To Boldly Go: The Science Behind Pooping in Space


What Mike Mullane remembers most clearly about having his first bowel movement in space is the blast of cold air greeting his exposed rectum. Over the course of three week-long NASA shuttle missions in the 1980s—two for Discovery, one for Atlantis—Mullane was forced to answer nature's call six or seven times in zero gravity. Each time, he would have to strip naked, close a flimsy curtain around a titanium commode, position his buttocks to form a perfect seal around a 4-inch opening, and then follow a checklist posted nearby to make sure no fecal particles escaped into the deck—all while his sphincter insisted on clamping shut to escape the freezing temperatures.

"It was a complex operation," Mullane tells Mental Floss. "On Earth, I'm fast. My wife is amazed I can be in and out of the bathroom in one minute for a number two. On the shuttle, it would take 30."

While the industrial toilet was a far cry from five-star hotel room seat warmers and bidets, it also improved by magnitudes the ordeal of emptying one's intestines in zero gravity. Prior to 1972, the men of the Gemini and Apollo missions braved poop bags that they would stick to their rear ends, then manually knead the contents with an antibacterial solution so the gases wouldn't detonate the collection; more than one crew has been terrorized by rogue turds hovering in the air.

Coming up with a practical way of replicating the earthbound poop experience took many years, many engineers, and a whole lot of ingenuity. While few explorers like to discuss it, taking a space dump is its own kind of heroism.

Consider one early—and discarded—solution for waste collection in space, which someone dubbed the "sh*t mitt." Donald Rethke likens it to "those long rubber gloves veterinarians use for insemination." The idea, he tells Mental Floss, was that the astronaut could poop in their own hand and then turn the glove inside-out, creating instant containment of the feces.

Now 80, Rethke is a retired engineer from Hamilton-Standard, a NASA subcontractor working through Northrop Grumman that spent decades refining or pioneering life-support systems for space explorers. Rethke, who embraces his industry nickname of "Doctor Flush," says that handling poop simply wasn't much of a concern due to the brief trips taken by pioneering astronauts: They could just go before they left. But as missions grew longer, it became necessary to address personal waste—urine and bowel movements—without dealing with the discomfort of diapers.

A NASA training commode
A training toilet with a camera positioned inside so astronauts can learn how to best angle their buttocks.
National Geographic, YouTube

For the 1965–66 Gemini excursions, which were planned to prove humans could survive for several days or weeks in space, astronauts were told to use a condom-like sheath that would direct urine into a bag. For feces, they were to use a pouch with a 1.5-inch opening and an adhesive strip around the edge to help prevent fecal matter from escaping. A fellow crew member would be told to stand by and watch to make sure no waste escaped into the capsule.

"It kind of looked like an upside-down top hat," Mullane says. Though they pre-dated his missions, they were on board his shuttles in case of equipment failure. "We never had to use them, thank God."

But the occupants of Gemini and Apollo did, and most found it unpleasant for reasons unrelated to crapping in a bag. When gravity is lacking, surface tension becomes a dominant force. So urine and feces that would separate from the body on Earth thanks to gravity tend to cling to the skin's surface in space.

"If you stick your finger into a glass of water and lift it up, water flows off," Mullane explains. "But in weightlessness, the attraction of the molecules of the fluid will pull it into a ball. If you leave fluid alone, it will form a perfect sphere. Touch it, and will stick to you."

The same goes for poop. The bags had tiny finger covers built in so users could flick and scrape errant flecks away from their cheeks. Then they'd mix in a chemical to kill the bacteria so the gases wouldn't expand in the sealed bag and create an explosive biohazard.

"Well, it's in a small, like a ketchup, a little plastic container like you find ketchup in in restaurants, in a cafeteria or something, it's like that," Apollo astronaut Russell Sweickhart told a reporter in 1977. "You tear the slit across the top, being careful not to squeeze it so the stuff comes out, and then you drop that into the fecal container, and then seal the fecal container. Then you squeeze it through the, you know, externally, you know, which forces it out of the container, and then you mix it by massaging the fecal bag. It's really fun when it's still warm."

