Artificial photosynthesis could help astronauts breathe on Mars

"This work seeks to establish the theoretical foundations of PEC devices on the Moon and Mars and delivers the first foray into utilizing them for oxygen production and carbon dioxide recycling."
Amal Jos Chacko
Representational image of Mars
Representational image of Mars


“But how will we breathe?” has been a question in every person’s mind when thinking about space exploration.

The need to save space and fuel put a limit on the amount of oxygen astronauts can carry with them and the vastness of space and flight times of two years for a one-way trip to Mars rules out frequent replenishing of oxygen and other supplies.

Most of the oxygen on the International Space Station (ISS) is obtained through electrolysis— a chemical process that leverages electricity to split water into hydrogen and oxygen. A separate system converts the carbon dioxide exhaled into water and methane.

However, this method hogs 1.5kW out of the 4.6kW energy budget, about a third of the total energy required to run ISS’s Environmental Control and Life Support System (ECLSS) responsible for providing clean water and air to the crew and laboratory animals.

Light to the rescue

A study published in the scientific journal Nature Communications assesses the viability of replacing existing oxygen and fuel production systems with photoelectrochemical (PEC) devices.

This process is akin to photosynthesis in plants and takes water as input and involves the separation of light harvesting and chemical production. Not only would it drastically diminish the weight and volume of the system, but it would also provide significant gains in terms of efficiency.

Whereas plants rely on chlorophyll to absorb light, the proposed device would instead utilize semiconductor materials coated with metallic catalysts that support the desired chemical reaction.

Furthermore, the study establishes a framework capable of predicting the performance of these PEC devices on the Moon and Mars.

In an article in The Conversation, Katharina Brinkert, Assistant Professor in Catalysis at the University of Warwick, United Kingdom, and lead researcher of the study, affirmed that these photoelectrochemical devices could be augmented with current life support technologies, such as ISS’s oxygen generator assembly.

The ability to operate at room temperature edges these artificial photosynthesis devices over alternate methods such as generating oxygen from regolith, a feat experimented with by NASA scientists involving the use of high temperatures.

However, not all factors are in favor of the PEC approach. Mars, being further away from the Sun than the Earth, receives lesser light, a resource central to photoelectrochemical reactions.

The study underlines the importance of solar mirrors to combat this reduction in light intensity. 

Taking a leaf out of Nature’s book.

Our space exploration dreams hinge on our ability to develop green technologies such as the PEC device which could help create artificial atmospheres in space as well as attain our energy economy goals on Earth.

Although the study demonstrates the viability of PEC devices, their efficiency in microgravity, and theoretical scalability, it remains to be seen how well they translate to practice.

Further research could see Artificial Photosynthesis become a key cog in our quest to produce easy-to-store and easy-to-transport energy-rich chemicals.

Study Abstract

Human deep space exploration is presented with multiple challenges, such as the reliable, efficient and sustainable operation of life support systems. The production and recycling of oxygen, carbon dioxide (CO2) and fuels are hereby key, as a resource resupply will not be possible. Photoelectrochemical (PEC) devices are investigated for the light-assisted production of hydrogen and carbon-based fuels from CO2 within the green energy transition on Earth. Their monolithic design and the sole reliance on solar energy makes them attractive for applications in space. Here, we establish the framework to evaluate PEC device performances on Moon and Mars. We present a refined Martian solar irradiance spectrum and establish the thermodynamic and realistic efficiency limits of solar-driven lunar water-splitting and Martian carbon dioxide reduction (CO2R) devices. Finally, we discuss the technological viability of PEC devices in space by assessing the performance combined with solar concentrator devices and explore their fabrication via in-situ resource utilization.

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