Chemical Gardens in Space

A classic laboratory investigation is being conducted aboard the International Space Station to better understand gravity's impact on nanotube growth in chemical gardens. Here on Earth, colorful crystal chemical gardens are often used to teach students about phenomena like hydrothermal vents and chemical reactions. Although completely inorganic, these gardens resemble plants and are influenced in their development by the pull of gravity. Chemical gardens form when dissolvable metal salts are placed in an aqueous solution containing anions such as silicate, borate, phosphate, or carbonate. The most common solution used is sodium silicate, and when the two are introduced, precipitation structures can form within minutes. The result is a vine-like array of buds, limbs and tubes. Gardens can range in color depending on the chemicals used.

Delivered to the space station aboard SpaceX CRS-15, astronauts will process the samples for an investigation called Understanding Growth Morphologies in Chemical Gardens (Chemical Gardens) and grow them throughout Expedition 56 before returning the results to Earth for full study.

"We expect macroscopic and microscopic morphology changes," said Chemical Gardens' researcher and doctoral candidate Alexander Blanchard. "While on-Earth growth tends to be upward, we expect growth in random directions and a spherical shape in space at the macroscopic level."

Once the investigation's in-orbit phase is complete, samples will be returned to Marshall Space Flight Center, home base for the Chemical Gardens research team. Here, samples will be photographed extensively at the macroscopic and microscopic level.

"We will use a scanning electron microscope to look at morphology," said Chemical Gardens' co-investigator Ellen Rabenberg. "This lets us see at up to 5,000x or 10,000x magnification as opposed to the 50x or 100x you would see from optical microscopes." This imagery will allow every aspect of the gardens to be studied in great detail.

While this is not the first set of chemical gardens grown in space, the proposed experiments could expand our knowledge of this phenomena.

"Being able to isolate pressure in the absence of buoyancy could allow us to better understand their growth and tailor them to specific applications and give us further insight into reaction-diffusion chemical systems and self-organization," said Blanchard.

Applications from this investigation could include a better understanding of cement science and corrosion, potential improvements for tube walls for catalytic applications, and improvements to biomaterial devices used for scaffolding and compatibility with living cells and tissues.

In space, chemical gardens could be grown to create similar scaffolds and thorough study of microgravity's effect will allow for better control of the gardens' growth.