Plants have been grown in soil from the moon for the first time.
The milestone in lunar and space exploration is a first step towards one day growing plants for food and oxygen on the moon or during space missions.
In the new study University of Florida researchers showed the arabidopsis plant - thale cress - can successfully sprout and grow in soil that was collected from the Apollo 11, 12 and 17 missions.
Their study also investigated how plants respond biologically to the moon's soil, also known as lunar regolith, which is radically different from soil found on Earth.
The research comes as the Artemis Program plans to return humans to the moon.
Rob Ferl, one of the study's authors and a professor of horticultural sciences in the UF Institute of Food and Agricultural Sciences (UF/IFAS), said: "Showing that plants will grow in lunar soil is actually a huge step in that direction of being able to establish ourselves in lunar colonies."
He added that it was also important to show that lunar soils were not harmful to terrestrial life, and also that terrestrial life could establish itself.
But what do the findings mean in relation to growing food fit for human consumption on the moon?
Anna-Lisa Paul, one of the study's authors and a research professor of horticultural sciences in UF/IFAS, explained: "So the plants that were responding the most strongly to what we would call oxidative stress responses, those are the ones especially in the Apollo 11 samples, they are the ones that turned purple.
"And that's the same thing that's in blueberries and cranberries, and all of those, those dark red and purple fruits that are healthy for humans because of their anti-oxidative properties.
"We definitely don't know the nutritive value of these plants, but it is likely not to pose any threat to humans - it's hard to say, but it's more likely that the chemicals that plants produce in response to stresses are ones that also help human stresses as well.
"So it's likely to be a more benign or helpful response than the other way around."
Crops are 'not tasty'
Dr Paul added that while arabidopsis is edible, it is not tasty.
It belongs to the same family as mustard, cauliflower and broccoli, so many of the things learned could translate into the same kind of metabolic strategies and processes "that our good friend broccoli uses", Dr Paul said.
The researchers set about planting seeds in lunar soil, adding water, nutrients and light, and analysing the growth and results.
But because of the rare nature of the samples, the scientists had just 12 grams - just under three teaspoons - of soil from the moon to work with.
On loan from Nasa, they had applied three times over the course of 11 years for a chance to work with the soil.
And 18 months ago, they were given the samples.
Before then, the samples had been kept in pristine condition so other analysis could be carried out, and releasing them for plant growth experiments would have seen them become unsuitable for other research.
The upcoming Artemis mission will require a better understanding of how to grow plants in space, and so the experiment became more immediately relevant.
The researchers used thimble-sized wells in plastic plates normally used to culture cells, and once each was filled with roughly one gram of lunar soil, it was moistened with a nutrient solution and added a few seeds from the arabidopsis plant.
The plant is well documented in scientific research and its genetic code has been fully mapped.
In order to conduct comparisons, seeds were also planted in soil from Earth that mimics real lunar soil, as well as simulated Martian soils and terrestrial soils from extreme environments.
The researchers were surprised to see that all of the seeds planted in the lunar soils sprouted.
However, just because the plants all grew, this does not mean they did so as normal.
Some of those grown in the lunar soils were smaller, were different colours, grew more slowly or were more varied in size than their counterparts.
These were all physical signs that the plants were working to cope with the chemical and structural make-up of the moon's soil, which has lots of tiny glass fragments containing gases and even metallic irons.
According to the scientists, how plants respond to lunar soil may be linked to where the soil was collected.
For instance, the researchers found that the plants with the most signs of stress were those grown in what lunar geologists call mature lunar soil.
Dr Ferl said: "It's really good news that plants can grow in the lunar soils.
"This presents to lunar colonists, to lunar scientists, a bunch more options than if they simply failed to grow there.
"But the bottom line is that until it was actually done, nobody knew whether plants, especially plant roots, would be able to interact with the very sharp antagonistic soils the lunar regolith presents."