High above our heads, at an altitude of about 400 kilometers, the International Space Station (ISS) constantly orbits the Earth at a speed of nearly 28,000 kilometers per hour. It is much more than just a human outpost in orbit; it is the most extraordinary and productive scientific laboratory humanity has ever built. Its exceptional value rests on three fundamental pillars: a persistent microgravity environment that defies the laws of physics as we know them on Earth, a unique orbital path that provides an unparalleled view of our planet and the infinite universe, and, most importantly, the indispensable role of its human crew. The astronauts are not just passengers; they are scientists, engineers, and, often, the subjects of research themselves in this high-tech laboratory that pushes the boundaries of human knowledge and technological advancement.

A Laboratory Beyond the Reach of Gravity: Reshaping Fundamental Sciences

One of the key advantages of the International Space Station is its long-term, stable access to microgravity. The removal of the dominant influence of Earth's gravity transforms the way fundamental physical, chemical, and biological processes occur, opening up entirely new horizons in numerous scientific disciplines. In this weightless environment, scientists can isolate and study phenomena that are masked or distorted by gravity on Earth, leading to revolutionary discoveries.

The Physics of a Weightless World: From Spherical Flames to Perfect Alloys

In microgravity conditions, fundamental phenomena like combustion behave in completely unexpected ways. On Earth, hot air rises, creating convection currents that give flames their characteristic teardrop shape. On the ISS, without this buoyant force, flames take on an almost perfect spherical shape. But the changes are deeper than just geometry. A series of experiments, such as Burning and Suppression of Solids (BASS) and the large-scale Saffire tests conducted on unmanned Cygnus spacecraft after undocking from the station, have revealed fascinating and crucial details. Scientists discovered the existence of "cool flames" that burn at lower temperatures and can be invisible to the human eye, posing a significant risk. These studies, which examined the combustion of various materials, showed that fire in space spreads more slowly and in different ways. Understanding these processes is vital for developing advanced fire detection and suppression systems, crucial for the safety of future long-duration missions to the Moon and Mars.

Similarly, microgravity opens up new possibilities in materials science. In the Materials Science Research Rack (MSRR) module, scientists study how metals, alloys, and semiconductors behave without gravity-induced convection and sedimentation. When alloys cool from a molten state on Earth, heavier elements sink and lighter ones rise, leading to an inhomogeneous structure. In space, this process is eliminated, allowing for the creation of more perfect and uniform crystal structures. This knowledge helps in developing lighter, stronger, and more durable alloys on Earth, as well as in producing purer semiconductor crystals for advanced electronics. The ability to process materials "levitating," without contact with container walls, allows for more precise measurements of their fundamental properties, such as viscosity and surface tension, which is nearly impossible to achieve on Earth.

However, science on the ISS has also revealed a fascinating paradox. While microgravity is the primary tool for many experiments, the station itself is not a perfectly still environment. Constant vibrations from the operation of life support systems, fans, and even the movement of astronauts during exercise can interfere with the most sensitive experiments. This has led to the development of incredibly sophisticated technology, such as the Controlled Dynamics Locker (CDL). This device uses magnetic forces to levitate an experimental sample within a chamber, effectively isolating it from the vibrations of the station itself. In this way, scientists create a "cleaner" microgravity environment within the existing one. This demonstrates how complex and challenging it is to conduct precise science in orbit, where microgravity is simultaneously a powerful tool and a variable that needs to be constantly controlled and filtered.

A Blueprint for Life Sciences: Protein Crystallization and a Pharmaceutical Revolution

One of the most fruitful areas of research on the ISS, directly impacting human health on Earth, is Protein Crystal Growth (PCG). Proteins are the fundamental building blocks of life and are crucial for almost all biological processes. To understand a protein's function and develop a drug that targets it specifically, scientists need to know its precise three-dimensional structure. The best way to do this is through X-ray diffraction analysis, which requires large and nearly perfect protein crystals.

