The Apollo 11 Moon landing encouraged humankind to consider and investigate life beyond Earth more than 50 years ago1. However, in contrast to its lightning-fast success in terms of the remarkable technology development of the Mercury, Gemini and Apollo programs, human space exploration has been confined in Low Earth Orbit (LEO) for the past 50 years. Nevertheless, other space agencies, such as the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), have joined the two main competitors, namely the U.S. National Aeronautics and Space Administration (NASA) and Roscosmos (the former Soviet space program). The major space agencies have mainly focused their efforts on crewed space missions in LEO (e.g., in the Space Shuttle, the Soyuz, the Salyut, International Space Station and Chinese space stations) or on uncrewed missions aimed at planetary exploration (e.g., NASA Mars 2020 Exploration and ESA ExoMars Programs). Nowadays, private space companies, such as SpaceX, Blue Origin, Virgin Galactic, are developing the next generation of spacecraft and testing a fully reusable transportation system (e.g., Starship) for crew and cargo, with the aim of sending humans into deep space in the next 5–10 years and for Mars colonization2,3,4. Even though significant progress is being made toward achieving the exploration of deep space and other planetary surfaces, more focus needs to be dedicated to how to sustain a stable settlement for a predetermined period of time on another celestial body. Indeed, two main mission scenarios have been hypothesized for the Martian exploration: a short-stay mission, which would take approximately 550 days, including the journey, and a long-stay mission with a total duration of around 900 to 1000 days5.
Expeditions to the Moon are likely to range from 20 to 30 days6,7.
The launch of NASA’s Orion vehicles, designed to support a crew of four for 21 days, will be the first crew transfer to deep space in more than 40 years. Indeed, deep space and cis-lunar orbit will be the first destination of future human journey aboard the multi-national Lunar Gateway (NASA, ESA, JAXA, and the Canadian Space Agency), which will also act as a transfer point to the Moon and Mars8. A mission onboard the Lunar Gateway is expected to last roughly 30 days, during which crew members will be exposed to a radiative environment characterized by two main sources of radiation, primarily Galactic Cosmic Radiation (GCR) and Solar Particle Events (SPE)9. In addition to the exposure to space radiation, altered gravity, isolation, and confinement, can cause systemic and physiological effects, such as increased cancer risk, muscle degeneration, bone loss, cardiovascular and circadian rhythm dysregulations, and central nervous system impairments10.
The longer missions and the farther humans will travel, the less reliant on Earth they will need to become. For example, astronauts need to carry or produce food and oxygen for long-term interplanetary travel lasting months or years11,12.
For example, ~1.8 kg of food per day would need to be sent for each crew member if we were to provide astronauts with prepared food from Earth, similar to what occurs during missions to the ISS13. A crew of six members would require a 1000-day supply of food, which would increase the initial mass of the transit vehicle by more than 108 metric tons after accounting for the additional vehicle and fuel weight required to transport the food and assuming a 10:1 vehicle-to payload ratio14. Sending necessities from Earth on long-duration missions is therefore impractical given cost projections (e.g., on the order of $300,000 per kg sent to Mars15), as well as the fact that a diet entirely of packaged foods would prove to be inadequate in the long-term due to its nutritional deficiency.
Therefore, considering a 3-year mission to Mars and a crew of 6 astronauts, a total payload of 12 metric tons would be necessary as food and water16, or17 calculated for a long-duration mission of 30 months (assuming 30-day months), that one crew member requires 2250 kg of water and 1359 kg of food (i.e. about 26 metric tons for 6 crew members during 36 months).
For these reasons, it is necessary to become less dependent from Earth, considering that the lack of cargo resupply missions and communication delays can negatively impact human health and emergencies, emphasizing the need for crew members to be self-sufficient in preventing and managing emergencies and risks18. Moreover, costs can be dramatically decreased by recycling, using bioregenerative systems, using materials of lower mass, or using materials found at the destination, known as ‘In Situ Resource Utilization (ISRU)’19. Synthetic biology has great potential to contribute crucially to these solutions for space exploration. Space synthetic biology, which straddles the lines of aerospace engineering and bioengineering, is a highly interesting field for long-duration space missions. For example, synthetic biology approaches may convert both astronaut waste resources and in situ destination planet resources into useful products while consisting of less mass (savings as much as 26–85% depending on the application) than conventional abiotic means20. For example, by naturally utilizing solar energy and only growing when activated using the available nutrients at the destination, biological technology can help reduce power demand and launch volume, two additional crucial space parameters.
Given the increasing importance of synthetic biology to support future deep space missions, in 2020, ESA brought together leading experts in the fields to define the main topics, carefully reviewed the scientific literature, with the goal of advancing the scientific community’s knowledge in the field of space synthetic biology.
Figure 1 describes the main themes and key areas that have been recognized and agreed upon. They are divided into (A) In situ Resource Utilization for Human Outposts on Mars and Moon, (B) Bioregenerative Life Support and Food production, (C) Radiation and Stress Protection and (D) Human Health. Each key topic is described in more detail in the following sections.
Fig. 1: Key space synthetic biology topics. As identified in the 2023 ESA SciSpace Science Community WhitePaper, key space synthetic biology topics, are (A) In situ resource utilization for human outpost on Mars and Moon, (B) Bio-regenerative life support and foodproduction, (C) Radiation and stress protection and (D) Human healt. Full size image
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