20 Top Experiments From 20 Years of Human Research on the International Space Station

Monday, November 2, 2020, marked 20 years since the first crew took up residence on the International Space Station. Since then the football field-sized feat of engineering has hosted 26 European missions and supported over 2700 international experiments to improve life on Earth and in space. Credit: ESA/NASA

As the world celebrates two decades of humans in orbit around Earth on the International Space Station, this month’s science summary will look back not at four weeks of European research in space, but 20 years – with a focus on human research, naturally.

In November 2000 the first human entered the two-module International Space Station and ESA ran its first experiment just three months later.

Expedition 1 crew in December 2000 about to eat oranges in the Zvezda module of the International Space Station. From left cosmonaut Yuri Gidzenko NASA astronaut William Shepherd and cosmonaut Sergei Krikalev. Expedition 1 was the first crew to live on the International Space Station. Credit: NASA

ESA’s human spaceflight research coordinator Jennifer Ngo-Anh explains the benefits of Space Station research, “We typically run three types of experiments, research that cannot be done on Earth, research to understand and improve astronaut health and research that exploits the unique aspect of sending perfectly healthy and fit humans into a new and stressful environment.”

“As you will see from the list below, this research is helping us explore farther into our Solar System, but it benefits people on Earth with new knowledge, new technology, and new techniques – spaceflight is a motor for ingenuity.”

This infographic shows some of the benefits for humankind that have been made available through ESA’s human and robotic spaceflight program. The challenges of space exploration accelerate innovation for all on Earth. Human and robotic spaceflight is moving technology towards a circular economy by improving efficiency in energy, automation, robotics, artificial intelligence, habitation technology, recycling, waste management, and additive manufacturing. Credit: ESA–K. Oldenberg

Here are 20 of ESA’s favorite experiments from two decades of habitation:

• Brain-DTI
  This study took brain scans of astronauts to measure ‘plasticity’ or how quickly their brains adapt to new inputs. The reassuring conclusion is that brains adapt surprisingly well, though research is hinting that the effects of floating in weightlessness mark the brain forever.

An MRI scan of a volunteer’s brain for the BRAIN-DTI experiment using tractography to show neural networks. Credit: B. Jeurissen

• 42 is the answer
  The Biolab facility in Columbus was used to investigate the time it takes for mammal immune cells to adapt to microgravity: 42 seconds, coincidentally the meaning of life according to Douglas Adams in The Hitchhiker’s Guide to the Galaxy and the number of the Space Station Expedition that performed the experiment!
• Circadian Rhythms
  This experiment monitors an astronaut’s body temperature to learn about our internal clock. A novel non-invasive thermometer was designed and marketed on Earth to get results that amazed researchers as it showed a sustained increase in body temperature.
• Endothelial cells
  Research into the cells that line our blood vessels is helping understand how and why they contract and expand, and why they have reduced functionality in old age on Earth.

Components of human endothelial cells stained for identification. In red is the ‘actin’ protein that allows the cells to move, adhere, divide, and react to stimuli. In blue are the cell nuclei containing DNA. Credit: Scuola Superiore Sant’Anna, Pisa, Italy

• Growing blood vessels
  Not content with just observing blood vessels, how about growing new ones in space? This experiment exploited weightlessness to see if we can grow new three-dimensional organs. On Earth, gravity pulls the cells down making 3D-structures harder to achieve in the lab.
• Better sleep
  Sleep is important, and being alert even more so if you are about to dock two spacecraft many millions of kilometers away from Earth. But how do you ensure astronauts get a good night sleep when the Sun sets 16 times a day seen from the International Space Station? Structure, light and chemical aids if necessary is the answer (so far), and these findings apply to you on Earth too.
• Vessel-ID
  This experiment is not research into humans, but it did literally save lives. The Vessel-ID global traffic monitoring receiver was tested outside the Columbus laboratory and picked up a distress beacon from a fishing ship; search and rescue authorities were then notified. What we learned from this experiment is now flying as a stand-alone satellite.
• Stressed immune systems
  The Immuno experiment took a holistic approach to investigating stress by utilizing questionnaires, blood samples and temperature readings from the astronauts showing that the immune system goes haywire. Through necessity, researchers developed new ways of analyzing small quantities of blood, so as not to drain the astronauts’ already-depleted supplies. Now, the hardware and the methods used are being shared with the medical community to aid the care of at-risk new-borns, who have even less blood to spare for analysis.
• Osteoporosis – salt ain’t good
  Astronaut bones go through accelerated osteoporosis during spaceflight. This disease costs Europe around €25 billion a year and typically affects the elderly, resulting in brittle and fragile bones and broken hips and arms from falls. Studying astronauts in space showed that acidity in the body accelerates bone loss, and you can counteract the acidity by eating less salt or taking bicarbonate pills as a simple preventive measure. On Earth a study would take decades to see results, but the accelerated aging seen in astronauts allows researchers to fast-track ideas.

ESA astronaut Frank De Winne installs experiment containers for the Yeast experiment in the Biolab incubator in Columbus on October 2, 2009. Credit: NASA

• 3D bone scanner
  To follow up on the above study in more detail, the EDOS-1 and 2 experiments required better medical scanners to see the finer structure of astronaut bones – so they created just that. The Xtreme CT scanner ESA helped develop can show the microscopic architecture of bones and their strength to monitor bones of everyone on and around Earth.
• Yeast
  Another experiment in Biolab investigated yeast strains that have been used to make bread and brew drinks for centuries. Unsurprisingly, in microgravity the yeast showed signs of stress and had problems building cell walls. The cells diverted their energy to repair themselves and grew less quickly. By analyzing the strains that performed better in microgravity, researchers could identify genes that could be used for longer space missions. Space-faring yeasts can be cultured for future missions to far-away planets – space bakery anyone?

