It’s hard to imagine anyone being more excited about eating lettuce than the three astronauts aboard the International Space Station (ISS) were yesterday, when they tucked into the first leaves of space-grown lettuce they’ve been allowed to eat. Despite having to sanitise the leaves first, with citric-acid-based, food-safe, antibacterial wipes (yummy!), they broke out the oil and vinegar and tucked in with gusto. They even thanked Mission Control and the scientists for giving them the opportunity to take part in this payload mission, and saved some samples for the Russian cosmonauts who were outside on a spacewalk at harvest time.
The astronauts proclaimed their simple space salad “Awesome!”, and said it tasted like arugula (that’s US English for rocket). The variety chosen, a red romaine called ‘Outredgeous’, could become increasingly popular on Earth after its 15 minutes of space fame. Readily available in North America, seeds are harder to come by in the UK, but are included in the Wildfire Lettuce Mixture sold by Nicky’s Nursery.
It’s over a year since I blogged about astronaut Steve Swanson gardening on the ISS. Although he harvested his crop, he wasn’t allowed to eat it. The leaves had to be frozen and returned to Earth for safety tests first.
And whilst space veggies may capture the imagination, and be a way to encourage kids to eat their ‘reds’, the astronauts won’t be growing much of their own food any time soon. Although we’ll need sustainable systems for the planned long duration missions to Mars, scientists are still figuring out how to build them.
In the meantime, we can be amazed at this achievement, and the benefits it is bringing to agriculture at less rarefied atmospheres. NASA have an article on the benefits of space farming, which include improvements to commercial LED lighting systems, and ethylene-scrubbers that also remove airborne bacteria, moulds and fungi, mycotoxins, viruses, and odours and can be used in distribution facilities, food processing plants, wineries, distilleries, restaurants, and large floral shops and have also been added to fridges. They can aid in food preservation and disease control, and sensors developed to monitor the crop whilst the astronauts are busy elsewhere are already helping Earthlings look after their houseplants!
I’m not a chemist, but I do find plant chemistry (and the links and patterns between different plants) to be a fascinating topic. Fortunately there are chemists out there who can bring these to our attention, and Compound Interest includes some great plant-related infographics amongst a wider spread of chemical topics.
If you click the infographic below you’ll be taken to the site, where you can find a larger version, and the informative post that goes with it. Suffice to say I didn’t know that the cultivation of blackcurrants (Ribes nigrum) was (and in some places, still is) banned in the US due to disease worries. They’re a very popular fruit crop in the UK, in gardens and allotments. I’m pleased to say that my little specimen, which I bought in a pound shop in the spring, is doing quite nicely (although it would like to get out of a pot and into a permanent home).
Compound Interest talks about the anthocyanins that give blackcurrants their colour, and the fact that the berries can have far higher levels of vitamin C than an orange.
And then it says that some people find the smell of the berries reminds them of cat pee. Now, this isn’t a problem I have myself but apparently there is a chemical link between the two – in the form of a sulfur compound called the ‘cat ketone’.
Resurrection plants can survive extreme dehydration, even over months or years. In scientific terms, they are called poikilohydric. This one, the Rose of Jericho (Anastatica hierochuntica), is native to the deserts of North Africa.
Not a plant you’re likely to find in a garden, but you may unleash a horde of zombie plants without realising it!
Astronaut Steven Swanson tending to the Veggie garden on the International Space Station. Image credit: NASA
The aim of my GlutBusters project is essentially to change the way we choose the crops we grow in our kitchen gardens, moving the focus away from the ‘maximum yield’ mentality that can bring problematic gluts and ‘hungry gaps’ and towards planning for diversity rather than sheer quantity. It’s an idea that relies on a modern reality – access to crops grown on farms and commercial suppliers means that gardeners with a lack of time and/or space don’t need to aim for self-sufficiency.
But what about gardeners in space? How would they choose which crops to grow? Currently astronauts are supplied from Earth, and it’s not something they need to worry about. But it costs getting on for £14,000 to launch every kilo into space (it depends a little bit on which launch system is used), so giving astronauts the means to grow some of their own food could prove cost-effective. That’s particularly true for long duration missions, such as a manned mission to Mars, or a lunar base. The more self-sufficient we can make the crew, the less they will need to be resupplied from Earth. However – it’s not only food they need. Plants could form a part of their life support system, removing carbon dioxide and producing oxygen, as well as recycling waste products and cleaning up waste water.
