12 Cool Experiments Done on the International Space Station


As an orbiting laboratory, the International Space Station (ISS) offers researchers around the world the unique opportunity to perform experiments in microgravity and under the rigors of the space environment. Scientists have used the station for everything from testing technology for future space exploration to studying human health. Sometimes their work involves some pretty unusual experiments. Here are 12 cool ones. 

1. Headless flatworms

On Earth, flatworms can regenerate their own cells, replacing them as they age or are damaged. Scientists cut the heads or tails off of flatworms and sent them to the station in September 2014 to study whether the cell signaling mechanisms behind this regeneration work the same way in space as they do on Earth.  The results should provide insight into how gravity affects tissue regeneration and the rebuilding of damaged organs and nerves, which is important for understanding how wounds heal—both in space and on the ground.

2. Space mice

For humans to explore deep space or live on other planets, we must learn how to deal with the effects of long-term exposure to potent space radiation, which can cause cancer and gene mutations, affecting subsequent generations. Lab mice are important tools for studying radiation effects, but currently, mice can’t go to the station. So instead, this investigation will send frozen mouse embryos for a ride in space and implant them into surrogate mothers on their return to Earth. Scientists will use these space mice to study longevity, cancer development, and gene mutations.

3. Talking Zucchini

In 2012, Astronaut Don Pettit wrote blog posts on behalf of a zucchini plant that was grown from a seed on the space station, one of many investigations on growing greenery in space. The ultimate goal is using plants to provide oxygen and fresh produce for crews on long-term space missions. Gravity plays an important role in normal plant growth and development, though, and not only is gravity nearly nonexistent in space, but plants also are affected by radiation, changes in light, and other factors of the space environment. The anthropomorphic Zucchini and its blog were a way to engage students with space-based research and encourage the next generation of space station scientists.

4. Putting out the fire

Fire behaves differently in space, thanks to complicated interactions of fuel vaporization, radiative heat loss, and chemical kinetics. Effectively extinguishing flames in space depends on understanding those interactions. This investigation, performed earlier this month, tested various fire suppressants in microgravity. Researchers found that flames in space burn with a lower temperature, at a slower rate, and with less oxygen than in normal gravity, meaning higher concentrations of materials must be used to put them out. The most surprising discovery was the way heptane droplets seemed to continue to burn under certain conditions even after the initial fire was extinguished. This phenomenon is called "cool-flame extinction." Those who understand conventional theories of droplet combustion say those theories don’t explain this behavior, making the cool flames a unique observation with significant theoretical and practical implications.

5. ISS, Robot

This two-armed humanoid robot torso mounted in the station can manipulate hardware and work in high risk environments to give crewmembers a break. Robonaut is operated via remote control and can be directed by ground operators through cabin video and telemetry. The half-a-mechanical astronaut also can be controlled by a crewmember wearing a vest, specialized gloves, and a 3D visor. Through this technology, Robonaut mimics the wearer’s movements in Wii-like fashion. In the future, the torso will be given legs and used to perform tasks both inside and outside the ISS.

6. Night lights—Lots of them

The publicly-accessible, online Gateway to Astronaut Photography of Earth contains photographs from space beginning with the early 1960s up to recent days. A million-plus of these images were taken from the space station, approximately 30 percent of them at night. These photographs are the highest-resolution night imagery available from orbit, thanks to a motorized tripod that compensates for the station’s speed—approximately 17,500 mph—and the motion of the Earth below. Scientists are asking for help cataloging the images through a crowd-source project called Cities at Night. It includes three components: Dark Skies of ISS, which asks people to sort images into cities, stars, and other categories (something computers aren’t good at); Night Cities, which relies on people to match the images to positions on maps; and Lost at Night, which seeks to identify cities within 310-mile-diameter images. Ultimately, the data generated could help save energy, contribute to better human health and safety, and improve our understanding of atmospheric chemistry.

