Is space lettuce good for you?

10 March 2020

LETTUCE

lettuce crop in the soil

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Lettuce grown on the International Space Station (ISS) has similar nutritional and bacterial content to that grown on Earth, researchers have found this week.

For the first time, scientists were able to compare lettuce harvested on the ISS to that harvested on Earth.

“The nutritional composition was very similar, within an experiment. The microbial content was increased on the space station [lettuces], but the plants were safe for the astronauts to eat,” says Gioia Massa, one of the study’s authors from the Kennedy Space Center.

The additional microbes found on the space-grown lettuce were not much of a surprise, since the growing conditions on the ISS can’t be as tightly controlled as those on Earth.

“Plants that were grown on the space station are essentially being grown in a house, where there are six people living, working and exercising every day,” explains Massa. “There tends to be a higher level of microorganisms in that environment.”

The earth-based growth chamber used data on the temperature, humidity and carbon dioxide levels sent back from the space station to mimic the conditions experienced by the space lettuce.

Despite these conditions, the similarity of the nutritional content in the lettuces was a surprise for the researchers.

Plants on the space station experience a lot more variation in water availability than those on Earth because of the low gravity. “It’s really difficult to water plants in space,” Massa points out. “On Earth, excess water just drains away, whereas in space it builds up around the plant roots.”

Understanding the bacterial and fungal population that naturally arises on the lettuces may be the first step in trying to control that microbiome to encourage future growth.

“A microbiome could be designed for the space environment,” Massa suggests, “to help provide a stable, beneficial ecosystem that can outcompete any human or plant pathogens.” But, it’s very early days, Massa warns.

In the meantime, it sounds like the astronauts could soon be looking forward to their very own home-grown space salad.

“We are building on this by testing other leafy green crops in space.” says Massa. “Hopefully we can add things like small fruits - peppers and tomatoes - in the next couple of years to the space diet.”

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