Growing plants in space has an obvious health benefit for astronauts: it means they can stay fed with fresh fruits, grains and vegetables. But there are more health concerns in space than just having enough to eat.
Outer space is not an environment designed for the human body, and astronauts can spend lengthy periods of time there. The nearest pharmacies are on Earth, hundreds of miles away. It’s important to stock up on any medicines that might be needed.
Of course, unless your medicine stocks are resupplied, they’ll eventually run out. Even if your supplies are vast, they won’t necessarily last; drugs have been found to decline in effectiveness more quickly in space than on Earth. If we could grow essential medicines in space, though, astronauts could remain supplied indefinitely.
This is a topic that’s been in the news recently due to research into one of the big obstacles to long space flights: bone loss in astronauts.
Bone loss in space
Aboard the International Space Station (ISS), astronauts exercise for about two hours per day to fight against the health problems caused by low gravity. One of these problems is osteopenia: the loss of bone density.
Without the pressure that gravity exerts on your bones, your body has less incentive to reinforce them. Astronauts have been observed to lose about 1 to 2% of their bone density per month on the ISS: a rate of loss about ten times higher than osteoporosis. In other words, in a month, astronauts lose almost as much bone mass as an osteoporosis patient would in a year.
When astronauts come back to Earth with their bones weakened, they’re in danger of breaking them. ESA has written about how dramatic bone loss in astronauts can be:
In microgravity weight-bearing bones are particularly affected and bone mass decreases of up to 20% have been reported after a six month mission. The astronauts returning from long duration space-flights are at risk of fracture and are consequently subject of specific attention and care.
Most missions to the ISS are about six months long, and you can get to the moon and back in about a week. If we start travelling further afield, though, astronauts will need to be able to endure space for longer periods.
It took the NASA rover Perseverance about six and a half months to reach Mars after its launch in 2020. If a manned craft took the same amount of time, it would take over a year just to get to Mars and back. It’s unlikely that we’d send a mission to Mars just to glance at it and return, though; the crew would probably spend several months in orbit around Mars, making observations and performing experiments.
Let’s estimate that a spaceship’s crew might spend about a year and a half in space on a mission to Mars, then: thirteen months travelling and five months at Mars itself. Even this conservative estimate is three times longer than the average ISS mission, and we already know that bone mass decreases of up to 20% have been seen after just six months in space. How do we prevent dangerous levels of bone loss on these longer missions?
Space lettuce for bone density
Researchers at the University of California, Davis have been trying to tackle this problem. They’ve developed lettuce containing PTH, a hormone that stimulates bone growth, in the hope that simply eating this lettuce will help to counteract the bone loss caused by low-gravity environments.
If this lettuce proves helpful to astronauts, it may well be possible to grow it in space; after all, other varieties of lettuce have already been grown on the ISS. Indeed, the fact that lettuce had already been grown in space was part of the reason the researchers chose to modify lettuce specifically.
There’s more research to be done before astronauts start eating medically prescribed salad. For example, the researchers want to make sure that the lettuce is ready for human consumption, and that it maintains its PTH levels from generation to generation. But it’s a fascinating project, with the potential to address a real obstacle to long space flights, and it could potentially also help to stave off osteoporosis here on Earth.
If you’d like to know more, Karen McDonald and Kevin Yates, two of the researchers who helped to develop this lettuce, have spoken about the project in this video from the American Chemical Society.
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For more about growing plants in space, return to our AstroPlant page.