7. Channeling Captain Kirk

Famous explorers kept journals that give us insight into what it took to survive extreme missions, such as reaching the South Pole. Spending months confined in cramped quarters orbiting the earth is one of today’s extreme missions, and for this study, researchers asked 10 crew members aboard the station to keep journals. Crew members wrote on a laptop at least three times a week, and investigators identified 24 major categories of entries with behavioral implications. Ten of those categories accounted for 88 percent of the text: work, outside communications, adjustment, group interaction, recreation/leisure, equipment, events, organization/management, sleep, and food. Men and women from various specialties such as science and engineering and both military and civilians participated. Studying small groups living and working in isolation and confinement is like studying social issues with a microscope, scientists say.

8. The Force is strong here

This project evaluated funky footwear designed to measure exercise load. NASA developed the Advanced Resistive Exercise Device, which supplies resistance through the power of vacuum cylinders, to give crew members the ability to do weight-bearing exercise in space. Weight-bearing exercise is critical to helping reduce the loss of bone density and skeletal muscle strength that astronauts experience during spaceflight. Four crew members exercised while wearing the high-tech, spring-bottomed sandals, which, like a kind of enhanced bathroom scale, measured the loads and the torque, or twisting force, they applied. The data will help determine the best exercise regimens for safe and effective bone and muscle strength maintenance during spaceflight.

9. Squids in space.

Hawaiian bobtail squids and their symbiotic luminescent bacterium take a ride to the space station. Rather than the start of a joke, this was part of an experiment, performed in September, to look at the effect of microgravity on microbe-dependent animal development and its implications for human health. The squid were inoculated with their symbiotic bacteria once in orbit on the space station and allowed to develop for approximately 24 hours. Researchers closely examined them and found that the bacteria were able to colonize squid tissue in microgravity conditions. The experiment also illustrated the feasibility of using these animals as subjects for microgravity research, so expect to see more squid in space in the future.

10. My microbes grow better than your microbes

For this project, people collected swabs of micro-organisms from museums, historical monuments, football stadiums, and weird places like Sue the T. Rex at Chicago’s Field Museum, the set of the Today Show, and the Liberty Bell. Scientists at University of California - Davis transferred those samples to Petri dishes, incubated them to see which grew into colonies, and identified 48 to send to the space station. Scientists need to know how various microbes behave in space before we seal up people and their microbes in a spacecraft for a long trip together to Mars. The 48 samples and identical cultures on Earth will be analyzed to see how their growth differs between microgravity and the ground. Each microbe has an online trading card that tells where it was collected, how well it grows, and some interesting facts about it.

11. Sloshing around the station

In space, liquids move differently than they do on earth, but the physics of this motion are not well understood. Researchers at the Florida Institute of Technology, Massachusetts Institute of Technology and NASA’s Kennedy Space Center performed a series of experiments on slosh dynamics in the station using robotic, free-floating satellites that can independently navigate and re-orient themselves. Researchers hope to design an externally mounted fuel tank that is driven from inside the station by two of these devices to simulate a launch vehicle upper-stage propellant tank and the maneuvers of real vehicles. The experiments will improve computer models of how liquid fuel behaves to make rockets safer.

12. Ant Farm

This investigation compared the behavior of groups of ants in normal gravity and in microgravity and measured how interactions among ants depend on the number of ants in a given area. Eight ant habitats with approximately 100 residents each launched to the space station, where scientists used cameras and software to analyze their movement patterns and interaction rates. Ant colony behavior is a combination of responses by individual ants to local cues, and previous studies suggest ants use the rate at which an individual meets other ants to determine how many of them are in the area. This estimation of group density is needed in many different situations, such as searching for food. When there are many ants in a small space, each ant moves round and round in roughly the same place, but when density is low, each ant walks a straighter path to cover more ground. Data on the ant colony’s adaptations can be used to build various algorithms, or sets of steps followed in order to solve a mathematical problem. For example, ant-based algorithms could help scientists develop cheaper, more efficient strategies for robot-based searching and exploration.

Vivien Killilea/Getty Images for Caruso Affiliated
A Founder of Earth Day Looks Back on How It Began
Vivien Killilea/Getty Images for Caruso Affiliated
Vivien Killilea/Getty Images for Caruso Affiliated

On the very first Earth Day in 1970, Denis Hayes stood on a stage in Central Park, stunned by the number of people who'd come to honor the planet. Now in his 70s, Hayes remembers it was like looking at the ocean—“you couldn’t see where the sea of people ended.” Crowd estimates reached more than a million people.