If everything went well, it was merely disgusting. If it didn't, as the following transcript excerpt from the 1969 Apollo 10 mission demonstrates, it could be highly disruptive:

Tom Stafford: Give me a napkin quick. There's a turd floating through the air.

John Young: I didn't do it. It ain't one of mine.

Gene Cernan: I don't think it's one of mine.

Stafford: Mine was a little more sticky than that. Throw that away.

Young: God Almighty.

"When the Apollo astronauts came back," Rethke says, "they wanted sit-down toilets."

A look at the ISS bathroom
The "orbital outhouse" inside the International Space Station.

While modesty may not have been an achievable goal, astronauts needed some semblance of routine. (Some shuttles were equipped with kitchen tables, even though nothing in zero gravity could be perched on one.) But the comforts of a domestic commode had little application in space. No water could be used: It would run everywhere. And unlike gravity-assisted toilets, a shuttle john would have to address the surface tension issue that enticed poop to come out in curls instead of straight down, mashing itself against the skin.

The solution, according to Rethke, was gentle suction. "Or, as I like to call it, air entrainment," he says. In its simplest form, it's getting the poop Hoovered away from your bottom using air flow as a substitute for gravity.

Rethke says the idea was already on the table courtesy of General Electric (GE) when Hamilton-Standard began working on a zero gravity toilet, and that his job was one of refinement that lasted through the 1980s and 1990s. "The concept of separating solids from the body was already in the bag, no pun intended. It was just the best way. Most of my effort was how to do that economically."

NASA had previously toyed with a variety of designs, including one 1971 model that was mounted vertically on a wall to conserve space. Another took the feces and pulped it, a model not unlike evacuating into a blender. This, engineers realized, created the potential for fecal "dust," or powdered particles of poop, that could contaminate the cabin of spacecraft. By using air entrainment, hardly anything could escape the bowl—and if it did, it wouldn't be atomized to the point of being a biological hazard. Instead, a fan and vacuum system was used to encourage the waste to settle at the bottom of the waste tube.

Air entrainment made one frustrating demand of its users: proper anal positioning. With a 4-inch opening compared to a conventional toilet's 18 inches, astronauts had to align themselves up perfectly in order to avoid any escaping feces. To train astronauts heading for space, NASA set up a commode with a camera mounted inside. (You were not expected to make a deposit.) Users could gauge their perch based on freckles or other skin marks in relation to the seat. Properly docked, they could poop on target, but it took practice.

"It's hard to know where your a-hole is when the hole is that narrow," Mullane says.

Minor complaints aside, NASA's work was ready in time for the 1973 debut of Skylab, the first space station, and the 1981 launch of Columbia, the first shuttle to reach space. After realizing the pulverizing model wasn't going to work due to the fecal dust issue and other malfunctions that led to problems on 10 of the shuttle's first 11 voyages, a redesigned system less prone to clogging was introduced in the mid-1980s.

Urinating, according to Mullane, was never any big deal. Men and women use a form-fitting cup and gentle suction to empty their bladder. "Pretty simple," he says. "But solid waste, that was kind of like going in a camper toilet."

On the Atlantis and Discovery, the space commode had foot rests and thigh straps so astronauts could remain secure to the seat while doing their business. They'd typically opt to strip naked in the event any soiling occurred. To the right was a hand lever; pushed forward, it slid open the tube underneath their buttocks. "You never wanted to open that before sitting on it," Mullane says. Doing so could release the previous user's residual fecal matter into the air.

Once Mullane was strapped in, he would open the tube cover and feel the rush of cold air hit his rear. The air moved 360 degrees while a fan underneath—loud enough to mask sounds of elimination—pulled waste away from the body and into a container that would store the matter until the shuttle returned. Toilet paper would go in a separate bag. By the time Mullane got dressed, cleaned the toilet's edges, and exited, 30 minutes had passed.

Surprisingly, the intimate size of the shuttle didn't contribute to any fragrant evidence. "They did a really good job of filtration," Mullane says. "You never smelled anything."

