“Blood, Sweat, and Tears: Extraterrestrial Regolith Biocomposites With in Vivo Binders”, A. D. Roberts, D. R. Whittall, R. Breitling, E. Takano, J. J. Blaker, S. Hay, N. S. Scrutton2021-09 (, )⁠:

The proverbial phrase ‘you can’t get blood from a stone’ is used to describe a task that is practically impossible regardless of how much force or effort is exerted. This phrase is well-suited to humanity’s first crewed mission to Mars, which will likely be the most difficult and technologically challenging human endeavor ever undertaken. The high cost and large time delay associated with delivering payloads to the Martian surface means that exploitation of resources in situ—including inorganic rock and dust (regolith), water deposits, and atmospheric gases—will be an important part of any crewed mission to the Red Planet. Yet there is one important, but chronically overlooked, source of natural resources that will—by definition—also be available on any crewed mission to Mars: the crew themselves.

In this work, we explore the use of human serum albumin (HSA)—a common protein obtained from blood plasma—as a binder for simulated Lunar and Martian regolith to produce so-called ‘extraterrestrial regolith biocomposites (ERBs).’ In essence, HSA produced by astronauts in vivo could be extracted on a semi-continuous basis and combined with Lunar or Martian regolith to ‘get stone from blood’, to rephrase the proverb.

Employing a simple fabrication strategy, HSA-based ERBs were produced and displayed compressive strengths as high as 25.0 MPa. For comparison, standard concrete typically has a compressive strength ranging 20–32 MPa.

The incorporation of urea—which could be extracted from the urine, sweat, or tears of astronauts—could further increase the compressive strength by over 300% in some instances, with the best-performing formulation having an average compressive strength of 39.7 MPa. Furthermore, we demonstrate that HSA-ERBs have the potential to be 3D-printed, opening up an interesting potential avenue for extraterrestrial construction using human-derived feedstocks.

The mechanism of adhesion was investigated and attributed to the dehydration-induced reorganization of the protein secondary structure into a densely hydrogen-bonded, supramolecular β-sheet network—analogous to the cohesion mechanism of spider silk. For comparison, synthetic spider silk and bovine serum albumin (BSA) were also investigated as regolith binders—which could also feasibly be produced on a Martian colony with future advancements in biomanufacturing technology.

[Keywords: human serum albumin hybrid materials, in situ resource usage, biopolymer-bound soil composites, recombinant spider silk, 3D-printing]

Figure 2: Scheme depicting the typical fabrication procedure for producing HSA-based ERBs.
Table 1: Comparison of the mechanical properties and processing energy requirement of several other regolith stabilization technologies, including primary disadvantages of each technique. Note that quantitative data for processing energy requirements were not available for all sources, so qualitative data (low/medium/high) were presented in these instances.
Method UCS (MPa) Processing energy (kWh/MT) Primary disadvantages Refs.
Melted and cast regolith 550 360 (very high) Extremely high processing energy and temperature (1,200–1,500℃) [7,20]
Sintered regolith 14.5 156 (high) High processing energy and temperature (1,000–1,200℃) 7,20,21
Extraterrestrial concrete 75.5 High High processing energy and water consumption. Geographically sparse precursors 7
Sulfur-bound regolith 30 High High processing energy. Susceptible to sublimation 7,20
Sand-bagging 2 Low Poor mechanical properties. Ex situ bags needed 20
ERBs with BSA 19.5 Low Bringing cows to Mars is not feasible with current technology This study,20
ERBs with HSA 25.0 Low Limited production. Potentially detrimental to crew wellbeing This study
ERBs with HSA and urea 39.7 Low Limited production. Potentially detrimental to crew wellbeing This study
ERBs with synthetic spider silk N/A Low/Medium Low technology readiness This study
ERBs with natural spider silk N/A Low Spiders are difficult to farm for silk —

…The remarkably high compressive strength of HSA-ERBs—which could be fabricated with minimal ex situ components without any heavy, malfunction-prone in situ binder production equipment—certainly warrants further investigation. We note that there is substantial scope for improvement of material properties, too, with many factors such as curing temperature, compacting, and method of binder infusion having yet to be optimized. A large amount of formulation optimization could also improve properties, such as pH and ionic conditions, or the inclusion of other in vivo substances such as feces, human hair, mucus, or other bodily fluids into the formulation.