On Earth, gravity is a major obstacle. It causes sedimentation and convection currents in the solution from which crystals grow, resulting in smaller, imperfect, and often unusable crystals. In the microgravity of the ISS, these disruptive factors are minimized. This allows for the growth of significantly larger and structurally more uniform crystals. These high-quality samples, when returned to Earth and analyzed, provide scientists with a high-resolution 3D map of the protein, revealing the position of every single atom. In modern pharmacology, many diseases are linked to malfunctioning proteins. Understanding their structure is like having a precise blueprint of the "lock" that needs to be unlocked. With this blueprint, chemists can design a molecular "key"—a drug that will bind perfectly to the target protein, blocking its harmful activity with maximum efficiency and minimal side effects. It is not surprising that PCG, with hundreds of studies conducted, is the largest single category of experiments on the station, attracting interest from leading pharmaceutical companies and academic institutions worldwide.

The Human Factor: Adapting to the Final Frontier and Solving Its Riddles

While physics and biology are key, the most complex and important subject of research on the International Space Station is the human body itself. Astronauts are not just scientists conducting experiments; they are the experiment. Their bodies become living laboratories for studying the profound physiological and psychological changes that occur during long-duration spaceflight. Understanding and solving these challenges is not just an academic exercise—it is a critical prerequisite for the future of human space exploration, including planned missions to Mars.

The SANS Enigma: A Mystery Threatening the Journey to Mars

One of the most serious medical challenges that has emerged with long-duration missions on the ISS is a condition known as Spaceflight Associated Neuro-ocular Syndrome (SANS). First noticed when astronauts began spending months in orbit, SANS affects about 70% of crew members on long missions. Symptoms include changes in vision, most commonly the development of farsightedness (a hyperopic shift), swelling of the optic disc, choroidal and retinal folds in the back of the eye, and a slight flattening of the eyeball. Although no astronaut has yet experienced permanent and significant vision loss, some of the effects, such as retinal folds, can persist even after returning to Earth.

The leading hypothesis, investigated by the Fluid Shifts experiment, is that in microgravity, a redistribution of bodily fluids occurs. On Earth, gravity pulls blood and other fluids toward the legs. In space, this fluid shifts toward the upper body and head, potentially increasing intracranial pressure and exerting pressure on the back of the eye, changing its shape and affecting vision. SANS represents one of the greatest health risks for future deep space missions. The condition is "dose-dependent"—the longer the stay in space, the greater the risk and potential severity of the symptoms. Given that a round-trip mission to Mars could last up to two and a half years, the long-term effects that SANS could have on crew health are unknown. That is why NASA, in collaboration with institutions like Houston Methodist, is investing enormous effort in understanding, monitoring, and preventing this syndrome. Various countermeasures are being developed and tested, including wearing venoconstrictive cuffs on the thighs to keep fluid in the lower body, and using a Lower Body Negative Pressure (LBNP) device, which acts like a vacuum cleaner and pulls fluids back toward the legs, simulating the effect of gravity. For future Mars missions, where a communication delay of about 20 minutes one-way prevents real-time consultations, portable diagnostic devices and AI-based systems are also being developed to allow astronauts to independently monitor their eye health.

This intense focus on SANS and other human factors reveals the unique nature of the ISS. Unlike robotic probes, whose science is separate from the instrument itself, on the station, science is inextricably linked to the human presence. The challenges of sustaining human life and health in the hostile environment of space have become one of the most fruitful fields of research. The mission of exploration itself has become a profound scientific endeavor. The ISS is not just a place where science is conducted; it is a place where the science of what it means to be human in space is being written.

Hacking the Body Clock: How to Beat 16 Sunrises a Day

One of the more subtle, but extremely important, challenges for astronauts is the disruption of their biological clock. Orbiting the Earth every 90 minutes, the crew experiences 16 sunrises and sunsets each day. This unnatural cycle of light and dark disrupts their internal, 24-hour circadian rhythm, leading to sleep problems, fatigue, and reduced productivity. Studies have shown that astronauts often sleep less than recommended, relying on sleeping pills and caffeine to keep up with their demanding schedules.

