checked — no full text of the sourcecites Caporale et al., 2020 source

In the paper

“The simulants also contain inorganic carbon in the form of carbonates, and their levels are higher in Martian simulants than in Lunar ones.”

In the paper

“Likewise, Lunar simulants show higher Al 2 O 3 and CaO levels than Martian simulants, whereas the opposite is true for Fe (FeO and Fe 2 O 3 ) and MgO (Figure 2).”

In the paper

“This enhanced the microbial metabolism, promoted faster decomposition of DOC, and much higher emission of NO, N 2 O, N 2 , and CO 2 .”

What the sources say

• ?Not checked — no full text of the sourcecites Maggi and Pallud (2010) source

In the paper

“Based on its hydraulic properties, the 70:30 mixture was best substrate, as the percentage increase in large pores (diameter, 50-120 μm) was more significant in this mixture than in the 30:70 one.”

What the sources say

• ?Not checked — no full text of the sourcecites Caporale et al. (2020) source

In the paper

“Water held in macropores exceeding 120 μm in diameter was not directly beneficial for root water uptake in lettuce (the plant considered in the study), and even caused root asphyxia.”

What the sources say

• ?Not checked — no full text of the sourcecites Caporale et al. (2020) source

In the paper

“Peters et al. (2008) reported that the Martian regolith is classified as a fine-grained and cohesionless rocky soil that is mixed with dust due to planet storms.”

What the sources say

• ?Not checked — no full text of the sourcecites Peters et al. (2008) source

In the paper

“However, these regolith simulants, although not sterile, may play an essential role in improving our understanding of the environmental phenomena on the Moon and Mars.They may also help solve potential problems related to the exploitation of Lunar and Martian regolith as plant growth substrates.”

In the paper

“Potential future challenges include a lack of adequate knowledge about the extra-terrestrial environment and the development of best agronomic practices for the first space colony.”

In the paper

“Due to the lack of a standardized method for evaluating regolith efficacy, many published studies claiming to have assessed regolith for plant growth have used microbiome-contaminated regolith, which is in effect a soil.”

In the paper

“The main critical aspects of space agriculture are presumed to be related to nutrient availability, air and fluid movements in different gravitational conditions, and potentially toxic elements in the substrates.”

In the paper

“Naturally, plant growth, morphology, and physiology on the Moon or other planets are expected to be greatly affected by the sterile and nutrient-poor nature of extra-terrestrial soil and the different gravitational and climatic conditions.”

In the paper

“Potentially toxic elements such as Al and Cr usually precipitate and are poorly available in alkaline environments (Brautigan et al., 2012); therefore, their presence in non-negligible amounts should not hinder plant growth in simulants.”

What the sources say

• ?Not checked — no full text of the sourcecites Brautigan et al., 2012 source

In the paper

“Nevertheless, there is only a minimal quantity of Lunar material on Earth that is closely guarded, and no samples have been brought back from Mars to date.”

In the paper

“Reduced gravity (e.g., in a spacecraft in orbit) causes changes in crucial hydrological variables and alters some fundamental characteristics of water flow and liquid distribution inside a porous medium.”

In the paper

“Perchlorates can be taken up by plants and make their edible parts unsafe to eat.”

In the paper

“The combination of BLSS and ISRU may allow sustainable food production on Moon and Mars.”

In the paper

“Thus, the addition of sustainable amounts of organic amendments (e.g., compost or manure) or mineral fertilizers to Lunar and Martian simulants may enhance the bioavailability of essential nutrients and provide missing vital nutrients such as N and organic C.”

In the paper

“In the absence of rigorous documentation by producers of simulants, this shows the need for an adequate characterization of commercial simulants prior to the designing and planning of any scientific experiments.”

In the paper

“In addition, the Martian regolith sometimes contains toxic perchlorates.”

In the paper

“Furthermore, selected pioneer plants can be grown initially (Kozyrovska et al., 2006) to improve the root zone during cultivation and provide plant residues for humification at the end of their life cycle.”

What the sources say

• ?Not checked — no full text of the sourcecites Kozyrovska et al., 2006 source

In the paper

“The organic waste produced by BLSS crews can help recover compounds and allow their use as fertilizers or compost to support plant growth.”

In the paper

“Furthermore, these simulants generally exhibit numerous features harmful for plant health, such as an alkaline pH, high availability of Na, low cohesion of mineral components, the predominance of macro-vs.micropores, and low water holding capacity.”

In the paper

“However, they lack organic matter and key macronutrients such as N, P, and S.”

In the paper

“To date, Lunar and Martian simulants have been primarily studied for applications other than agronomy (de Vera et al., 2004;Gertsch et al., 2008;Kölbl et al., 2017;Karl et al., 2018), although they have potential use as a substrate for crop growth (Mortley et al., 2000).”

What the sources say

• ?Not checked — no full text of the sourcecites de Vera et al., 2004 source
• ?Not checked — no full text of the sourcecites Gertsch et al., 2008
• ?Not checked — no full text of the sourcecites Mortley et al., 2000 source

In the paper

“In many studies, nutrient deficiency in simulants was overcome by fertigation with nutrient-rich solutions (e.g., Hoagland).”

In the paper

“Although reduced gravity can influence gas and fluid movement, it does not necessarily lead to better rhizospheric conditions.”

In the paper

“At the end of the growth cycle, the authors demonstrated that the first-generation plant residues could serve as a supply of green manure for humification and as a potential nutrient source.”

