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Plants in space hold the key to deep space exploration

Growing healthy, nutrient-rich plants in space is essential to provide fresh food to astronauts. Image credit: Thales Alenia Space/Stefano D’Amadio
Growing healthy, nutrient-rich plants in space is essential to provide fresh food to astronauts. Image credit: Thales Alenia Space/Stefano D’Amadio

Space farming is difficult business – plants don’t grow well in zero gravity and harsh radiation damages seeds – but if researchers can get it right, it could provide food, clean water, and oxygen for manned missions far from earth.

Lettuce, peas and radishes have been grown aboard the International Space Station for years, but electric-only light is detrimental to plant growth, and circulating gases need to be constantly swept away to let plants to breathe.

Low gravity alters plants too, stopping air and water from circulating around the roots in the way it would here on earth, while radiation can alter the DNA of seeds produced in space.

Researchers are already working on miniature ‘space greenhouses’ for the International Space Station that can help solve these problems.

Capillary action

A team of EU researchers is planning to grow the plants in a material filled with tiny, porous tubes. That means food and water will flow to the roots along these tubes by capillary action—taking advantage of the ability of liquid to automatically flow into narrow spaces.

The EU-funded project, called EDEN ISS, is also working on an intelligent lighting systems, using LEDs linked to state-of-the-art software that monitors plant growth and behaviour to control the illumination levels appropriately.

Before shooting off into space, plant cultivation technology developed by the EDEN ISS project will have to endure a year in isolated, hostile conditions at the Neumayer Station III in the Antarctic. This mobile testing facility will increase the readiness of the technology for the ISS, checking the kit’s ability to produce safe, quality food and self-manage any problems.

‘Our focus is on improving the performance of the illumination system, the nutrient delivery system and the bio-detection and decontamination system.’

Paul Zabel, the German Aerospace Centre (DLR)

‘Plant scientists at the University of Wageningen (the Netherlands) are currently selecting the different species that’ll go into the Antarctic container, and then we’ll look at how their selections influence the type of lighting required,’ said Anthony Gilley, chief technology officer at lighting company Heliospectra, which is a participant in the project.

Ensuring the plants are safe to eat is another major aim of the project and a relatively new field of research.

‘First of all, we’ll need to characterise the microbial environment in the greenhouse,’ said Paul Zabel, an engineer based at the German Aerospace Centre (DLR), which is coordinating EDEN ISS. ‘Sanitisation then depends on those measurements and on the standards you apply on food safety and quality.

‘Our focus is on improving the performance of the illumination system, the nutrient delivery system and the bio-detection and decontamination system.’

  • Stress molecules will alert the astronauts if the plants are feeling ill. Image credit: Thales Alenia Space/Stefano D’Amadio
  • Scientists also monitor the greenhouse for unwanted stressors like microbial activity. Image credit: Thales Alenia Space/Stefano D’Amadio
  • Plant greenhouses will allow food and water to be pumped into plant roots via tiny tubes, and intelligent lighting systems make plants grow better. Image credit: Thales Alenia Space/Stefano D’Amadio
  • Ensuring that the plants are safe to eat is a main aim of the EDEN-ISS project. Image credit: Thales Alenia Space/Stefano D’Amadio

Cress, lettuce

In order to measure the environment within the greenhouse, another team of researchers is working on a chamber capable of cultivating cress, lettuce and dwarf tomatoes which will include sensors and imaging techniques to monitor nutrient levels and record plant health metrics.

One of the things they’ll be looking out for are stress molecules that alert astronauts if the plants are feeling space sick.

‘We have to tailor our analytical method so that it can detect the target components from the earliest stage of plant development,’ said Joeri Vercammen, whose team at manufacturer Interscience are working on the monitoring technology, as part of the EU-funded project, known as TIME SCALE.

The highly sensitive machinery can analyse airborne molecules which are emitted by plants in conditions such as drought and salinity.

It’s still early days for the projects, which both started earlier this year, but the work they are doing will be vital when humans undertake their first trip out into the solar system, beyond the reach of supply rockets.

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