To solve this problem, scientists devised the Lighting Effects study. As part of this long-term research, conducted from 2016 to 2020, the old fluorescent bulbs on the station were replaced with an advanced LED system (Solid-State Light Assemblies - SSLA) with adjustable intensity and color spectrum. The system uses three main settings: general lighting for normal work during the day; a setting with enhanced blue light for the morning hours, which promotes alertness and helps to "reset" the body clock; and a "pre-sleep" setting with low intensity and a reduced amount of blue light. Blue light inhibits the production of melatonin, the sleep hormone, so removing it before sleep helps the brain to calm down and prepare for rest. The results showed that dynamic lighting can significantly improve the crew's sleep, mood, and cognitive performance. This technology, perfected in space, has enormous potential on Earth, where it can be used to help shift workers, treat sleep disorders, and mitigate the effects of jet lag.

Lunch on the Way to Mars: From Space Radishes to Microbe-Based Protein

Ensuring a nutritious and sustainable diet is crucial for future long-duration missions. On the way to Mars, which could take months or years, there will be no opportunities for resupply from Earth. Therefore, growing fresh food in space is one of the research priorities on the ISS. In a series of experiments, astronauts have successfully grown various types of plants, including lettuce, kale, and chili peppers. One of the most famous examples is the cultivation of radishes, which the crew not only grew but also ate, describing their taste as "just as good as from their own garden."

These experiments are not just gardening in space; they are key to understanding how plants grow in microgravity and how to optimize conditions for maximum yield. But NASA is looking beyond traditional agriculture. Through the Deep Space Food Challenge initiative, the agency is encouraging the development of revolutionary food production technologies. Among the most interesting ideas are systems that use edible microbes that feed on carbon dioxide, hydrogen, and oxygen to create protein. Another promising option is fungi, or mycoproteins derived from them, which can be shaped into different textures and flavors, from pasta to meat substitutes. These innovations could provide a sustainable, nutritious, and tasty food source for the first human explorers of the Red Planet.

A Guardian's View: Monitoring Earth and Its Fragile Systems

The unique orbital path of the International Space Station provides an extraordinary platform for observing our planet. Unlike most Earth-observation satellites, which are in sun-synchronous polar orbits and pass over the same point at the same local time each day, the ISS has an inclined orbit of 51.6 degrees. This means it flies over 90% of the Earth's populated surface at different times of the day and night, under different lighting angles. This variability is invaluable for scientists studying dynamic processes on Earth, such as the development of coastal fogs, the daily cycle of plant growth, or urban sprawl.

This ability to observe at different times makes the ISS a key tool for monitoring and responding to natural disasters. Instruments like ISERV, as well as astronauts with handheld cameras, can capture high-resolution images of flooded areas, wildfires, landslides, or the aftermath of earthquakes, often just hours after the event. This information is quickly relayed to emergency response teams on the ground, helping them to assess damage and direct rescue efforts. One of the most famous examples is the footage of the Sarychev volcano eruption in the Kuril Islands, which astronauts recorded in real time, providing a unique insight into the dynamics of volcanic eruptions. In the long term, data from the ISS is crucial for monitoring climate change, including glacier melt, deforestation, and changes in agricultural land, giving us a comprehensive picture of our planet's health.

This dual role reveals another fascinating dimension of the station's scientific mission. It operates simultaneously on two completely different timescales. On one hand, it is a rapid-response platform, providing data crucial for resolving urgent, terrestrial crises within hours. On the other, it is a patient, long-term observatory addressing eternal questions about the nature of the universe and human adaptation, the full significance of which may only be realized in several decades. This duality makes its scientific portfolio incredibly robust and justifies its complexity from both a practical and a visionary perspective.

