Biomining Research In Space

Introduction

In our previous article, we explored the potential of CRISPR gene editing technology in space biomining applications. CRISPR’s ability to modify genetic material in a desired direction is considered a promising solution in the field of space mining.

This technology can improve biomining processes by enhancing the ability of microorganisms to adapt to the harsh conditions of space, and can make the processing of mineral resources in space more efficient.

The purpose of this article is to provide a more detailed analysis of how biomining applications can be used.

What is Biomining in Space ?

Space mining refers to the extraction of valuable minerals from extraterrestrial planets and space materials. The potential depletion of mineral reserves on Earth has motivated people to seek such raw materials within the solar system.

Technological advancements have increased the importance of strategies for processing and utilizing minerals identified in space that are critical on Earth. For example, while it is considered to transport metals such as gold, silver, copper, and platinum to Earth; it is planned to use iron group metals, cobalt, and titanium elements in space structures.

In this context, biomining stands out as a process in which microorganisms are used to extract and recover valuable metals from minerals and waste. This method offers a significant alternative in terms of both environmental sustainability and economic efficiency.

Biomining Studies in Space

There is currently insufficient knowledge about space biomining. The differences between Earth and space environments may limit the direct applicability of existing biomining methods to space conditions. Therefore, new and comprehensive research is being conducted to examine in detail the effects of space environments on biomining.

One of the most relevant applications of space biomining is in-situ resource utilization (ISRU). Bio-ISRU specifically refers to the use of biotechnology to enable the processing of resources from planets. In-situ resource utilization (ISRU) approaches aim to enable sustainable space exploration and settlement by reducing the need to supply materials and products from Earth.

While biomining offers many advantages compared to classical methods on Earth, the conditions in space and the available rock materials differ from the biomining materials commonly used on Earth.

Asteroids with biomining potential are either near-Earth objects or in the asteroid belt beyond the orbit of Mars. Near-Earth objects may be more suitable for lunar settlements or return to Earth, while objects from the asteroid belt can be used for Mars settlements.

Principles of Space Biomining

When it comes to space biomining and in-situ resource utilization (ISRU), three fundamental questions need to be answered:

1. Which elements need to be obtained for a specific application?
2. In which regions can we discover these elements?
3. Which mining method works most effectively, and in some cases, may exclude biomining? (Berliner et al. 2021).

To answer the first question, the elements that are important for space biomining can vary depending on the purpose (Cockell 2011; Raafat et al. 2013). In general, the elements and compounds that are important for establishing human settlements are: water, molecular oxygen, essential mineral nutrients, gaseous volatiles (hydrogen, carbon, nitrogen, helium), structural metals (iron, copper, nickel, vanadium), and silicon and rare earth elements required for electronic devices (Menezes et al. 2015).

Space Conditions and Their Impact on Biomining

Space conditions differ significantly from those on Earth, and these differences greatly affect biomining processes. These differences include factors such as pressure, temperature, radiation, and microgravity. In particular, the growth, survival, resilience, and biofilm formation of microorganisms in space environments are affected by these conditions, and the consequences of these effects are not yet fully understood. To understand how biomining processes work in space, it is crucial to examine the specific conditions in different space environments such as Mars, the Moon, and asteroids.

In the context of biomining applications on the Martian and lunar surfaces, rare earth elements and vanadium have been extracted from rocks simulating Mars and the Moon using organotrophic bacteria (Sphingomonas desiccabilis and Bacillus subtilis) (Cockell et al. 2020, 2021).

These microorganisms can recover metals from low-sulfur minerals and have been observed to play a successful role in Mars gravity and microgravity conditions on the International Space Station.

Many toxic components can hinder biomining and settlement on the Lunar and Martian surfaces. Perchlorates on Mars (a strong oxidizer) (Hecht et al. 2009; Kounaves et al. 2014) and toxic lunar dust (Linnarsson et al. 2012) are examples of this.

