Astronauts could one day end up eating asteroids

Future astronauts could eat a nutritionally perfect diet made from bacteria reared on ground-up asteroids, to produce a kind of milkshake or yogurt.

While astronauts on the International Space Station have experimented with growing salad leaves, the vast majority of food consumed in space is transported from Earth. This would become impossible for more distant, longer-lasting space missions, so Joshua Pearce at Western University in Ontario, Canada, and his colleagues decided to investigate using bacteria to convert carbon-containing compounds from asteroids into edible food.

They have yet to carry out this process using real asteroids, but Pearce and his team have performed similar experiments using bacteria to break down plastic from leftover army ration packets. To do this, they heated the plastic in the absence of oxygen, a process called pyrolysis, and then fed this to a mixture of bacteria that eat carbon.

“When you look at the pyrolysis breakdown products that we know that bacteria can eat, and then what’s in asteroids, it matches up pretty reasonably, actually,” says Pearce. “So I think this can actually work.”

The collective bacteria end up looking “something like a caramel milkshake”, says Pearce, and the team has also experimented with drying out this substance to produce something like yogurt or even a powder.

While that might not sound particularly appetising, Pearce says the bacteria are remarkably well-suited for human needs. “We did a nutritional analysis, and it turns out to be almost a perfect food,” he says. “It turns out that the bacteria consortium that we were using, more or less, has a third each for protein, carbs and fat.”

If the idea is sound, a 500-metre-wide asteroid similar to Bennu, which NASA visited in 2020, could feed between 600 and 17,000 astronauts for a year, says Pearce. The exact amount depends on how efficiently the bacteria can digest the asteroid’s carbon compounds.

A fully operational asteroid food project would require an “industrial-sized super machine” in space, he says, but the researchers hope to begin testing the idea on a smaller scale in the coming year, starting off with coal and then moving to meteorites that have fallen to Earth, which they are currently working on a proposal for. “It’s super expensive and we have to destroy [the meteorites], so the people that collect rocks were not happy when we made these proposals,” says Pearce.

“There is definitely potential there, but it is still a very futuristic and exploratory idea,” says Annemiek Waajen at Free University Amsterdam. “It is good to think about these things, but in terms of technique, there is still quite some development necessary to be able to use these methods.”

The success of the process will depend on how many of the carbon compounds inside asteroids are suitable for bacterial food, says Waajen. Based on meteorite compositions on Earth, it is likely to be somewhere in the middle of the range the team calculated, she says.