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.
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.”
astronaut Someone trained to travel into space for research and exploration.
astronomy The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.
Cassini A space probe sent by NASA to explore the planet Saturn. Cassini was launched from Earth in 1997. It reached Saturn in late 2004. The craft included a variety of instruments meant to study Saturn’s moons, rings, magnetic field and atmosphere.
Enceladus The sixth largest of Saturn’s more than 50 moons. Enceladus is bright white and covered with a thick shell of ice. Deep beneath that ice sits what appears to be a global ocean of salty liquid water. Enceladus is a round sphere, 500 kilometers (310 miles) across. It is a little less than one-third the width of Earth's moon.
Europa One of the moons of Jupiter and the sixth-closest satellite to the planet. Europa, 1,951 miles across, has a network of dark lines on a bright, icy surface.
fuel cell A device that converts chemical energy into electrical energy. The most common fuel is hydrogen, which emits only water vapor as a byproduct.
Jupiter (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
moon The natural satellite of any planet.
NASA Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.
nitrogen A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn.
particle A minute amount of something.
persistent An adjective for something that is long-lasting.
phosphorus A highly reactive, nonmetallic element occurring naturally in phosphates. Its scientific symbol is P. It is an important part of many chemicals and structures that are found in cells, such as membranes, and DNA.
planetary science The science of planets other than Earth.
plume (in geology) Fluids (air, water or magma typically) that move, largely intact, in a feather-like shape over long distances. (in environmental sciences) The movement of some gas or liquid, under the direction of gravity, winds or currents. It may be in air, soil or water. It gets its name from the fact that it tends to be long and relatively thin, shaped like a large feather.
Saturn The sixth planet out from the sun in our solar system. One of the four gas giants, this planet takes 10.7 hours to rotate (completing a day) and 29 Earth years to complete one orbit of the sun. It has at least 53 known moons and 9 more candidates awaiting confirmation. But what most distinguishes this planet is the broad and flat plane of seven rings that orbit it.
sulfur A chemical element with an atomic number of sixteen. Sulfur, one of the most common elements in the universe, is an essential element for life. Because sulfur and its compounds can store a lot of energy, it is present in fertilizers and many industrial chemicals.
vacuum Space with little or no matter in it. Laboratories or manufacturing plants may use vacuum equipment to pump out air, creating an area known as a vacuum chamber.
waste Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.
Meeting: R. Lorenz. Space toilets and ocean worlds: What spacecraft water dumps tell us about plumes on Enceladus and Europa. American Astronomical Society Division of Planetary Sciences Meeting, Provo, Utah, October 17, 2017.
Journal: H. Yano et al. Origins of micro-craters on the SFU spacecraft derived from elemental and morphological analyses. Advances in Space Research. Vol. 25, 2000, p. 293. doi: 10.1016/S0273-1177(99)00947-3.