The ability of biomining microorganisms to make these components less toxic or eliminate them altogether highlights the importance of bioremediation approaches (the process of cleaning up pollution using microorganisms). Bioremediation properties of biomining microorganisms are used to eliminate or make toxic components less harmful.

Synthetic biology and biotechnological techniques can improve the resistance of microorganisms to toxic components and enhance metal extraction.

For example, Deinococcus radiodurans, a microorganism resistant to extreme conditions, has been bioengineered to increase its bioremediation capacity (Daly 2000). While bioengineering can enhance desired traits or reduce unwanted effects, the success of these engineering approaches depends on the resistance of microorganisms to genetic manipulation.

In space biomining, regolith and rocks can provide bioavailable water, oxygen, hydrogen, carbon, sulfur, etc. These processes involve chemical reactions similar to bioremediation methods used to clean up toxic components on Earth.

Extremophiles and polyextremophiles that can live in extreme conditions can be beneficial in space conditions.

Microorganisms with the ability to bioaccumulate and bioremediate toxic components in the harsh conditions of Mars and the Moon can be used for purposes on Earth or can inform us about how to achieve similar goals.

Most biomining on Earth is based on autotrophic microorganisms that can break down sulfide minerals without requiring carbon components, and many rocks in the Solar System have low sulfur content.

Therefore, heterotrophic microorganisms that require organic components may be a better choice in such cases. Careful selection of the most suitable techniques or microorganisms is necessary for a specific application (Averesch 2021).

In conclusion, understanding the effects of space conditions on biomining and bioremediation is important to investigate the use of synthetic biology to overcome the limitations of bioleaching mechanisms.

While ethical and planetary protection discussions are beyond the scope of this review, these factors should be considered in planning mining and in-situ resource utilization (ISRU) for a planet or region.

Space Biomining Experiments

Among the experiments conducted on space biomining, the BioRock and BioAsteroid experiments conducted on the International Space Station (ISS), as well as the preparatory goal for BioRock, are noteworthy.

These experiments demonstrated for the first time the feasibility of conducting space biomining using heterotrophic microorganisms (bacteria and fungi) and substrates such as basalt or meteorites.

In 2007, NASA’s lunar regolith biomining study suggested the potential of microorganisms to extract metals and other resources from lunar materials, and this idea has been supported and developed by subsequent research.

In particular, studies using the model biomining bacterium Acidithiobacillus ferrooxidans have investigated the extraction of metals from simulated lunar and Martian regolith. These studies have shown that microgravity directs the biosynthesis of intracellular nanoparticles in A. ferrooxidans cells grown under anaerobic conditions. Electron microscopy observations suggest that A. ferrooxidans has the potential to produce metal bioleach and useful nanoparticles in space (Kaksonen et al. 2021).

It has been suggested that these microorganisms can be engineered as synthetic biological “microfactories” to convert target planetary resources into useful products in situ. Additionally, A. ferrooxidans has been observed to grow anaerobically and dissolve metals from simulated lunar and Martian regolith models composed of oxides under modeled microgravity conditions.

Different performances were observed compared to biotic dissolution depending on the type of metal, and intracellular magnetite biosynthesis increased. This has revealed the potential of A. ferrooxidans to develop nanoparticles in space (Kaksonen et al. 2021).

Fungi can also produce various organic acids for biomining processes. This process is known as bioleaching and is based on chemical interactions between organic acids and rocks where metal elements are found in oxide form.

Metal extraction occurs following chemical reactions such as acidolysis and complexolysis (Dusengemungu et al. 2021). Although fungi have the ability to process a wider variety of substrates compared to bacteria, their need for a continuous organic carbon source can significantly increase costs compared to bacterial methods.

MELiSSA (Micro-Ecological Life Support System Alternative) Experiment

Waste products resulting from human activities on a space station can provide the necessary organic carbon for microorganisms. This opportunity has been considered by the European Space Agency (ESA) and biomining has been included in the MELiSSA (Micro-Ecological Life Support System Alternative) project.

