Photosynthesis, an ancient process dating back 2.3 billion years, has played a vital role in supporting life on Earth. This remarkable yet still partially understood reaction enables organisms to convert sunlight, water, and carbon dioxide into oxygen and energy in the form of sugar. While photosynthesis is often taken for granted on our planet, its rarity and value become evident as we venture beyond Earth. Recent advancements in artificial photosynthesis offer promising possibilities for space exploration and colonization, as explored in a new study published in Nature Communications.
The challenge of space travel lies in the human need for oxygen. Limited fuel capacity restricts the amount of oxygen that can be carried, particularly for long-duration journeys to destinations like the moon and Mars. Trips to Mars typically span around two years, making it impractical to transport sufficient resources from Earth. Oxygen production through carbon dioxide recycling is already accomplished on the International Space Station (ISS) using a process called electrolysis, which employs electricity from solar panels to split water into hydrogen and oxygen gases. Additionally, a separate system converts exhaled carbon dioxide into water and methane.
However, these existing technologies are unreliable, inefficient, cumbersome, and challenging to maintain. The oxygen generation process alone consumes approximately one-third of the total energy required for the ISS’s environmental control and life support system. Consequently, ongoing efforts are focused on finding alternative systems suitable for lunar missions and trips to Mars. One potential solution involves harnessing abundant solar energy in space and utilizing it directly for oxygen production and carbon dioxide recycling in a single device, much like the natural process of photosynthesis. This approach eliminates the need for complex setups where light harvesting and chemical production are separate, as seen on the ISS.
This novel approach holds significant advantages for space exploration. By capturing solar energy directly, additional thermal energy released during the process can catalyze the chemical reactions, expediting their speed. Furthermore, complex wiring and maintenance can be significantly reduced. The research team developed a theoretical framework to analyze and predict the performance of such integrated “artificial photosynthesis” devices, with a specific focus on applications in lunar and Martian environments.
Unlike plants and algae that rely on chlorophyll for light absorption, these devices employ semiconductor materials coated with simple metallic catalysts to support the desired chemical reactions. The analysis demonstrates that these devices can viably complement existing life support technologies, including the oxygen generator assembly used on the ISS. This is especially true when combined with solar concentration devices, such as large mirrors that focus incoming sunlight.
Alternative approaches are also being explored, such as producing oxygen directly from lunar soil. However, this method requires high temperatures to be effective. In contrast, artificial photosynthesis devices can operate at room temperature and at the pressures found on Mars and the moon, making them suitable for use within habitats and utilizing water as the primary resource. The presence of ice water in the lunar Shackleton crater, a potential landing site for future missions, adds to the significance of this development.
While the light intensity on Mars is weaker than on Earth due to the greater distance from the Sun, calculations show that these devices can still operate effectively on the red planet. The use of solar mirrors becomes even more crucial in this scenario. Achieving efficient and reliable oxygen production, carbon dioxide recycling, and chemical synthesis onboard spacecraft and habitats presents a monumental challenge that must be overcome for long-term space missions.
Current electrolysis systems, operating at high temperatures, demand significant energy input, and devices for converting carbon dioxide to oxygen on Mars are still in their early stages of development, regardless of whether they are based on photosynthesis or other methods. Several years of intensive research will be required before this technology can be fully utilized in space. Drawing inspiration from nature’s photosynthesis provides significant advantages and brings us closer to realizing these possibilities in the not-too-distant future.
The benefits would be substantial. Artificial photosynthesis devices could enable the creation of artificial atmospheres in space and the production of essential chemicals for long-term missions, including fertilizers, polymers, and pharmaceuticals. Moreover, the insights gained from designing and fabricating these devices could contribute to addressing the challenges of green energy on Earth.
While plants and algae currently provide us with oxygen, artificial photosynthesis devices could open up new avenues for producing hydrogen or carbon-based fuels, providing a green approach to generating energy-rich chemicals that can be stored and utilized in transportation. The exploration of space and the pursuit of a sustainable energy economy share a common long-term goal: sustainability. Artificial photosynthesis devices may prove to be a vital component in achieving this goal.
By Impact Lab