But for a longer, more distant mission to Mars, which might last three years, that would not be possible. Indeed, food and other supplies might be sent ahead of time, meaning the meals might be sitting around for five years before the astronauts eat them.

“It’s going to be old by the end of that mission,” said Grace L. Douglas, lead scientist for advanced food technology at NASA’s Johnson Space Center in Houston.

By that time, some of the nutrients and taste will most likely have decayed. And if astronauts do not enjoy what they are eating, they may eat less, potentially setting off a cascade of negative health consequences including loss of weight and muscle and damage to the cardiovascular system.

“We don’t have a system that will meet the requirements currently,” Dr. Douglas said.

The space agency is trying to develop processed foods that last longer, as well as methods for efficiently growing crops in a weightless environment. If that requires too much work, it would not be an effective use of an astronaut’s time.

“You want them out exploring,” Dr. Douglas said, “and not worrying about their next meal.”

Enter Veggie, a plant growth chamber aboard the International Space Station since 2014. Dr. Massa’s paper analyzes lettuce experiments from 2014 to 2016. (The space station astronauts did not wait for the final scientific analysis for safety assurances. In 2015, they ate part of their harvest.)