MyBlackBeasts
03-16-2013, 03:15 PM
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Adhesion – the physics of Space Gardens
Adhesion is the force of attraction between atoms or molecules of different substances. One example of this is the adhe...sion between glass and water molecules – resulting in the creation of a meniscus.
Adhesion occurs in space, but other forces (like gravity) are less powerful. This allowed Nikolai Budarin to take this image in the Russian Lada greenhouse on the International Space Station (ISS).
The stalk supports a drop of water – without bending under its weight. Furthermore, a bubble of air sits suspended, trapped within the droplet.
If this scenario was to occur on Earth, the air bubble (which is lighter than water) would move to the top, and burst through the skin of the droplet. The leaf would bend, tipping the water to the ground below. This scene would only last for the briefest instant and would be near impossible to capture on camera.
In space, however, the air bubble doesn't rise because there's no buoyancy. The force of molecular adhesion sticks the droplet to the leaf – there's no other force to pull it off.
These scenarios force careful consideration of gardening on the ISS. If you water a plant, the moisture may not make it to the root system – but stick to the stalk instead. Oxygen created by the plant lingers around, inhibiting new carbon dioxide from getting close to the plant – this can cause the plant to suffocate.
-CJ
Further Reading:
http://www.nasa.gov/audience/forstudents/5-8/features/space_gardens_feature.html
NASA video: Cohesion and Adhesion on-board the ISS (~5min):
http://www.nasa.gov/audience/foreducators/topnav/schedule/programdescriptions/Eclips_Cohesion_Adhesion_ISS_9-12.html
Image: Nikolai Budarin, 2003
Adhesion – the physics of Space Gardens
Adhesion is the force of attraction between atoms or molecules of different substances. One example of this is the adhe...sion between glass and water molecules – resulting in the creation of a meniscus.
Adhesion occurs in space, but other forces (like gravity) are less powerful. This allowed Nikolai Budarin to take this image in the Russian Lada greenhouse on the International Space Station (ISS).
The stalk supports a drop of water – without bending under its weight. Furthermore, a bubble of air sits suspended, trapped within the droplet.
If this scenario was to occur on Earth, the air bubble (which is lighter than water) would move to the top, and burst through the skin of the droplet. The leaf would bend, tipping the water to the ground below. This scene would only last for the briefest instant and would be near impossible to capture on camera.
In space, however, the air bubble doesn't rise because there's no buoyancy. The force of molecular adhesion sticks the droplet to the leaf – there's no other force to pull it off.
These scenarios force careful consideration of gardening on the ISS. If you water a plant, the moisture may not make it to the root system – but stick to the stalk instead. Oxygen created by the plant lingers around, inhibiting new carbon dioxide from getting close to the plant – this can cause the plant to suffocate.
-CJ
Further Reading:
http://www.nasa.gov/audience/forstudents/5-8/features/space_gardens_feature.html
NASA video: Cohesion and Adhesion on-board the ISS (~5min):
http://www.nasa.gov/audience/foreducators/topnav/schedule/programdescriptions/Eclips_Cohesion_Adhesion_ISS_9-12.html
Image: Nikolai Budarin, 2003