Enlarge /. Scientists mixed chitin – an organic polymer found in abundance in both arthropods and fish scales – with a mineral that mimics the properties of Martian soil to create a viable new material for building tools and shelters on Mars.
Space lovers who dream of one day colonizing Mars must grapple with the reality of the planet's limited natural resources, especially when it comes to building materials. A team of scientists from the Singapore University of Technology and Design discovered that the organic polymer chitin, found in the exoskeleton of insects and crustaceans, can be easily converted into a viable building material for basic tools and habitats using simple chemistry. This would require minimal energy consumption and no transport of special equipment. The scientists described their experiments in an article recently published in the journal PLOS ONE.
"The technology was originally developed to create circular ecosystems in urban environments," said co-author Javier Fernandez. "However, because of its efficiency, it is also the most efficient and scalable method for producing materials in a closed artificial ecosystem in the extremely scarce environment of a lifeless planet or satellite."
As we previously reported, NASA has announced an ambitious plan to bring American astronauts back to the moon and establish a permanent base there to eventually place astronauts on Mars. Materials science will be vital to the success of the Artemis Moon program, especially when it comes to the materials needed to build a viable Moon (or Martian) base. For example, concrete requires a significant amount of added water to be used on site, and there is a marked water shortage on both the Moon and Mars. And the transport costs would be prohibitively high. NASA estimates that it would cost around $ 10,000 to transport just a pound of material into orbit.
Therefore, much attention has been paid to the possibility of using existing materials on the moon itself to build a moon base. Previous proposals called for 3D printing with Sorel cement, which requires significant amounts of chemicals and water (consumables), and a stone-like material that requires both water and phosphoric acid as a liquid binder. And back in March, an article by an international team of scientists suggested that astronauts building a base on the moon could use the urea in their urine as a plasticizer to turn lunar soil into a concrete-like building material.
As with the moon, any plan to build a habitable base on Mars must employ manufacturing technologies that take advantage of the red planet's regolith. However, the authors of the current paper suggest that most terrestrial manufacturing strategies that could fit into the bill typically require specialized equipment and a lot of energy. "However, nature presents successful life strategies that adapt to harsh environments," the authors wrote. Rigid structures are formed in biological organisms by integrating inorganic fillers that come from the environment with low energy costs (e.g. calcium carbonate) and are incorporated into an organic matrix (e.g. chitin) that are produced at relatively high metabolic costs becomes.
Enlarge /. Creating a model with a 3D printed lander module shows a possible scenario for creating habitats on Mars.
N. Shiwei, S. Dritsas, J.G. Fernandez / PLOS ONE
Fernandez and colleagues claim that chitin is likely part of a planned artificial ecosystem because it is so abundant in nature. For example, it is the main component of fish scales and fungal cell walls, as well as the exoskeleton of crustaceans and insects. In fact, insects have already been selected as a key source of protein for a possible Mars base. And since the chitin component of insects has limited nutritional value to humans, extraction into building materials "cannot hinder or compete with the food supply," the authors wrote. "Rather, it's a by-product of that."
For their experiments, the researchers relied on fairly simple chemistry. They took chitosan extracted from shrimp, dissolved it in acetic acid – a common by-product of aerobic and anaerobic fermentation – and combined it with a mineral equivalent to Martian soil to make their building material, which contains chitin. They tested its properties by making various objects out of it, in particular a function key, which they tested by tightening a hexagonal screw. While it was recognized that this was unlikely to replace metallic tools for certain critical space applications, it was found to be robust enough to maintain sufficient torque for small daily tasks.
Next, the team tried to shape the material into various geometries to explore its potential as a building material through additive manufacturing. It ranged from cylinders and cubes to objects with rounded and angular shapes – including a small humanoid Mars figure. The scientists also showed that the Biolith can be used as a makeshift mortar to effectively plug a small hole in a pipe. The pipe then ran for several weeks without any leakage. Eventually, they built a full 3D-printed model of a possible blueprint for a Martian habitat. It took just under two hours to complete. The researchers concluded that their results demonstrated the feasibility of such "closed-loop, waste-free" solutions on Mars.
"Bio-inspired manufacturing and sustainable materials are not a replacement technology for synthetic polymers, but rather a technology that defines a new paradigm in manufacturing and enables things to be done that their synthetic counterparts cannot," said Fernandez. "We have shown that they are critical not only to our sustainability on Earth, but also to one of the next greatest achievements of humankind: our transformation into an interplanetary species."
DOI: PLOS ONE, 2020. 10.1371 / journal.pone.0238606 (About DOIs).