For Hayes, who is now board chair of the international Earth Day Network, it was the culmination of a year’s worth of work. As an urban ecology graduate student at Harvard University, he’d volunteered to help organize a small initiative by Wisconsin senator Gaylord Nelson. Nelson was horrified by the 1969 oil spill in Santa Barbara, California, and wanted to raise awareness about environmental issues by holding teaching events similar to those being held by civil rights and anti-war activists.

Senator Nelson saw a growing disconnect between the concept of progress and the idea of American well-being, Hayes tells Mental Floss. “There was a sense that America was prosperous and getting better, but at the same time, the air in the country was similar to the air today in China, Mexico City, or New Delhi," Hayes says. "Rivers were catching on fire. Lakes were unswimmable.”

Nelson's plan for these environmental teach-ins was for speakers to educate college students about environmental issues. But he had no one to organize them. So Hayes, Nelson’s sole volunteer, took control on a national level, organizing teach-ins at Harvard first and then across the U.S. Initially, the response was tepid at best. “Rather rapidly it became clear that this wasn’t a hot issue at colleges and universities in 1969,” Hayes says. “We had a war raging, and civil rights were getting very emotional after the Nixon election.”

Still, both Hayes and Nelson noticed an influx of mail to the senator's office from women with young families worried about the environment. So instead of focusing on colleges, the two decided to take a different tactic, creating events with community-based organizations across the country, Hayes says. They also decided that rather than a series of teach-ins, they'd hold a single, nationwide teach-in on the same day. They called it Earth Day, and set a date: April 22.

Hayes now had a team of young adults working for the cause, and he himself had dropped out of school to tackle it full time. Long before social media, the project began to spread virally. “It just resonated,” he says. Women and smaller environmental-advocacy groups really hooked onto the idea, and word spread by mouth and by information passing between members of the groups.

Courtesy of Denis Hayes

With the cooperation and participation of grassroots groups and volunteers across the country, and a few lawmakers who supported the initiative, Hayes’ efforts culminated in the event on April 22, 1970.

Hayes started the day in Washington, D.C., where he and the staff were based. There was a rally and protest on the National Mall, though by that point Hayes had flown to New York, where Mayor John Lindsay provided a stage in Central Park. Parts of Fifth Avenue were shut down for the events, which included Earth-oriented celebrations, protests, and speeches by celebrities. Some of those attending the event even attacked nearby cars for causing pollution. After the rally, Hayes flew to Chicago for a smaller event.

“We had a sense that it was going to be big, but when the day actually dawned, the crowds were so much bigger than anyone had experienced before,” Hayes said. The event drew grassroots activists working on a variety of issues—Agent Orange, lead paint in poor urban neighborhoods, saving the whales—and fostered a sense of unity among them.

“There were people worrying about these [environmental] issues before Earth Day, but they didn’t think they had anything in common with one another," Hayes says. "We took all those individual strands and wove them together into the fabric of modern environmentalism.”

Hayes and his team spent the summer getting tear-gassed at protests against the American invasion of Cambodia, which President Nixon authorized just six days after Earth Day. But by fall, the team refocused on environmental issues—and elections. They targeted a “dirty dozen” members of Congress up for re-election who had terrible environmental records, and campaigned for candidates who championed environmental causes to run against them. They defeated seven out of 12.

“It was a very poorly funded but high-energy campaign,” Hayes says. “That sent the message to Congress that it wasn’t just a bunch of people out frolicking in the sunshine planting daisies and picking up litter. This actually had political chops.”

The early '70s became a golden age for environmental issues; momentum from the Earth Day movement spawned the creation of the Clean Air Act, the Clean Water Act, the Safe Drinking Water Act, the Endangered Species Act, the Marine Mammal Protection Act, the Environmental Education Act (which was initially passed in 1970 and revived in 1990), and the Environmental Protection Agency.

“We completely changed the framework within which America does business, more than any other period in history with the possible exception of the New Deal,” Hayes says. “But our little revolution was brought entirely from the grassroots up.”