Rethke improved on this in the early 1990s by compacting the discarded feces at the bottom, reducing the need for storage space. (To make sure it would stay sealed, Rethke once kept a feces-filled container in his office for a year.)

Small tweaks aside, the space toilet doesn't follow the update schedule of, say, an iPhone. What Rethke redesigned and what Mullane used is, by and large, what's still in use on the International Space Station (ISS) today. But instead of bringing waste back, it's discarded so it burns up in the atmosphere.

Future movements may prove more difficult to handle. With the advent of long-duration travel, possibly to Mars, on the horizon, space exploration will have to deal with the issue of waste management when there's virtually no chance of Earthbound assistance.

"When toilets fail [on Earth], it's a real pain," Mullane says. "Just imagine that on Mars. I have no idea how they're going to do that."

Someone might. In early 2017, the HeroX platform crowned a winner in its Space Poop Challenge, which crowdsourced ways to handle waste in space when an explorer is in a spacesuit and away from a fixed toilet for long periods. The winning idea—a suit hatch that can be used to insert inflatable bedpans and diapers—earned inventor Thatcher Cardon a $15,000 prize. If it works, it'll assist in an integral part of exploring beyond our atmospheric borders. In space, everyone needs to go.

Additional Sources: Riding Rockets: The Outrageous Tales of a Space Shuttle Astronaut

15 Facts About Nicolaus Copernicus


Polish astronomer and mathematician Nicolaus Copernicus fundamentally altered our understanding of science. Born on February 19, 1473, he popularized the heliocentric theory that all planets revolve around the Sun, ushering in the Copernican Revolution. But he was also a lifelong bachelor and member of the clergy who dabbled in medicine and economics. Dive in to these 15 facts about the father of modern astronomy.

1. He came from a family of merchants and clergy.

Some historians believe that Copernicus's name derives from Koperniki, a village in Poland named after tradesmen who mined and sold copper. The astronomer's father, also named Nicolaus Copernicus, was a successful copper merchant in Krakow. His mother, Barbara Watzenrode, came from a powerful family of merchants, and her brother, Lucas Watzenrode the Younger, was an influential Bishop. Two of Copernicus's three older siblings joined the Catholic Church, one as a canon and one as a nun.

2. He was a polyglot.

Growing up, Copernicus likely knew both Polish and German. When Copernicus's father died when he was around 10, Lucas Watzenrode funded his nephew's education and he started learning Latin. In 1491, Copernicus began studying astronomy, math, philosophy, and logic at Krakow University. Five years later, he headed to modern Italy's Bologna University to study law, where he likely picked up some Italian. During his studies, he also read Greek, meaning modern historians think he knew or understood five languages.

3. He wasn't the first person to suggest heliocentrism ...

 A page from the work of Copernicus showing the position of planets in relation to the Sun.
A page from the work of Copernicus showing the position of planets in relation to the Sun.
Hulton Archive, Getty Images

Copernicus is credited with introducing heliocentrism—the idea that the Earth orbits the sun, rather than the sun orbiting the Earth. But several ancient Greek and Islamic scholars from various cultures discussed similar ideas centuries earlier. For example, Aristarchus of Samos, a Greek astronomer who lived in the 200s BCE, theorized that Earth and other planets revolved around the Sun.

4. … but he didn't fully give credit to earlier scholars.

To be clear, Copernicus knew of the work of earlier mathematicians. In a draft of his 1543 manuscript, he even included passages acknowledging the heliocentric ideas of Aristarchus and other ancient Greek astronomers who had written previous versions of the theory. Before submitting the manuscript for publication, though, Copernicus removed this section; theories for the removal range from wanting to present the ideas as wholly his own to simply switching out a Latin quote for a "more erudite" Greek quote and incidentally removing Aristarchus. These extra pages weren't found for another 300-some years.

5. He made contributions to economics.

He's known for math and science, but Copernicus was also quite the economist. In 1517, he wrote a research paper outlining proposals for how the Polish monarch could simplify the country's multiple currencies, especially in regard to the debasement of some of those currencies. His ideas on supply and demand, inflation, and government price-fixing influenced later economic principles such as Gresham's Law (the observation that "bad money drives out good" if they exchange for the same price; for example, if a country has both a paper $1 bill and a $1 coin, the value of the metal in the coin is higher than the value of the cotton and linen in the bill, and thus the bill will be spent as currency more because of that) and the Quantity Theory of Money (the idea that the amount of money in circulation is proportional to how much goods cost).

