Can Asteroids Serve as a Food Source for Astronauts?

By Sam Fan 樊潤璋

Can We Eat Rocks?

Imagine you’re an astronaut, floating in the cold, infinite void of space. The isolation is overwhelming, the stars are your only company, and every pre-packaged meal reminds you of the tether that ties you to Earth. Bid a farewell to the crusty steak and crunchy toast — nothing is worse than life without the delicious Maillard reaction. Yet, an even more daunting scenario could be the future of dining for astronauts as we explore the possibility of turning asteroid material into sustenance. None of the people on Earth would ever think to ask, "Can we eat rocks or dirt?" — unless you are running out of money. However, always relying on Earth-dependent resupply missions is impractical for prolonged journeys to deep space.

Innovative approaches, such as bioregenerative systems that grow plants, algae, mushrooms, or even cultured meat onboard spacecraft, could be promising. However, these systems require a significant amount of resources, including water, light, and nutrients [1, 2]. In comparison, applying the mining concept to food is tantalizing. Could the vast resources of space itself provide sustenance? Scientists are now exploring the possibility of mining asteroids to create food. The carbon-rich asteroids may hold the key, offering a potential source of organic materials that could one day be converted into food for astronauts [2].

The Science Behind Asteroid Food

These carbon-rich asteroids, including the famous Murchison meteorite that crash-landed in Australia in 1969, contain organic substances in various forms, such as aliphatic hydrocarbons and insoluble organic matter (IOM) [2]. The food mining process involves feeding relatively short hydrocarbons to bacteria, ideally with carbon lengths from 10 to 40 [2]. Previous studies have identified bacteria that can convert the thermal breakdown products of high-density polyethylene plastic to human edible biomass [3]. Given the similarity in composition between the breakdown products of the plastic and the asteroid material, the microbial consortium is expected to work like a team of microscopic chefs, converting raw asteroid material into food rich in carbohydrates, proteins, and other nutrients humans need to survive [2–4].

Let’s Do Some Math!

In the following calculation, asteroid Bennu is chosen to illustrate how much food an asteroid can offer [2]. Bennu is a small, near-earth carbon-rich asteroid with a mass of 7.329 × 10¹³ g. It was also the target of NASA's first asteroid sample collection mission [5]. A few assumptions are made for the calculation: First, the proportion of organic substances is based on data from the more extensively studied Murchison meteorite. Second, the maximum amount of food is calculated by considering the total amount of insoluble organic matter (IOM) in the asteroid, assuming that they can be extracted and converted into edible biomass.

Let’s first find out the mass of IOM in Bennu:

      Mass of Bennu × Proportion of IOM

      = 7.329 × 10¹³ × 0.096

      = 7.036 × 10¹² g

The extraction and conversion processes are expected to be somewhat inefficient. Assume the proportion of mass extractable for food production e is 0.32 [3], the conversion efficiency by the bacteria consortium k₁ is 0.2 [3], and the extraction efficiency of carbon material from Bennu k₂ is 0.008 [6]. The estimated mass of edible biomass offered by Bennu is:

      Mass of IOM in Bennu × e × k₁ × k₂

      = 7.036 x 10¹² × 0.32 × 0.2 × 0.008

      = 3.602 × 10⁹ g

Given that every 100 grams of edible biomass contains a total of 442 Calories, the estimated total Calories offered by Bennu is:

      Mass of edible biomass ÷ 100 × 442

      = 3.602 × 10⁹ ÷ 100 × 442

      = 1.592 × 10¹⁰ Calories

A NASA’s standard diet provides 2,500 Calories for one astronaut per day. How many years can Bennu support the need of one astronaut?

      Calories offered by Bennu ÷ 2,500 ÷ 365

      = 1.592 × 10¹⁰ ÷ 2,500 ÷ 365

      = 17,447 years

So, the result is around 17,447 years for one astronaut (or 17,447 astronauts for one year). We’re talking about an asteroid with a volume of around 62.3 million cubic meters — equivalent to about 25,000 Olympic-size swimming pools [7, 8]. To sustain just one astronaut, the daily volume of material required would be roughly the size of a quarter of a 19-seater minibus in Hong Kong [9].

A Long Way to Go

A sheer volume of asteroid material would need to be processed daily to sustain even a single astronaut. Handling such a volume in space, where every kilogram of equipment and material must be carefully managed, presents enormous logistical hurdles. For a whole crew of astronauts, demanding storage and processing capacities are almost unfeasible with current technology. So to this day, even if asteroid-based food production is an exciting concept, it is still in its infancy.

Future advancements must focus on improving the efficiency of extraction and conversion processes, reducing the asteroid material required, and developing compact, energy-efficient systems that can operate in the unique environment of space [2]. The food will also need to undergo toxicology analysis, animal studies and finally human trials to ensure safety [2]. Only then can this vision become a practical solution for long-term space exploration.

A Whole New Horizon

While the technology is still theoretical and faces significant challenges, its potential to revolutionize space travel is undeniable. This approach could reduce reliance on Earth’s resources, enabling longer missions to explore the cosmos. Though far from reality, the idea reminds us of humanity’s ingenuity and determination to adapt and thrive, even in the vast, inhospitable reaches of space.

References

[1] Douglas GL, Wheeler RM, Fritsche RF. Sustaining Astronauts: Resource Limitations, Technology Needs, and Parallels between Spaceflight Food Systems and those on Earth. Sustainability. 2021;13(16):9424. doi:10.3390/su13169424

[2] Pilles E, Nicklin RI, Pearce JM. How we can mine asteroids for space food. Int J Astrobiol. 2024;23. doi:10.1017/s1473550424000119

[3] Byrne E, Schaerer LG, Kulas DG, et al. Pyrolysis-Aided microbial biodegradation of High-Density polyethylene plastic by environmental inocula enrichment cultures. ACS Sustain Chem Eng. 2022;10(6):2022-2033. doi:10.1021/acssuschemeng.1c05318

[4] Wilkins A. Astronauts could one day end up eating asteroids. New Sci. Published online October 4, 2024. https://www.newscientist.com/article/2450719-astronauts-could-one-day-end-up-eating-asteroids/

[5] Barnett A. Bennu. NASA Science. Updated December 17, 2024. Accessed January 22, 2025. https://science.nasa.gov/solar-system/asteroids/101955-bennu/

[6] Zhang L, Dong H, Liu Y, et al. Bioleaching of rare earth elements from bastnaesite-bearing rock by actinobacteria. Chem Geol. 2018;483:544-557. doi:10.1016/j.chemgeo.2018.03.023

[7] Lauretta DS, Bartels AE, Barucci MA, et al. The OSIRIS‐REx target asteroid (101955) Bennu: Constraints on its physical, geological, and dynamical nature from astronomical observations. Meteorit Planet Sci. 2014;50(4):834-849. doi:10.1111/maps.12353

[8] Bureau of Meteorology, Australian Government. When dam size matters. Updated October 25, 2012. Accessed January 22, 2025. https://media.bom.gov.au/social/blog/39/when-dam-size-matters/

[9] Toyota Hong Kong. Toyota Coaster. Accessed January 22, 2025. https://www.toyota.com.hk/en/our-vehicles/coaster/