Worms were the only survivors when space shuttle Columbia broke up on re-entry in 2003. Caenorhabditis elegans, nematodes, had been sent into space to test a synthetic nutrient solution. Their naturally short life-span meant that the survivors were several generations removed from the worms that were blasted into space at the beginning of the mission. Nematodes experiments have also been conducted on the International Space Station (ISS), looking at the effect of microgravity – it turns out that these worms can suffer muscle mass loss in the same way as humans do. Nematodes weren’t the only worms included on that fateful mission; among the student experiments (which included space bees) was one that aimed to investigate mealworms (Tenebrio molitor). Sadly they didn’t survive.


Composting worms
Composting worms, at work on Earth

Small organisms such as these are very useful for bioscience research in space, but there are other reasons why worms might be a key feature of future space adventures. When the latest Antares supply mission to the ISS suffered a ‘launch mishap’ at the end of October, another student experiment – to investigate whether worm composting works in space – went up in smoke. The students wanted to find a way to recycle leftover astronaut food, and were sending redworms (Eisenia fetida) into space – the same worms you’re using here on Earth if you have a worm composter. Fortunately, the students have been told they will get another chance to run their experiment.


Composting worms can help to dispose of waste food because they can eat things we can’t, and including animals and insects into closed-loop agricultural systems in space is one way of completing the cycle and turning waste products into inputs. They can be used to improve the soil and produce fertiliser, or to turn inedible biomass into protein to enhance the astronaut’s diet. But adding animals into the system can be tricky – not only are they large and heavy (hence expensive to launch into space), but they produce waste gases and some of them would stink out closed quarters. Plus you have to factor in the time spent looking after animals, when astronauts are already busy. Aquatic animals such as fish are also being considered, but bring their own set of problems to overcome.

And so the idea of raising edible insects in space arises. These ‘microlivestock’ can be easily and cleanly raised on waste products, and produce little in the way of waste themselves (and frass , worm poop, makes good fertiliser). Insects are already eaten in some cultures on Earth, although for most people they are decidedly not on the menu.


Main course
An appetising plate of edible insects

Two of the most studied species are silkworms (Bombyx mori) and mealworms, which are beetle larvae.

Katayama et al point out that insects were an important portion of the hunter-gatherer diet. Perhaps the Paleo diet people should be taking a look….


Silkworm pupae
Yummy looking silkworm pupae

Yang et al write about the history of silkworm consumption in China and state that silkworm culture won’t have adverse effects on the cabin environment. They also say that silkworm fibre (I assume they mean silk) is over 98% protein and could be hydrolysed into an edible product. I’m not sure anyone would find that more appetising than the silkworms themselves.

Yu et al propose a simple bioregenerative life support system involving mulberries and silkworms. The mulberries would provide fruit for astronauts, plus leaves to feed silkworms. The silkworms could also eat the leaves of stem lettuce – stem lettuce is a popular Chinese vegetable, but the leaves aren’t eaten (and seem to be considered inedible). 105 silkworms would provide the daily protein requirements for an astronaut (a Chinese astronaut, or taikonaut – they note that the Russians have double the protein requirement!). The silkworms can be eaten as pupae or as powdered larvae (which has the advantage of not having to deal with cocoons). Yum.

Beyond that being a slightly dull diet, I fail to see how mulberry trees would make good candidates for space cultivation, being large trees. You could take seeds, I suppose, so they blast-off weight would be small, but then you’d have to wait years for the trees to mature….

“The height and diameter of ground-controlled mulberry tree were much lower than other kinds of fruit trees. Lower trunk shortened the distance of transporting nutrient and water, accelerated the growth of branches and leave and improved the efficiency of photosynthesis.”

Li et al note that silkworms have a limited waste disposal role, as they only eat the leaves of stem lettuce and mulberry leaves. They investigated mealworms as an alternative, feeding them wheat straw and vegetable waste (and wheat is one of the ‘big 3’ cereal crops on Earth that produce most of our calories, so being able to grow it in space would be useful). Mealworms can be fed a variety of plant material.


Starter
Mealworms, with a side of mole crickets

And earlier this year, three volunteers spent three months inside Moon Palace 1 (Yuegong-1), an artificial biosphere in Beijing designed to test the kind of life support system that may one day be used for a long duration space mission. They grew grain, vegetables and fruit and fed the crop wastes to mealworms. They ate dozens of mealworms each day, trying out different cooking styles and seasonings. No doubt we can expect them to publish a cookbook very soon!

Mealworms may not be the best choice, though – the HI SEAS project decided against them as they are “little escape artists”, something I have personal experience of. I used to have a regular delivery of live mealworms to feed the garden birds. I can just imagine how the postman felt when he delivered the damaged box from which they were all escaping…. Some scientists feel that freshwater algae could deliver the same benefits, but that’s a topic for another post 🙂


References

Katayama, N., Yamashita, M., Wada, H., & Mitsuhashi, J. (2005). Entomophagy as part of a space diet for habitation on Mars. The Journal of Space Technology and Science, 21(2), 2_27-2_38.

Kramer, M. (2013). How Worms Survived NASA’s Columbia Shuttle Disaster. Space.com [Online]. Accessed 9th November 2014.

Li, L., Zhao, Z., & Liu, H. (2013). Feasibility of feeding yellow mealworm (Tenebrio molitor L.) in bioregenerative life support systems as a source of animal protein for humans. Acta Astronautica , 92(1), 103-109.

Rutkin, A. (2014). Space hopefuls dine on worms in ‘Moon Palace’ module. New Scientist. [Online]. Accessed 9th November 2014.

Space Today Online. (2006). Tragedy of Space Shuttle Columbia. Space Today. [Online: http://www.spacetoday.org/SpcShtls/ColumbiaExplosion2003/ColumbiaExplosion.html]. Accessed 9th November 2014.

Yang, Y., Tang, L., Tong, L., & Liu, H. (2009). Silkworms culture as a source of protein for humans in space. Advances in Space Research, 43(8), 1236-1242.

Yu, X., Liu, H., & Tong, L. (2008). Feeding scenario of the silkworm Bombyx Mori, L. in the BLSS. Acta Astronautica, 63(7), 1086-1092.