April 1, 2003

Space Bubbles
Photo credit: Ken Bowersox, ISS Expedition 6 Commander, NASA

Explanation: "One time I sent a marble-sized drop of water from my shower off on its own trajectory," says ISS Science Officer Don Pettit. "It was filled with tiny bubbles. Like a little planet, the drop was spinning on its axis. I observed that all the bubbles quickly moved to the center and formed a line along the axis of rotation." The spinning droplet was like a miniature centrifuge: Higher-density water was flung away from the spin axis; lower-density air bubbles sank toward it. Scientists here on Earth are thinking about spinning entire spaceships to provide artificial gravity for astronauts. Space station shower droplets are a fun model for that grander project. After his shower, Don wondered what would happen if he spun water droplets containing not lightweight air bubbles, but instead particles like tea leaves and sugar grains, which are denser than water. Can you guess? Read Don's Space Chronicle #5 to find out what happened.

Editor's note: There is no shower on the ISS that resembles a bathroom shower on Earth. Astronauts use spray nozzles to squirt water on wash cloths--that's how they clean themselves. The spray nozzle is what Don Pettit meant by "my shower."