In 2019, Nickelodeon sent green slime to the ISS for eight demonstrations; the tests offered insights into liquid containment and hydroponic plant watering research

In the summer of 2019, astronauts aboard the International Space Station did something unexpected for trained scientists: they played with slime. According to NASA, the space agency teamed up with the kids' television channel Nickelodeon and ISS National Laboratory to launch packets of green slime into space, turning a childhood classic into a real physics experiment. The idea might sound silly, but the data it produced was not.

From a kids' TV gimmick to a physics experiment

For decades, Nickelodeon has been covering the heads of celebs in its signature slime, from Kids' Choice Awards winners to Slime Time Live contestants. And so, when the network wanted to send the goo into space, it needed real scientists to design the experiments. That was the job of Mark Weislogel, a mechanical engineering professor at Portland State University, and his graduate research assistant, Rihana Mungin. Writing for the ISS National Laboratory, the two researchers explained that sending such a large amount of highly viscous liquid to the space station was such a unique opportunity that it would have been a mistake not to learn as much as possible from it.

The slime went to orbit aboard SpaceX's 18th commercial resupply mission to the station with a set of super-hydrophobic ping pong paddles, paddles specially coated to repel water, according to the ISS National Laboratory. Once on board, NASA astronauts Christina Koch and Drew Morgan and European Space Agency astronaut Luca Parmitano took turns testing how the slime behaved in a zero-gravity environment, stretching and bouncing without gravity to hold it down.

Eight demonstrations and one accidental sliming

Slime is a non-Newtonian fluid, meaning its viscosity changes depending on the force exerted on it. According to CNN's report of the experiment, the slime taken up into space was about 20,000 times thicker than water, and thus it didn't resemble a splash of juice floating through the cabin. ISS National Laboratory reports that the astronauts performed at least eight demonstrations, and they even included one surprise demonstration. They tested how slime and water behave while floating in space. They spun both liquids, tried to cut the slime using dental floss, and created slime bubbles using syringes. During one of their experiments, in the scientists' description, a stream of slime that was released from a syringe pierced a slime bubble in front of Parmitano and he became the first person ever to be slimed in space. At some point, they directed the stream of slime towards Koch with the help of a paddle. They popped slime-filled balloons and, in an unplanned finale, Parmitano brought two slime-coated paddles together and slowly pulled them apart, forming a long liquid bridge that broke into five perfectly placed satellite droplets, a phenomenon Mungin said she'd previously only observed under a microscope, at a scale a thousand times smaller and over a thousandth of a second.

Why scientists actually cared about the goo

Behind the fun, each demonstration was carefully put together in order to collect actual data on how the density, surface tension, and viscosity of the slime behaved without the effects of gravity. The ISS National Lab article explains that handling liquids is more complicated in space than people realize because the devices used to work with liquids, which rely on gravity, such as watering plants, boilers, and condensers, simply don’t function the way engineers expect once weightlessness sets in.

According to NASA's account of the project, the lessons learned were intended to support future space technologies, especially low-gravity droplet creation, reduction, and containment. NASA also said the findings could help with liquid containment and hydroponic plant watering in space. In other words, watching astronauts wrestle with cartoon slime helped researchers understand problems that matter for growing food and managing fluids on future long-duration missions.

A lesson dressed up as a prank

Besides the science, the project had an educational goal. NASA says the experiment produced a fifteen-minute online field trip for students in grades three through five that, as of NASA's most recent public count, has been viewed more than 600,000 times. For a generation that grew up with Nickelodeon's slime as a symbol of awards-show pranks, watching that same goo be used to study fluid physics in orbit was an unusually memorable science lesson. It is easy to laugh at the idea of NASA astronauts getting slimed on purpose. But the Slime in Space project, as the ISS National Laboratory frames it, is a reminder that even the silliest experiments can generate useful data, as long as someone is paying close attention to the physics underneath the mess. The next time you see a spacecraft's water system or a plant growing chamber designed for a future Mars mission, there is a decent chance the engineers behind it once studied a floating blob of neon green goo.