In 1990, Hayes was at it again. He organized the first international Earth Day, with about 200 million participants across more than 140 countries. Since then it’s become a global phenomenon.

Despite its popularity, though, we still have a long way to go, even if the improvements Hayes fought for have made these issues feel more remote. Hayes noted that everything they were fighting in the '70s was something tangible—something you could see, taste, smell, or touch. Climate change can seem much less real—and harder to combat—to the average person who isn’t yet faced with its effects.

Hayes also notes that people have become more skeptical of science. “Historically, that has not been a problem in the United States. But today science is under attack.”

He warns, “This [anti-science sentiment] is something that could impoverish the next 50 generations and create really long-term devastation—that harms not only American health, but also American business, American labor, and American prospects.”

Scott Butner, Flickr // CC BY-NC-ND 2.0
Look Up! The Lyrid Meteor Shower Arrives Saturday Night
Scott Butner, Flickr // CC BY-NC-ND 2.0
Scott Butner, Flickr // CC BY-NC-ND 2.0

There is a thin line between Saturday night and Sunday morning, but this weekend, look up and you might see several of them. Between 11:59 p.m. on April 21 and dawn on Sunday, April 22, the Lyrid meteor shower will peak over the Northern Hemisphere. Make some time for the celestial show and you'll see a shooting star streaking across the night sky every few minutes. Here is everything you need to know.


Every 415.5 years, the comet Thatcher circles the Sun in a highly eccentric orbit shaped almost like a cat's eye. At its farthest from the Sun, it's billions of miles from Pluto; at its nearest, it swings between the Earth and Mars. (The last time it was near the Earth was in 1861, and it won't be that close again until 2280.) That's quite a journey, and more pressingly, quite a variation in temperature. The closer it gets to the Sun, the more debris it sheds. That debris is what you're seeing when you see a meteor shower: dust-sized particles slamming into the Earth's atmosphere at tens of thousands of miles per hour. In a competition between the two, the Earth is going to win, and "shooting stars" are the result of energy released as the particles are vaporized.

The comet was spotted on April 4, 1861 by A.E. Thatcher, an amateur skywatcher in New York City, earning him kudos from the noted astronomer Sir John Herschel. Clues to the comet's discovery are in its astronomical designation, C/1861 G1. The "C" means it's a long-period comet with an orbit of more than 200 years; "G" stands for the first half of April, and the "1" indicates it was the first comet discovered in that timeframe.

Sightings of the Lyrid meteor shower—named after Lyra, the constellation it appears to originate from—are much older; the first record dates to 7th-century BCE China.


Saturday night marks a first quarter Moon (visually half the Moon), which by midnight will have set below the horizon, so it won't wash out the night sky. That's great news—you can expect to see 20 meteors per hour. You're going to need to get away from local light pollution and find truly dark skies, and to completely avoid smartphones, flashlights, car headlights, or dome lights. The goal is to let your eyes adjust totally to the darkness: Find your viewing area, lay out your blanket, lay down, look up, and wait. In an hour, you'll be able to see the night sky with great—and if you've never done this before, surprising—clarity. Don't touch the smartphone or you'll undo all your hard ocular work.

Where is the nearest dark sky to where you live? You can find out on the Dark Site Finder map. And because the shower peaks on a Saturday night, your local astronomy club is very likely going to have an event to celebrate the Lyrids. Looking for a local club? Sky & Telescope has you covered.


You don't need a telescope to see a meteor shower, but if you bring one, aim it south to find Jupiter. It's the bright, unblinking spot in the sky. With a telescope, you should be able to make out its stripes. Those five stars surrounding it are the constellation Libra. You'll notice also four tiny points of light nearby. Those are the Galilean moons: Io, Europa, Ganymede, and Callisto. When Galileo discovered those moons in 1610, he was able to prove the Copernican model of heliocentricity: that the Earth goes around the Sun.


First: Don't panic. The shower peaks on the early morning of the 22nd. But it doesn't end that day. You can try again on the 23rd and 24th, though the numbers of meteors will likely diminish. The Lyrids will be back next year, and the year after, and so on. But if you are eager for another show, on May 6, the Eta Aquariids will be at their strongest. The night sky always delivers.


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