6. He was a physician (but he didn't have a medical degree).

After studying law, Copernicus traveled to the University of Padua so he could become a medical advisor to his sick uncle, Bishop Watzenrode. Despite spending two years studying medical texts and learning anatomy, Copernicus left medical school without a doctoral degree. Nevertheless, he traveled with his uncle and treated him, as well as other members of the clergy who needed medical attention.

7. He was probably a lifelong bachelor …

An etching of Copernicus, circa 1530.
An etching of Copernicus, circa 1530.
Hulton Archive, Getty Images

As an official in the Catholic Church, Copernicus took a vow of celibacy. He never married and was most likely a virgin (more on that below), but children were not completely absent from his life: After his older sister Katharina died, he became the financial guardian of her five children, his nieces and nephews.

8. … But he may have had an affair with his housekeeper.

Copernicus took a vow of celibacy, but did he keep it? In the late 1530s, the astronomer was in his sixties when Anna Schilling, a woman in her late forties, began living with him. Schilling may have been related to Copernicus—some historians think he was her great uncle—and she worked as his housekeeper for two years. For unknown reasons, the bishop he worked under admonished Copernicus twice for having Schilling live with him, even telling the astronomer to fire her and writing to other church officials about the matter.

9. He attended four universities before earning a degree.

A Polish stamp of Nicolaus Copernicus.

Copernicus spent over a decade studying at universities across Poland and Italy, but he usually left before he got his degree. Why skip the diplomas? Some historians argue that at the time, it was not unusual for students to leave a university without earning a degree. Moreover, Copernicus didn't need a degree to practice medicine or law, to work as a member of the Catholic Church, or even to take graduate or higher level courses. 

But right before returning to Poland he received a doctorate in canon law from the University of Ferrara. According to Copernicus scholar Edward Rosen this wasn't exactly for scholarly purposes, but that to "show that he had not frittered his time away on wine, women, and song, he had to bring home a diploma. That cost much less in Ferrara than in the other Italian universities where he studied."

10. He was cautious about publicizing his views.

During Copernicus's lifetime, nearly everyone believed in geocentrism—the view that the Earth lies at the center of the universe. Despite that, in the 1510s Copernicus wrote Commentariolus, or "the Little Commentary," a short text that discussed heliocentrism and was circulated amongst his friends. It was soon found circulating further afield, and it's said that Pope Clement VII heard a talk about the new theory and reacted favorably. Later, Cardinal Nicholas Schönberg wrote a letter of encouragement to Copernicus, but Copernicus still hesitated in publishing the full version. Some historians propose that Copernicus was worried about ridicule from the scientific community due to not being able to work out all of the issues heliocentrism created. Others propose that with the rise of the Reformation, the Catholic Church was increasingly cracking down on dissent and Copernicus feared persecution. Either way, he didn't make his complete work public until 1543.

11. He published his work on his deathbed.

An antique bookseller displays a rare first edition of Nicolaus Copernicus' revolutionary book on the planet system.
An antique bookseller displays a rare first edition of Nicolaus Copernicus' revolutionary book on the planet system, at the Tokyo International antique book fair on March 12, 2008. The book, published in 1543 and entitled in Latin "De Revolutionibus Orbium Coelestium, Libri VI," carries a diagram that shows the Earth and other planets revolving around the Sun, countering the then-prevailing geocentric theory.

Copernicus finishing writing his book explaining heliocentrism, De Revolutionibus Orbium Coelestium (On the Revolutions of Celestial Orbs), in the 1530s. When he was on his deathbed in 1543, he finally decided to publish his controversial work. According to lore, the astronomer awoke from a coma to read pages from his just-printed book shortly before passing away.