In the early 1960s, NASA began to look into the science and technology of Controlled Ecological Support Systems (CELSS), which could do all of those things. It was Boeing Company that produced the first list of suggested plants, which included 14 different crops: lettuce, Chinese cabbage, cabbage, cauliflower, kale, turnip, Swiss chard, endive, dandelion, radish, New Zealand spinach, tampala (amaranth), and sweet potato.
Crops tested in VEGGIE plant pillows include lettuce, Swiss chard, radishes, Chinese cabbage and peas. Image credit: NASA
There’s a lot of leafy vegetables in that list, and that’s in part due to the criteria by which they were selected. The idea was to have plants that have compact growth, so they don’t take up too much space. They need to be productive (usually ‘early’ varieties, that achieve a harvestable size quickly), and easy-to-grow. The crew don’t have much spare time to be tending veggies, nor do they have time for food processing, or space for complex machinery to do things like threshing or milling. Ideally the crops want to produce as little inedible biomass as possible, although some later versions of CELSS incorporate insects or animals that can process inedible crop wastes into edible protein.
Space veggies have to be able to cope with less-than-ideal conditions, including low light levels and problems with the water supply. The latter would be less of an issue on the Moon or Mars, where there is some gravity to ensure that irrigation water does what we need it to do and doesn’t constantly try to float off and short-circuit expensive computer equipment!
There also has to be a focus on nutritional balance, as a complete diet would be needed to keep astronauts healthy in the long term, whether all nutrients are being supplied by the CELSS, or some come from Earth-supplied rations. Home-grown food also helps to relive ‘ration fatigue’ for astronauts – fresh fruit and veg are the most eagerly awaited part of every supply run to the International Space Station. And there are psychological benefits to gardening as well, with astronauts reporting positive effects from tending plants in space.
The list of plants included in a CELSS also depends on the culture of the scientists building it, and that of the astronauts it will feed. NASA is planning on sending along lettuce, spinach, carrots, tomatoes, green onions, radishes, bell peppers, strawberries, fresh herbs and cabbages with their mission to Mars; Chinese scientists would rather go with rice, soy beans, sweet potatoes, a variety of ‘green-yellow vegetable’ (e.g. komatsuna), stem lettuce and even mulberry trees (to feed silkworms, to produce edible pupae).
And plant breeding can overcome issues with some species – a special dwarf variety of wheat (‘Apogee’, on which seed heads develop after just 23 days) was developed to be grown in space – although the technology necessary to grow plants successfully in zero gravity is still being developed.
In 2007, garden designer Sarah Eberle won a gold medal at the Chelsea Flower Show for her interpretation of a garden that could be grown in a protected habitat in Mars. She visited Sicily to choose plant varieties that she thought might thrive in the Martian environment and that had multiple benefits, including their colour, nutrition and medicinal effects. She included coffee, wheat and calendula, with carob as a chocolate substitute. Another area of the garden was set aside for ‘luxury’ crops such as pistachios and olives, along with plants with healing properties such as arnica and the Opium poppy. If I end up going to Mars I’d like to sign up to go along with Sarah’s garden, please!
So… if you found yourself on a deserted planet, with the right kit for growing a space garden, what would you choose to grow? Let me know your thoughts in the comments!
Astronaut James B. Irwin scoops up lunar soil during Apollo 15, 2nd August 1971.
When Neil Armstrong made his giant leap for humankind in 45 years ago, he got covered in Moon dust. Throughout the Apollo missions, dust was an issue. Fine but rough, it caused problems with the space suits, and created mini dust storms in the cabin once the landers launched back into space.
On Earth, mineral soils are formed from the underlying rock by weathering, which is a collection of natural processes that gradually break down the rock. Weathering can be mechanical (through atmospheric conditions such as heat, water, ice and pressure) or chemical (when the surface rock reacts with water, oxygen or chemicals produced by plants). The rock particles then combine with organic matter to form what we know as soil.
