Space toilet may teach scientists how to scout for life on distant icy moons

Flushing away pee on the space shuttle simulates the plumes of icy moons, one scientist suggests

This is an illustration of a space shuttle being hoisted into space. Crews aboard the craft used a special toilet to do you know what. The process used to flush those wastes away may offer lessons about venting other liquids in space — by celestial objects.


The search for life may get an assist from the call of nature. Astronomers have been intrigued by jets of icy liquids, such as on Saturn’s moon Enceladus. Now they might learn how to study such plumes from an unlikely source: space toilets.

Enceladus hosts an ocean of liquid water beneath its icy surface. That sea constantly vents water into space through cracks in its surface ice. (Jupiter’s moon Europa also hosts an ocean of liquid water beneath its icy surface. So it, too, may spew plumes. But if it does, those plumes are not as persistent.) Planetary scientists would like future spacecraft to scoop up samples of these plumes. That way they could test them for signs of life. But trying to model such space plumes in a lab on Earth is challenging.

This was the toilet on space shuttle Columbia. NASA says the system worked “like a vacuum cleaner with fans that suck air and waste into the commode.” Each astronaut had a personal urinal funnel (gray in center of photo), which had to send the waste to a collection tank.NASA

The good news: Astronauts have already done natural experiments in venting water to space. It’s something Ralph Lorenz described on October 17. He’s a researcher at Johns Hopkins University in Baltimore, Md. Lorenz worked on NASA’s Cassini mission to Saturn. He’s now helping design future missions to Saturn’s moons. And in a talk at the American Astronomical Society’s Division of Planetary Sciences meeting in Provo, Utah, he noted that spacecraft frequently vent water into the vacuum of space. Sometimes it comes from fuel cells. Every time an astronaut flushes a space toilet also releases a plume of water into space.

During the first flight of the space shuttle Discovery in 1984, for example, an icicle grew from a fuel-cell vent. It lengthened to 60 centimeters (23.6 inches). Astronauts eventually had to knock it off with the shuttle arm. That experience could hint at how the water vents on Enceladus change shape over time — and how big the ice particles spewed by those vents can get.

A 2000 paper in Advances in Space Research analyzed small dents on a Japanese spacecraft. It found traces of phosphorus, sulfur and nitrogen. The authors concluded these may have been from particles of urine ice raining down on the exterior of the craft. (Yeah, yuck!)

But that, Lorenz says, might spell good news in the hunt for signs of life on Enceladus. Future space missions could look for molecules associated with life that have been preserved in plumes of ice spewed by this moon.

“It’s all the same problem,” Lorenz says. “I think there are some things to be learned to apply to Enceladus from human spaceflight.”

The process that forces water out of flushed toilets on the space shuttle also makes vents on Saturn’s moon Enceladus gush the liquid plumes (shown).SSI/JPL/NASA, EMILY LAKDAWALLA (MOSAIC)

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

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