12. Galileo was punished for agreeing with Copernicus.

Copernicus dedicated his book to the Pope, but the Catholic Church repudiated it decades after it was published, placing it on the Index of Prohibited Books—pending revision—in 1616. A few years later, the Church ended the ban after editing the text to present Copernicus's views as wholly hypothetical. In 1633, 90 years after Copernicus's death, the Church convicted astronomer Galileo Galilei of "strong suspicion of heresy" for espousing Copernicus's theory of heliocentrism. After a day in prison, Galileo spent the rest of his life under house arrest.

13. There's a chemical element named after him.

Take a look at the periodic table of elements, and you might notice one with the symbol Cn. Called Copernicium, this element with atomic number 112 was named to honor the astronomer in 2010. The element is highly radioactive, with the most stable isotope having a half life of around 30 seconds.

14. Archaeologists finally discovered his remains in 2008.

Frombork Cathedral

Although Copernicus died in 1543 and was buried somewhere under the cathedral where he worked, archaeologists weren't sure of the exact location of his grave. They performed excavations in and around Frombork Cathedral, finally hitting pay dirt in 2005 by finding part of a skull and skeleton under the church's marble floor, near an altar. It took three years to complete forensic facial reconstruction and compare DNA from the astronomer's skeleton with hair from one of his books, but archeologists were able to confirm that they had found his skeleton. Members of the Polish clergy buried Copernicus for a second time at Frombork in 2010.


The Nicolaus Copernicus Monument in Warsaw, Poland.

A prominent statue of the astronomer, simply called the Nicolaus Copernicus Monument, stands near the Polish Academy of Sciences in Warsaw, Poland. There are also replicas of this monument outside Chicago's Adler Planetarium and Montreal's Planétarium Rio Tinto Alcan. Besides monuments, Copernicus also has a museum and research laboratory—Warsaw's Copernicus Science Centre—dedicated to him.

11 Spectacular Facts About the Moon

Matt Cardy/Stringer, Getty Images
Matt Cardy/Stringer, Getty Images

The Moon is Earth’s closest satellite in our solar system, but in many ways, we hardly know our neighbor. Scientists aren’t entirely sure how it formed, and other facts, like its shape (more egg-like than spherical), and the consistency of its surface (dusty but firm), were confirmed only recently. With the 50th anniversary of the Apollo 11 Moon landing this year, and NASA preparing to return to the lunar surface for the first time in decades, it’s time to brush up on these facts about the Moon—from colorful names for full moons to the first landing on the dark side of the Moon.

1. The Moon may have formed when a giant object in the solar system hit Earth.

Scientists aren't in total agreement on how the Moon formed, but the most widely accepted theory is the giant impact hypothesis. According to this theory, an object the size of Mars called Theia collided with Earth 4.5 billion years ago when the solar system was still new and chaotic. The impact dislodged matter from Earth’s crust, and the debris attached to whatever was left of Theia through the force of gravity.

This scenario would explain why the Moon is made up of lighter elements found in Earth’s outer layer, but it still leaves some questions unanswered. If the giant impact hypothesis is correct, about 60 percent of the Moon should consist of the impact object. Instead, its composition is almost identical to that of Earth. There are alternative explanations: one posits that the Moon is a space object that got caught in Earth’s orbit, and another one suggests the Moon and Earth formed at the same time, but none is as popular as the giant impact theory.

2. The Moon is the perfect size for solar eclipses.

Moon covering sun during solar eclipse.
Masashi Hara/Getty Images

A lucky set of circumstances make total solar eclipses, as seen from Earth, possible. The Moon is just the right size and distance from our planet to appear as the same size as the Sun in the sky. When the Moon passes between the Sun and the Earth, it covers the Sun perfectly with an impressive corona illuminating its edges. If it were any smaller or farther from Earth, it would look like a blot on the Sun during a solar eclipse.

3. A full Moon has different nicknames in different seasons.

A full moon can have many colorful names, but they don’t always describe a special celestial phenomenon. Some are used to refer to a full moon that appears during a certain time of year. A harvest moon, which is the full moon closest to the autumn equinox, is the best-known example, but there are many others, including a wolf moon (first full moon of January), strawberry moon (June), and sturgeon moon (August).