Unlocking Cosmic Secrets: The Hunt for Dark Matter Above the Atmosphere

While looking toward Earth with one eye, the ISS is focused with the other on the deepest mysteries of the universe. Mounted on its external structure is one of the most sophisticated particle physics instruments ever sent into space—the Alpha Magnetic Spectrometer (AMS-02). This powerful, seven-ton particle detector constantly analyzes cosmic rays—high-energy particles that travel through space at nearly the speed of light. Its main goal is the search for evidence of dark matter and antimatter, the two most enigmatic components of our universe.

Since its installation, AMS-02 has detected hundreds of billions of cosmic rays and made a stunning discovery. It found an unexpected excess of positrons, the antimatter counterparts of electrons, in a specific energy range. According to existing theories, the proportion of positrons in cosmic rays should decrease as energy increases, but AMS showed the opposite—their proportion is growing. More importantly, recent data has shown that this increase does not continue indefinitely. At an energy of about 275 billion electron-volts, the positron fraction begins to drop sharply. This "turning point" is a key clue. Scientists have two main hypotheses: the excess of positrons could be a byproduct of the annihilation of dark matter particles, the invisible substance that makes up about 27% of the universe. Alternatively, they could originate from known astronomical sources, such as rapidly rotating neutron stars known as pulsars. The way the positron fraction decreases after the turning point will provide crucial information to distinguish between these theories. With the collection of additional data, AMS-02 is bringing us closer to answering one of the fundamental questions about the composition of our universe.

The Orbital Dividend: How Space Research Changes Life on Earth

Although the science on the ISS often seems distant and abstract, its results have a profound and real impact on everyday life on Earth. Innovations developed to solve the unique challenges of living in space often find application in unexpected areas, creating what is known as the "orbital dividend" or spinoff technologies.

A New Era in Drug Development: From Muscular Dystrophy to Cancer Treatment

Perhaps the most direct and powerful impact of ISS research is seen in medicine, particularly in the development of new drugs. Returning to protein crystallization, the theoretical advantage of growing perfect crystals in space has been translated into concrete results. One of the most prominent examples is research related to Duchenne muscular dystrophy (DMD), a severe and incurable genetic disease. By analyzing high-quality crystals of a protein associated with DMD, grown on the station, Japanese scientists were able to design a candidate drug, known as TAS-205. It is estimated that this drug could slow the progression of the disease by half, significantly improving the quality and length of life for patients. The drug has gone through clinical trials, showing how fundamental space science can lead to revolutionary therapies.

Another example is the work on the cancer drug Keytruda®, which is used to treat melanoma and other types of cancer. This drug is typically administered via a lengthy intravenous infusion in a hospital setting. Research on the ISS is focused on creating a more stable and uniform crystalline suspension of the drug. Success in this would allow the drug to be administered via a simple subcutaneous injection, which would drastically improve patient comfort and quality of life, reduce time spent in the hospital, and lower treatment costs. In addition, research on the station has contributed to identifying target structures for drugs against tuberculosis, breast cancer, and gum disease, confirming that the ISS has become a key platform for pharmaceutical innovation.

The Spinoff Effect: Technologies That Came Down to Earth

The challenges of living in a closed system like the ISS, where every resource must be maximally utilized and recycled, act as a powerful engine for innovation. The need to recycle every drop of water, including wastewater and sweat, has led to the development of extremely advanced water purification systems. This same technology is used on Earth today in portable filtration systems that provide clean drinking water in areas affected by natural disasters or in remote communities without access to clean water.

Many other technologies that we take for granted have their roots in space research. Memory foam, now ubiquitous in mattresses, pillows, and medical devices, was originally developed by NASA to improve the safety and comfort of spacecraft seats and absorb energy upon impact. Cordless tools, freeze-dried food that preserves nutritional value, and advanced insulation materials are just some examples of technologies that have made their way from orbit into our homes. These examples show that investments in space research are, in fact, investments in a better future on Earth. The constraints of the space environment force us to develop hyper-efficient, reliable, and sustainable solutions, turning the ISS not only into a laboratory for observing the universe but also into an incubator for technologies that will shape sustainable life on our planet.

Source: nasa.gov