What the sources say

• ?Not checked — no full text of the sourcecites Kozyrovska et al., 2006 source

In the paper

“Moreover, the chlorophyll and carotenoid concentrations were higher in treated plants, with chlorophyll a being the major pigment present (Weete and Walkinshaw, 1972).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Weete and Walkinshaw, 1972

In the paper

“However, with the addition of nutrients, both plant species grew on JSC-Mars-1A and MMS, but did not grow on MGS-1.”

What the sources say

• ?Not checked — no full text of the sourcecites Eichler et al., 2021 source

In the paper

“Plants grown in compost:simulant ratios of 1:0, 3:1, and 1:1 showed yields that were greater than those in the 1:3 and 0:1 ratios, and control plants irrigated with only water produced similar trends.”

What the sources say

• ?Not checked — no full text of the sourcecites Gilrain et al., 1999 source

In the paper

“Lunar and Martian soils lack organic matter and biotic activity (Seiferlin et al., 2008), although there is some evidence of a biofilm (Thomas-Keprta et al., 2014;Eigenbrode et al., 2018).”

What the sources say

• ?Not checked — no full text of the sourcecites Seiferlin et al., 2008 source

In the paper

“The authors noted the absence of disease agents in the plants tested under experimental conditions, and concluded that the Lunar material could potentially support the growth of a wide range of plant species.”

What the sources say

• ?Not checked — no full text of the sourcecites Walkinshaw et al., 1970 source

In the paper

“As reported in Section 2.2, plants need macro and micronutrients for optimal growth, and these can be found in both inorganic and organic forms in soil on Earth (Hopkins and Huner, 2008;Fageria, 2009).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hopkins and Huner, 2008
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fageria, 2009

In the paper

“Therefore, the authors concluded that both simulants showed potential for use as a substrate for crop production.”

What the sources say

• ?Not checked — no full text of the sourcecites Aglan et al., 1998 source
• ?Not checked — no full text of the sourcecites Mortley et al., 2000 source

In the paper

“The authors concluded that cultivation on Mars would require less water for irrigation and lower external nutrient supply than on Earth.”

What the sources say

• ?Not checked — no full text of the sourcecites Maggi and Pallud (2010) source

In the paper

“The literature review showed that pure regolith simulants may be suitable media for plant growth (at least for limited periods) and function as a source of essential nutrients such as K, Ca, Mg, and Fe.”

In the paper

“The first solution involves the use of a stable organic amendment, not only as a supply of organic carbon, but also to improve the physical features of regolith (Gilrain et al., 1999).”

What the sources say

• ?Not checked — no full text of the sourcecites Gilrain et al., 1999 source

In the paper

“Thus, Lunar and Martian soils (and, therefore, regolith simulant-based substrates) are potentially deficient in all macro-and micronutrients, which are derived exclusively (N), mostly (P, S), or partly (K, Ca, Mg, Fe, Zn, Cu, Mn, B, Cl, and Ni) from the degradation of organic components.”

In the paper

“The authors concluded that the compost mainly promoted plant growth by improving the physical features of the regolith that regulate water and/or nutrient availability.”

What the sources say

• ?Not checked — no full text of the sourcecites Gilrain et al., 1999 source

In the paper

“In these tests, the simulants mainly provided mechanical anchorage for the plant roots, and did not cause any adverse or toxic effects in the plants.”

What the sources say

• ?Not checked — no full text of the sourcecites Aglan et al., 1998 source
• ?Not checked — no full text of the sourcecites Mortley et al., 2000 source

In the paper

“Carbon is absorbed from the atmosphere through photosynthesis (Hopkins and Huner, 2008), and organic matter is the primary source of both N and P.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Hopkins and Huner, 2008

In the paper

“Calcium perchlorate-enriched simulants were unable to sustain plant growth, even with nutrient supply.”

What the sources say

• ?Not checked — no full text of the sourcecites Eichler et al., 2021 source

In the paper

“However, this agronomic technique is not feasible and sustainable in space agriculture, as the nutritional resources must be carried from the Earth and cannot be produced in BLSS.”

In the paper

“Although this may be feasible for microgreens or salad crops, it is more challenging for other candidate species such as potato (a source of carbohydrates) and soybean (a source of proteins), which require more nutrients and resources to produce a sufficiently edible yield than do salad crops.”

In the paper

“In extra-terrestrial soil, water dynamics would regulate the extent of mineral weathering and the rate of organic matter decomposition, thus greatly affecting the biogeochemistry and bioavailability of nutrients and plant growth.”

In the paper

“In sustainable scenarios of space farming, regolith-based substrates are required to sustain plant growth throughout the plant life cycle, including the complete seed maturation needed for reproduction.”

In the paper

“Providing ecosystem services by using a regolith-based substrate might be the key to a fruitful and sustainable Lunar or Martian BLSS.”

In the paper

“Thus, further steps-such as water rinses, phytoremediation, volatilization, and chemical reduction by using perchlorate-reducing bacteria-are necessary to make Mars regolith a viable growing substrate.”

In the paper

“The presence of-and interactions with-biota (including pathogens, cyanobacteria, plant growth-promoting bacteria, beneficial symbiotic fungi, and worms) and biostimulants will add further complexity to life support systems with extraterrestrial soils.”

In the paper

“This can lower the substrate pH, increase mineral weathering rates, enhance nutrient release/availability, promote the aggregation of particles of different sizes (to form a more efficient porous system), and overall contribute to soil improvement.”

In the paper

“The occurrence of perchlorates in the Mars regolith provides a significant challenge to its use as an agricultural substrate.”