4. It’s the largest moon in the solar system relative to its planet.

Our Moon isn’t the largest in the solar system (that distinction goes to Ganymede, one of Jupiter’s 79 moons), but it is the biggest in relation to the planet it orbits. With a diameter of 2159 miles and a surface area of 14.6 million square miles, the Moon is a little more than one-fourth the size of Earth. The dwarf planet Pluto has an even smaller moon-to-planet ratio. Pluto’s largest moon Charon is nearly the size of its host body, leading some astronomers to refer to the pair as a double-dwarf planet.

5. The Moon is shaped like a lemon.

The Moon may look perfectly round in the night sky, but it’s actually more of an oval shape. It came out wonky billions of years ago when super-hot tidal forces shaped its crust, heating up some areas hotter than others to form a lemon shape rather than a perfect sphere. Gravitational forces from Earth have helped to exaggerate the Moon’s oblong appearance over eons.

6. Scientists thought Moon dust would cause lunar landers to sink.

Lunar module over moon's surface.

When preparing to send missions to the Moon, some scientists feared that a thick layer of dust on the body’s surface would cause complications. One of the strongest proponents of the dust theory was Thomas Gold, an astrophysicist at Cornell University. He insisted that the Moon was covered in seas of dust soft and thick enough to swallow a lunar lander. Though the Moon’s surface is dusty, the layer is too thin to cause problems, as the successful landings of the Soviet Luna 9 and the American Surveyor spacecrafts proved in 1966.

7. The Moon is international property.

Astronauts Buzz Aldrin and Neil Armstrong may have planted an American flag on the Moon in 1969, but it belongs to the world. Countries like the Soviet Union and the U.S. made sure of that at the height of the space race in 1967 when they signed the Outer Space Treaty, a document declaring that the Moon would be a “global commons” and any resources discovered there would be used for the good of the world overall. In keeping with the spirit of the agreement, NASA shared soil samples taken from the Moon with Soviet scientists upon the Apollo 11 mission's return.

8. Humans have left strange things on the Moon.

Since the first people landed on the Moon in 1969, its surface has been home to more than just dust. Earth artifacts left on the Moon by astronauts include two golf balls, an obscene Andy Warhol doodle, and a message from Queen Elizabeth II. Eugene Cernan, Apollo 17 commander and one of the last people to walk on the Moon, traced his daughter’s initials into the soil when he visited in 1972. Without any wind or weather on the Moon, the letters TDC could remain there forever.

9. The "dark side of the Moon" is the result of synchronous rotation.

Even though the Moon is constantly rotating, only one side of it is visible from Earth. This is because the Moon is locked in synchronous rotation. It takes the Moon just as long to complete one full rotation as it does for the body to orbit around the Earth once, so the same side always faces our planet. This isn’t a coincidence—the Earth’s gravitational forces have gradually pulled the tip of the slightly oblong Moon to point toward the planet, creating something called tidal lock.

In January 2019, the Chinese space agency landed the first lunar probe on the unexplored dark side of the Moon. The Chang'e 4 spacecraft sent the first photographs of a massive impact crater on the dark side to Earth, giving scientists their first glimpse of that unknown region.

10. One astronaut was allergic to the Moon.

Apollo 17 astronaut Harrison “Jack” Schmitt discovered the hard way that some people are allergic to Moon matter. Following a survey of a valley in the Sea of Serenity, he climbed back into the crew’s lunar module and tracked in a lot of Moon dust with him. The dust affected him as soon as he removed his spacesuit, triggering red eyes, sneezing fits, and other symptoms that lasted two hours.

11. Humans are going back to the Moon soon.

After completing several manned missions to the Moon, NASA ended the Apollo program in 1972 as budgets tightened and public interest waned. That means most people alive today have never witnessed a manned lunar landing, but now, following a hiatus nearing 50 years, NASA is finally preparing to return to the Moon. The next manned lunar expedition will be ready to launch “no later than the late 2020s,” according to the space agency. One of the goals will be placing a command module, called Gateway, in the Moon’s orbit that astronauts can reuse over multiple missions.