On the Moon, that doesn’t happen. Lunar dust is formed from lunar rock (regolith) when small meteorites hit the Moon’s surface and pulverize the rock. Some of the rock melts and then cools, coating the dust with a glassy shell. There’s no organic matter for the dust to combine with. UV rays by day, and solar winds by night, create charged particles and give lunar dust ‘static cling’. Oh, and tiny specks of iron make it magnetic. So it’s not your run-of-the-mill Earth soil.
But would anything grow in it? The short answer is no – the minerals it contains are locked up in a form that plants can’t access. Whilst it might be possible to use Moon rock as a ‘substrate’ for hydroponic growing (essentially there merely to hold the plants up), all of their nutrients would have to be supplied with a fertilizer.
But that’s not the final word on the subject. NASA did some plant experiments with Moon rock at the time of the Apollo missions (mainly as part of their quarantine procedures to make sure they hadn’t imported health risks with their souvenirs). They didn’t attempt to grow plants in lunar soil, but they exposed plants to it. Not only did they find no negative effects, the experiments seemed to show that the plants benefited from the Moon dirt – results that have not been replicated. Since then the Moon samples have been considered a precious commodity and have not been made available for destructive research such as grinding them up to grow plants. So researchers have to use ‘simulants’ – Earth rocks that are similar in type to those found on the Moon.
Early in the new millennium, a team of researchers led by Natasha Kozyrovska and Iryna Zaetz from the National Academy of Sciences in Kiev, conducted a series of experiments with French marigolds (Tagetes patula) in one such simulant – anorthosite. They published their results in 2006.
Unsurprisingly, seeds sown in plain old crushed anorthosite didn’t grow into plants. But they were the control group. A second set of seeds was inoculated with a microbiome (bacteria and fungi known to promote healthy growth), whilst the crushed rock was also seeded with bacteria – and in this more complex ecosystem the seeds were able to germinate and grow into flowering plants. The microorganisms present were helping the plants to extract nutrients from the rock, and the authors suggested that this might be a way of starting to grow plants on the Moon.
Reading through the paper, I got the impression that what the authors were proposing was a kind of space permaculture. Lunar regolith is sterile, which not only means that plants can’t rely on microorganisms to release nutrients, but also means that any soil made from them would be a blank canvas for microbes accidentally brought from Earth. Rather than fungi and bacteria that promote healthy growth, you could end up with an imbalance – an environment that is harmful to plant growth. The idea of inoculating the seeds and the regolith was to promote a healthy soil environment that could protect plants against pests and diseases.
The selection of French marigolds was not random. The scientists wanted to grow ‘pioneer’ plants that would not to be too fussy to grow in the nutrient-deprived lunar soil. These ‘first generation’ plants would then be composted to create organic matter and real soil, but the goal was also for them to be multipurpose. They were looking for plants to recycle waste products and produce oxygen, which had potential nutritional and medicinal benefits, and that flowered and so could improve the psychological well-being of the astronauts. Providing all these benefits, whilst kick-starting a sustainable ecosystem that makes use of local resources, is a tall order – but apparently French marigolds fit the bill!
The paper mentions another problem with growing plants on the Moon – the Sun is up for about two weeks, and then down again for the same period of time. If you don’t want to go to the expense of supplementary lighting, it reasons, the only solution is to chill your plants so that they are dormant until the Sun comes out again. In the meantime, I guess those long nights are perfect for forcing vegetables and sprouting seeds! Or perhaps mushroom cultivation….
And so it’s time, once again, for you to choose the next leg of our space blog adventure! Would you like to know more about growing fungi in space, how scientists choose which crop plants will be grown in space, or the Moon trees (grown from seeds taken into orbit around the Moon during Apollo 14)? Cast your vote below, or if you have a suggestion for a different topic, leave a note in the comments :)
Kozyrovska, N. O., Lutvynenko, T. L., Korniichuk, O. S., Kovalchuk, M. V., Voznyuk, T. M., Kononuchenko, O., … & Kordyum, V. A. (2006). Growing pioneer plants for a lunar base. Advances in Space Research, 37(1), 93-99.
