There are no blooming marigolds on the ISS

In August this year, astronaut Thomas Pesquet was about to start an experiment on International Space Station (ISS). 'Graines d’Eklo' involved a specially-designed growing capsule, containing its own light source and a growing medium made of coir (coconut fiber) and vermiculite with a slow-release fertilizer.

Pesquet’s role was to add water to the capsule via a valve in the base, which would allow the French marigold seeds inside to germinate, eventually growing into plants that would bloom in space.

The team behind the experiment chose dwarf marigolds because they were small enough to grow within the space constraints of an ISS experiment. They would also happily grow in the ambient temperature onboard, germinate quickly, and flower in these unusual circumstances. Or that was the plan.

Here on Earth, people received kits or bought their own seeds to grow marigolds alongside Thomas. They shared pictures of their growing and blooming plants, using the hashtag #EklosionISS. Back on the ISS, however, the plants did not grow, let alone bloom. 

With the help of Thomas Pesquet and CNES, the ground team tried to understand why their space experiment had not worked. They determined that, after Thomas Pesquet had added the first dose of water, the capsule had been moved before the coir absorbed the liquid. 

This was an unfortunate consequence of a crowded space station environment. With space at a premium, Pesquet had to keep moving the capsule around. As a result, the unabsorbed water rose up through the capsule and suffocated the seeds, preventing their development. Pesquet’s best efforts could not keep the experiment alive.

Although this turn of events is disappointing, the experiment is still a valuable learning experience. The lighting system worked well, and the capsule remained watertight. Clearly, there are some issues using coir in space, but perhaps they can be overcome in the future.

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