• 5-LOX
  The 5-LOX enzyme regulates life expectancy of human cells. Most human cells divide and regenerate, but the number of times they replicate is limited. Italian researchers wanted to find out how this enzyme was affecting astronauts’ health in space and found that cells flown in space showed more 5-LOX activity than the centrifuged samples, giving scientists a target enzyme that could play a role in the weakening of immune systems. The enzyme can be blocked with existing drugs, so using these findings to improve human health is a close reality. Who knows what life-prolonging pills could be developed in the future, all thanks to a two-day space experiment.
• Finding the key
  A similar experiment put immune cells through artificial gravity in space and showed that a specific transmitter in the cells, called the Rel/NF-kB pathway, stops working in weightlessness. Finding which gene does what is like looking for the right key to fit a keyhole, without having found the keyhole yet. Studying cells that have flown on the International Space Station is putting researchers on the right path to finding the key to how our immune system works. The pharmaceutical industry could also find the genes that need to be active to fight specific illnesses and market tailored antibodies.
• Laser eyes
  Where do astronauts look in space? A simple question for science, but to answer it the research team behind this experiment needed to track the astronauts’ eyes at all times. New hardware was developed for this space research and it is now found in almost all laser-eye surgeries in Europe where surgical precision is key.

Cosmonaut Sergei Krikalev wearing ESA’s Eye Tracking Device during Expedition 11 to the International Space Station in 2005. Credit: ESA/NASA

• Remote diagnosis
  Keeping an astronaut fit and healthy from a distance is the flight surgeon’s task on Earth. Not all astronauts can be medical doctors, so small, easy-to-use machines are required for diagnosis but also for research into human health. Great strides have been made over the last two decades in ultrasound machines, heart-rate monitors, thermometers as well as in operating and sending the data to medical professionals many thousands of kilometers away. The Tempus Pro machine is the culmination of this and can be used equally effectively all over our planet.
• Stay strong
  Strong muscles are hard work on Earth – and even harder in space where certain muscles used to walk or sit are not needed in weightlessness, the “antigravity muscles”. Studies have shown that astronauts experience up to a 20% loss of muscle mass in short-duration missions alone, which is worrying for an astronaut about to land on Mars after a nine-month flight. The Muscle Biopsy experiment is investigating how cells communicate (called signaling pathways). Researchers suspect cell communication is tied to gravity-sensing and that the cells communicate less in space. The study is still in progress but the science team already have images from muscle biopsies that show enlarged intramuscular tissue spaces after a flight, an initial confirmation of their hypothesis.
• Lung health
  How do lungs adapt to spaceflight? This Swedish-led study put astronauts in the Space Station’s airlock and pumped out air to reduce the pressure, showing surprising results in the nitric oxide levels exhaled. Researchers developed a drug with a uniquely selective effect in lung circulation. The drug widens the blood vessels and counteracts life-threatening increases of local blood pressure. On the Moon and Mars, astronauts’ lungs may become easily irritated or inflamed by dust particles as they don’t settle to the ground but circulate endlessly.

ESA astronaut Samantha Cristoforetti on the International Space Station working with equipment for the Airway Monitoring investigation. Credit: ESA/NASA

• Old age
  Our brains change all the time – nerves and connecting cells rearrange to every new experience, but become less good at it in old age. Scientists peered inside astronauts’ heads for the Neurospat experiment to understand how they adapt to their new environments and developed new tools for testing spatial cognition that will be of great help to our aging brains.
• Humans are cleaner than we thought
  For twenty years humans have been living in the closed International Space Station – without a shower to wash in. There is no place on Earth where researchers can investigate how bacteria evolve and live in such a tight-knit environment. Concern about rampant bacteria growth is always here, but it turns out that it is not that bad, with around 55 types of bacteria finding healthy equilibrium around the Space Station. This doesn’t mean that research is being done into easy-clean materials that will keep bacteria in check.
• Mix it up
  This series of experiments is physics-based, but looking at how liquids mix on a molecular level is improving shelf-life of medicine on Earth. The SODI experiments in essence observe two liquids together in weightlessness. As the two liquids constantly mingle and interfere with each other, the results are interesting for companies developing anti-body-based medicine that is notoriously known to be unstable liquids.

This is just a small selection of the European experiments run on the International Space Station that focus on human research. Around 400 ESA investigations have been performed since the first module was launched and thousands more are led by the four other space agencies that work together to keep the Space Station aloft: NASA, Russia’s Roscosmos, Japan’s JAXA, and the Canadian Space Agency.

This panorama of the International Space Station is a wider view of what ESA astronaut Luca Parmitano was capturing on camera during the first of a series of historic spacewalks that took place in November 2019. Author, journalist and researcher Lee Brandon-Cremer created this photo by stitching together three images taken by Luca as he made his way to the worksite during the first Extravehicular Activity or EVA to service the Alpha Magnetic Spectrometer (AMS), the Station’s dark matter detector. Credit: L. Brandon-Cremer

With the Space Station set to continue running for many more years, the future is bright for research in our unique laboratory. “We listened to researchers and companies and are making space research more accessible, for example with companies offering services to design, build, fly and run experiments in one package deal,” says Jennifer.

“Research run on the Space Station almost always delivers surprising results, advancing our knowledge of the world, humankind and benefiting people on Earth. For 20 years we have been working on the forefront of where science and engineering meet, and I am looking forward to seeing many more years of interesting experiments and results.”