As NASA sets its sights on an eventual mission to Mars, scientists are trying to solve some of the practical challenges such an endeavor will present. Researchers now believe they’ve solved one of the issues—building and tool manufacturing—by relying on the second most abundant organic polymer on Earth.
This plentiful material, which is only surpassed by cellulose in terms of Earth-based organic polymers, is known as chitin. It is found not only in the shells of insects but also in crustaceans and fish scales and the cellular walls of mushrooms.
Researchers at the Singapore University of Technology and Design were looking for ways to use the material to create a closed-loop ecosystem in cities, in which easily accessible organic materials are used in manufacturing and then returned to the environment when their lifespan is over. Instead, they found a way to apply the same thinking to life in outer space.
“The technology was originally developed to create circular ecosystems in urban environments, but due to its efficiency, it is also the most efficient and scalable method to produce materials in a closed artificial ecosystem in the extremely scarce environment of a lifeless planet or satellite,” said lead researcher Javier Fernandez.
Shrimp to the Rescue!
To see if chitin could be used as a building material on a someday Mars colony, the researchers obtained it from shrimp shells treated with sodium hydroxide—a compound, they say, which could be obtained on Mars using electrolytic hydrolysis, a process involving the splitting of water molecules and the use of those molecules to split other compounds.
This procedure produced chitosan, the usable fiber from the shells. This was then dissolved in acetic acid, which could be made on Mars through a simple fermentation process. Finally, the solution was combined with a simulant of Martian soil to produce the building material, known as a biolith. In a paper describing the work, which has been published in the peer-reviewed journal PLOS ONE, researchers point out that while the chemicals needed to produce the biolith could be easily made on Mars, the process would be even more straightforward —and require even fewer steps and compounds—if the chitosan was produced from the production of fungi.
“The pH-based, simplified chemistry used here for the extraction and manufacture of chitosan requiring only water (available in the form of subsurface ice), sodium hydroxide, and acetic acid, can be further simplified if the polymer is obtained from an ecosystem involving fungi and, therefore, not requiring deacetylation/NaOH, or can be avoided completely by the use of enzymatic fractionation,” they write in their paper.
Eat Your Insects, Then Build Things with Them!
In either case, the fact that edible material—including insects, which have already been discussed as a potential food source for Mars pioneers—can be turned into more stable building material, creates the circular ecosystem ideally suited for a mission in which every item will contribute weight and cost.
To test out their material, the researchers created a wrench that was able to withstand impressive torque. The fact that it did fail after enough force was applied could be a benefit; the researchers say that such tools could be designed to fail at specific force loads to prevent overtightening of bolts.
The biolith was also used to create a model of a Mars habitat, which was based on the winner of NASA’s 3D-printed Mars Habitat Challenge as well as a small Martian figurine.
In their paper, the researchers say that their chitosan compound could also be used to produce bioplastics for such things as cups and cutlery and wound dressings, and geotechnical applications such as dust control and soil stabilization. Once any chitosan-based product reaches the end of its life, it could easily be recycled and used again.
“Against the general perception, bioinspired manufacturing and sustainable materials are not a substituting technology for synthetic polymers, but an enabling technology defining a new paradigm in manufacturing and allowing to do things that are unachievable by the synthetic counterparts,” said Fernandez. “Here, we have demonstrated that they are key not only for our sustainability on Earth but also for one of the next biggest achievements of humanity: our transformation into an interplanetary species.”