University of Manchester scientists have created a new material, dubbed ‘StarCrete’ which is made from extra-terrestrial dust, potato starch, and a pinch of salt and could be used to build homes on Mars.

Building infrastructure in space is currently prohibitively expensive and difficult to achieve. Future space construction will need to rely on simple materials that are easily available to astronauts, StarCrete offers one possible solution.

The scientists behind the invention used simulated Martian soil mixed with potato starch and a pinch of salt to create the material that is twice as strong as ordinary concrete and is perfectly suited for construction work in extra-terrestrial environments.

In an article published in the journal Open Engineering, the research team demonstrated that ordinary potato starch can act as a binder when mixed with simulated Mars dust to produce a concrete-like material.

When tested, StarCrete had a compressive strength of 72 Megapascals (MPa), which is more than twice as strong as the 32 MPa seen in ordinary concrete. Starcrete made from moon dust was even stronger at more than 91 MPa.

Comparison of proposed ISRU technologies for the stabilisation of extraterrestrial regolith into solid materials. Ultimate compressive strength (UCS) range of materials plotted against the proportion of material required beyond unprocessed regolith. Purple, yellow and green colours indicate high-, medium- and low-energy processes, respectively. Figure adapted from Karl et al.

This work improves on previous work from the same team where they used astronauts’ blood and urine as a binding agent. While the resulting material had a compressive strength of about 40 MPa, which is better than normal concrete, the process had the drawback of requiring blood on a regular basis. When operating in an environment as hostile as space, this option was seen as less feasible than using potato starch. 

'Since we will be producing starch as food for astronauts, it made sense to look at that as a binding agent rather than human blood. Also, current building technologies still need many years of development and require considerable energy and additional heavy processing equipment which all adds cost and complexity to a mission. StarCrete doesn’t need any of this and so it simplifies the mission and makes it cheaper and more feasible.' Dr Aled Roberts

“Since we will be producing starch as food for astronauts, it made sense to look at that as a binding agent rather than human blood. Also, current building technologies still need many years of development and require considerable energy and additional heavy processing equipment which all adds cost and complexity to a mission. StarCrete doesn’t need any of this and so it simplifies the mission and makes it cheaper and more feasible. And anyway, astronauts probably don’t want to be living in houses made from scabs and urine,” says Dr Aled Roberts, research fellow at the Future Biomanufacturing Research Hub, the University of Manchester and lead researcher for this project.

The team calculate that a sack (25 Kg) of dehydrated potatoes (crisps) contain enough starch to produce almost half a tonne of StarCrete, which is equivalent to more than 213 bricks worth of material. For comparison, a three-bedroom house takes roughly 7,500 bricks to build. 

Scheme depicting the steps taken to produce StarCrete.

Additionally, they discovered that a common salt, magnesium chloride, obtainable from the Martian surface or from the tears of astronauts, significantly improved the strength of StarCrete.

The next stages of this project are to translate StarCrete from the lab to application. Dr Roberts and his team have recently launched a startup company, DeakinBio, which is exploring ways to improve StarCrete so that it could also be used in a terrestrial setting.

If used on Earth, StarCrete could offer a greener alternative to traditional concrete. Cement and concrete account for about 8% of global CO₂ emissions as the process by which they are made requires very high firing temperatures and amounts of energy.

StarCrete, on the other hand, can be made in an ordinary oven or microwave at normal ‘home baking’ temperatures, therefore offering reduced energy costs for production. 

Stress–strain profiles for Martian (MGS-1) and lunar (LHS-1) Starcrete undergoing (a) uniaxial compression tests and (b) three-point flexural tests. (c) and (d) Camera images Martian and lunar Starcrete, respectively. (e) and (f) SEM images of Martian and lunar Starcrete, respectively. Scale bars = 20 µm.

Abstract conclusions and outlook 

The study has been published in the journal Open Engineering, and its conclusions and outlook are as follows: 

Future habitats on the lunar and Martian surfaces will need robust and affordable technology capabilities to produce substantial quantities of construction materials in situ.

In this work, we demonstrate that ordinary plant-derived starch can serve as an effective binder for extraterrestrial regolith to produce ERBs with compressive strengths within the domain of high-strength concrete (>42 MPa).

The advantages of StarCrete over other proposed technology options include the following:

• Risk reduction: having an edible binder means it could be consumed in the event of an ‘Apollo 13’ type emergency where the ship or habitat enters ‘lifeboat mode’;
• Practicality: unlike many other proposed technology options, StarCrete is a relatively simple solution with a high technology readiness;
• System integration: the production of starch could be integrated with food and oxygen production systems (ie, plant growth), simplifying mission architecture and lowering costs;
• Resourcefulness: unlike many other technology options, starch production doesn’t require high energy processing, and most water can be recovered since the mechanism is driven by dehydration;
• Resource locality: starch will be produced on-site, which is an advantage over some other technology options that would require mining and transportation of sparse mineral deposits; and
• Architectural flexibility: being an exceptionally high-strength material, habitats can be designed with fewer architectural constraints.

Although StarCrete displays significant potential as an extraterrestrial construction material, further studies will be needed to evaluate its full potential and limitations.

Avenues for future work

1. Screening a broader range of starch sources and additives
2. Further investigation into the bonding mechanism and adhesion strength of the starch binder with regolith
3. Further testing of StarCrete under simulated off-world conditions (ie, repeated thermal swings, high radiation, and low pressure) with a focus on durability and longevity of the materials
4. Hypervelocity impact testing to evaluate resistance to meteor strikes
5. Regolith particle size optimisation
6. Tailoring the biosynthesis of starch for further optimisation (eg, directed evolution of the gene corresponding to starch synthase), and
7. Investigating the potential of StarCrete for additive manufacturing (3D printing). Also, since starch granule formation in plants is dependent on various environmental conditions, such as sunlight exposure and circadian rhythms, plants grown under reduced gravity and controlled lighting could form differently from those grown on Earth and hence produce StarCrete with differing properties – therefore, validation of the results under expected operating conditions would be needed before its practical application.

Finally, it is worth noting that since cement and concrete account for about 8% of global CO₂ emissions, further development of StarCrete could result in a relatively sustainable alternative for Earth-based construction.

For this to be achieved, the moisture-sensitivity of starch binder needs to be overcome. This could be achieved through the incorporation of covalent cross-linking agents, heat-induced cross-linking, or other biopolymer additives such as proteins, waxes, or terpene-based resins.