In my occasional series, “When Plants Attack” we’ve seen some of the ways in which plants can defend themselves. So far I’ve covered the chemicals they produce to discourage other plants from growing in their space (allelopathy) and the conventional weaponry they use to guard against a physical attack. I am planning more posts to continue the series, which will include a look at the chemical defences plants have evolved to protect themselves against being eaten. But as soon as a plant evolves a defence mechanism, predators will begin to evolve or develop a way to counteract it. For example, some insects can collect poisons from the plants they’re munching on, and use them as part of their own defences. But until now it has seemed as though plant-eating mammals change their behaviour to cope with toxic plants – e.g. by changing how they forage for food, or by eating dirt (geophagy) to detox.
On Wednesday a paper published in Biology Letters put forward what the authors believe is the first evidence of large mammals evolving to combat a plant’s chemical defences. The researchers collected saliva samples from moose (Alces alces) and European reindeer (Rangifer tarandus) in Canadian zoos, whilst the animals were anesthetized to undergo necessary medical procedures. These two animals are known to feed on red fescue (Festuca rubra), a grass which occurs around the world. Red fescue uses a common defensive strategy: it forms a mutually-beneficial relationship with a fungus (Epichloë festucae), which produces toxic alkaloids.
By applying the animal saliva to grass samples, the researchers demonstrated that both moose and reindeer saliva slowed down the growth of the fungus, and so reduced the amount of toxin that was produced. Moose dribble also appeared to directly affect the levels of the toxin in European samples of the grass (the deployment of chemical defences depends on the environment in which the plant is grown), and the scientists theorize that the saliva is preventing the plant’s defence system from activating, by disrupting its signals.
So it seems that moose and reindeer aren’t just coping with the toxins produced by their diet of red fescue, but have evolved to actively combat them. “Plants have evolved defense mechanisms to protect themselves, such as thorns, bitter-tasting berries, and in the case of certain types of grass, by harbouring toxic fungus deep within them that can be dangerous or even fatal for grazing animals,” says York University’s Professor Dawn Bazely, who worked with University of Cambridge researcher Andrew Tanentzap and York University researcher Mark Vicari on the project. “We wanted to find out how moose were able to eat such large quantities of this grass without negative effects.” This interesting discovery (which will have to be verified by further studies) may seem a little esoteric, but you never know when you might need an enzyme that deactivates a toxic alkaloid (and this particular one also appears in ergot), and when you do it’s good to know that moose happen to have one handy.
You may also be fascinated to learn, as I did during the course of my research for this blog post, that whilst the common usage of “ungulates” refers to hoofed mammals (such as moose, reindeer, cattle and camels), cetaceans (whales, dolphins and porpoises) are also ungulates, sharing a common ancestor with the other species in this large group of mammals.
In this video from the University of Cambridge, Rox Middleton shows us a ‘nanoscale’ image of gum arabic, taken with an electron microscope. Gum arabic is the hardened sap of an Acacia tree; this sample was probably collected in Sudan. If you want to see what it looks like on the everyday scale, I took a photo of a chunk when I visited the Oxford University herbarium. Gum arabic is a food additive, E414, used as a stabiliser. It’s also used in paints and pigments.
This isn’t a fantasy alien landscape, its an image of a mint leaf, taken with a scanning electron microscope by Annie Cavanagh. This low-res version is available from Wellcome Images with a Creative Commons license, which allows me to show you how awesome plants are. The spike is a trichome (a hair, essentially). The blobs are oil, sitting on oil glands, and are what gives mint is delicious flavour. The oval structures that look a bit like seeds scattered on the surface, are stomata, the holes that the plant can open and close to regulate its intake of carbon dioxide and the expulsion of oxygen. You can just see the slits along the centre, which is where they would open up.
As I mentioned a few weeks ago, NASA astronaut Steve Swanson has been doing some gardening on the International Space Station, growing ‘Outredgeous’ red romaine lettuce in the new VEGGIE gardening system. This inaugural experiment, called Veg-01, is partly a test of the hardware and partly to see whether space-grown crops will be safe to eat. After all his hard work, Steve doesn’t get to eat his lettuce – it has to be returned to Earth for testing. If the lettuce is proved safe, a second batch of lettuce can be grown and eaten later in the year. This would be the first mouthful of ‘homegrown’ food to be consumed in space, and NASA have produced a great video explaining the VEGGIE project: