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Plants grown in lunar soil for the first time
Plants have been shown to grow in lunar soil for the first time, opening up the possibility of growing food on the Moon.
However, the plants' growth was negatively affected by the soil, meaning there is still some way to go until farming on the Moon becomes a viable prospect.
They may be a few small plants, but they could represent the beginning of a giant leap for human space exploration.
A team of scientists from the University of Florida showed that thale cress, a member of the mustard family, could germinate from a seed and grow in soil samples taken by Apollo 11, 12 and 17.
Co-author Prof Robert Ferl says, 'When humans move as civilisations, we always take our agriculture with us. This will be incredibly important on the Moon.
'The ability to take plants successfully is how we'll grow our own food, purify our air and clean our water; things that will allow us to stay there for a while. We can grow plants hydroponically, but the idea of bringing lunar soil into a lunar greenhouse is the stuff of lunar exploration dreams.
'Showing that plants will grow in lunar soil is a huge step in being able to establish lunar colonies.'
However, before astronauts start making their own egg and cress sandwiches, more research will be needed to discover why the growth of the cress plants was stunted by the Moon's regolith.
Dr Sandra Knapp, a Merit Researcher in botany at the Museum who was not involved in the study, says, 'Toxic soils can cause growth defects in plants, or kill them through toxicity.
'However, many plants are very capable of adapting to toxic conditions. Some plants are capable of adapting to mine tailings, which are high in heavy metals, but not all of them.
'While there is no oxygen or carbon dioxide in the atmosphere for plants to grow on the surface of the Moon, plants could theoretically alter lunar soil in the same way they alter soil here on Earth over time if they were grown in the conditions of our planet.'
The findings of the study were published in Communications Biology.
Plants have been grown in space by astronauts and cosmonauts for over 40 years. Image © NASA/JSC
Have plants been grown in space before?
Outer space is a harsh environment for life. The lack of food, oxygen or water are just some of the problems astronauts face.
Many of these problems, however, won't require technology to overcome, but instead the ability to grow plants. Plants can convert waste carbon dioxide breathed out by astronauts into oxygen, while their nutritional properties can ward off hunger and diseases such as scurvy.
This has made research into growing plants in space a priority for decades. In 1966, the Soviet Union launched seeds into orbit which were successfully grown following their return to Earth.
Subsequent missions have seen humans grow plants in space. Thale cress was the first plant to be grown in space in 1982, while Russian cosmonauts have been eating some space-grown plants since the early 2000s and NASA astronauts ate their first space crop in 2015.
In 2019, the first probe to land on the dark side of the Moon, China's Chang'e-4, took seeds with it in a biosphere experiment. Cotton seeds successfully sprouted, the first to do so on another world, but were killed the following day after temperature control of the experiment was lost.
However, until now plants had never been grown in lunar soil, known technically as regolith. The recent study sought to change that.
Lunar soil from the Apollo 17 mission, which accumulated on a component of the lunar rover, was used to grow some of the thale cress. Image © NASA/JSC
How well did plants grow in lunar soil?
The researchers planted thale cress seeds in soil from one of three separate Apollo missions, which were collected from different areas of the Moon, as well as a lunar soil simulant being used as a control. A nutrient rich solution was used to keep the growth plates moist and feed the plants.
Thale cress sprouted and grew in all three lunar soils and the control but grew most strongly in the simulated lunar soil. Plants grown in lunar soil were generally smaller, took longer to develop, and showed signs of stress such as stunted growth and colour changes.
Co-author Prof Stephen Elardo explains, 'The primary reason that plants grown in lunar regolith presented such stress-related responses is that Apollo regolith is quite different from terrestrial substrates in which plants normally grow.
'The Moon is very poor in water, carbon, nitrogen and phosphorus, so naturally lunar soils don't have the nutrients to support plant growth.
'The physical characteristics are also not terribly hospitable. Lunar regolith is very fine grained, but the fragments are quite sharp and abrasive. It is not a benign substrate.
'Additionally, there are lots of tiny glass fragments and iron fragments that we don't tend to find in Earth's soils, which plants have not evolved to grow successfully in.'
Analysis of the plants' genetics showed that genes associated with nutrient metabolism and metal stress were strongly activated in all of the lunar soils, but that the exact genes changed depending on which soil the cress was grown in.
Plants grown in soil from Apollo 11, where samples were collected from the Moon's Sea of Tranquillity, grew less well than plants grown in soil from Apollo 12 and 17, where samples came from the Ocean of Storms and the Taurus-Litrow Valley respectively.
The differences are believed to relate to the age of the different soils, and how their composition has been changed by exposure to space. This could help inform where to set up future lunar bases.
Lead author Dr Anna-Lisa Paul says, 'Soils from more mature sites that have been exposed to cosmic wind for longer were more toxic to the plants, and one thing we could do to mitigate this in future is by choosing our sites more carefully.
'We can then choose where to mine materials to use as a substrate.'
The scientists hope to further investigate how the properties of lunar soil are affecting plant growth, and how it could be processed to improve its use in growing the future food and oxygen converters of astronauts.