Designed as an innovative network for space exploration, MELiSSA is based on regenerative systems aimed at producing food, water, and oxygen from waste generated during a mission. In this context, biomining can be used to extract metals from regolith and can also contribute to the sustainability of a crew on a spacecraft (Lasseur and Mergeay 2021).

BioRock Experiment

In 2019, the European Space Agency (ESA) conducted the BioRock experiment on the International Space Station (ISS), investigating the bioleaching processes of basalt rock and the effects of these processes on different gravity conditions. The primary objective of the experiment was to assess the potential of extracting economically important elements, especially rare earth elements, from basalt rock, a proxy for lunar and Martian regolith materials, using microorganisms.

The experiment compared the effectiveness of three different heterotrophic bacterial species in dissolving basaltic rock under microgravity, simulated Mars gravity, and Earth gravity conditions. These microorganisms were Sphingomonas desiccabilis, Bacillus subtilis, and Cupriavidus metallidurans. The research results showed that these bacterial species, especially S. desiccabilis, demonstrated the ability to successfully dissolve rare earth elements under different gravity conditions.

It was observed that Sphingomonas desiccabilis increased the average extracted concentration of rare earth elements under all gravity conditions, indicating that the bacterium provided a significant increase in yield compared to non-biological control samples under all gravity conditions, including microgravity. However, no statistically significant difference was found in the dissolution role between microgravity and other gravity simulations. This suggests that the effect of microgravity on bioleaching is limited and the processes are specific to the microorganisms.

The ability of S. desiccabilis to extract rare earth elements and vanadium under different gravity conditions on the International Space Station has been demonstrated. This is the first time that the biomining capacity of S. desiccabilis has been proven, and this discovery offers an innovative development for applications on Earth. The development of strains for extracting elements from low-grade ores and extreme conditions can contribute to the development of biomining technologies that can also be used on Earth for similar purposes.

On the other hand, biological experiments conducted with Bacillus subtilis and Cupriavidus metallidurans did not show a significant difference compared to the Earth gravity simulation, but a significant increase was observed compared to non-biological control samples in experiments with S. desiccabilis. This indicates that S. desiccabilis, in particular, can effectively perform bioleaching regardless of gravity conditions.

S.desiccabilis and Cupriavidus metallidurans were observed to form positive biofilms on the rock surface under three different gravity conditions: microgravity, simulated Mars gravity, and Earth gravity. Additionally, it was found that S. desiccabilis and B. subtilis increased the dissolution rate of vanadium compared to sterile control cultures under these gravity conditions.

In conclusion, the data from the BioRock experiment has revealed the potential of bioleaching in space and how this potential can be effective under different gravity conditions. The bioleaching ability of S. desiccabilis is a promising discovery, especially for extracting elements from asteroids and other low-gravity planetary objects in low-gravity environments. This experiment can create a critical foundation for the development of bioleaching technologies for extracting elements from low-grade ores and extreme conditions on Earth.

Figure-1. Sphingomonas desiccabilis, one of the three microbes selected for the BioRock experiment, was observed growing on basalt. (Image Credit: UK Centre for Astrobiology/University of Edinburgh-Rosa Santomartino)

Figure-2. BioRock Experimental Unit (Cockell et al. 2020). (IMage Credit: ESA, NASA)

a. A top-view of an experimental unit within an experimental container shows that both culture chambers are filled with growth medium.

b. A cross-sectional view of the culture chamber shows the position of the basalt rock at the back and how the growth medium was injected and the membrane was inverted (shown in yellow here; left side closed, right side filled with growth medium).

c. A petri dish containing a basalt rock submerged in 50% R2A for ground experiments.

d. ESA astronaut Luca Parmitano places an experimental container in the KUBIK incubator on the International Space Station. (Image Credit: ESA)

Figure-3. ESA astronaut Luca Parmitano taking photographs of the BioRock experiment on the International Space Station. (Image Credit ESA, NASA)