A lichen that grows like powder dusted on a rock. Image by Tigerente Own work, CC BYSA 3.0
NASA’s next phase of space exploration includes a human settlement on Mars. The costs and logistics are immense. One area where costs can be reduced is with construction. Instead of transporting all the construction materials from Earth to the red planet, using Martian soil to construct a site on Mars is seen by many scientists as the optimal approach.
Primarily, this involves finding a means to produce sulphur concrete, a material of a potential strength to be similar or higher levels of conventional Earthbased cementitious concrete.
Synthetic lichen system
A new selfgrowing technology carries the ability to assist future colonists with Martian architecture by using living biomaterials to 3D print structures. This is based on a new synthetic lichen system which uses fungi and bacteria to grow building materials directly from Martian soil. Moreover, this could occur autonomously and without human intervention.
Natural lichen is composed of algae or cyanobacteria living symbiotically with fungi. Lichens have properties different from those of their component organisms. They come in many colours, sizes, and forms and are sometimes plantlike, but are not plants.
The technology is being researched at Texas A&M University and the University of NebraskaLincoln. Here researchers have used biomanufacturing engineered living materials as part of the NASA Innovative Advanced Concepts programme. The basis of the technology is to exploit the planet’s regolith (loose, fragmented surface material such as dust, sand and rocks). This is to provide the technological basis to build in the most demanding environments with restricted resources.
A variety of methods for bonding Martian regolith particles have previously been applied, including magnesiumbased, sulphurbased, and a geopolymer creations. However, all such methods require significant human assistance and are generally regarded as unfeasible due to the expected lack of human resources on Mars.
This has led other research approaches to consider microbemediated selfgrowing technology. Various designs have been developed, such as bacterial biomineralization to bind sand particles into masonry, ureolytic bacteria to promote the production of calcium carbonate to make bricks, and an exploration of the use of fungal mycelium as a bonding agent.
While this microbemediated selfgrowing technology is very promising, the current practices are not completely autonomous since the microbes being used are limited to a single species or strain. This means that their survivability requires a continuous supply of nutrients, meaning outside intervention is needed.
The Texas A&M approach uses a synthetic community, making use of the advantages of multiple species. This system eliminates the need for external nutrient supplies. This design uses heterotrophic filamentous fungi as bonding material producers. The organisms can promote large amounts of biominerals as well as being able to survive harsh conditions. These fungi are paired with photoautotrophic diazotrophic cyanobacteria to create a synthetic lichen system.
Sulphurbased concrete
The diazotrophic cyanobacteria fix carbon dioxide and dinitrogen from the atmosphere and convert them into oxygen and organic nutrients to help the survival and growth of filamentous fungi as well as increasing the concentration of carbonate ions by photosynthetic activities.
The filamentous fungi bind metal ions onto fungal cell walls and serve as nucleation sites for biomineral production, as well as enhance the growth of cyanobacteria by providing them water, minerals, and carbon dioxide. Both components secrete biopolymers that enhance the adhesion and cohesion among Martian regolith and precipitated particles to create a consolidated body. Because the system grows with only Martian regolith simulant, air, light and an inorganic liquid medium, no human intervention is required.
Mycelial materials are currently commercially produced, known for creating insulators and fire retardant.
Studies have shown how these coculture systems display robust growth solely based on Martian regolith simulants, air, light, and an inorganic liquid medium without any additional carbon or nitrogen sources.
The research appears in the Journal of Manufacturing Science and Engineering, with the research paper titled “BioManufacturing of Engineered Living Materials for Martian Construction: Design of the Synthetic Community.”
