This November marks an extremely important jubilee in the history of human space exploration – a quarter of a century of uninterrupted human presence on the International Space Station (ISS). This orbital station, which circles the Earth at an altitude of about 400 kilometers at an incredible speed of 28,000 kilometers per hour, is not only the most complex and expensive structure ever built by humanity, but also a unique laboratory that serves as a key springboard for the development of the low-Earth orbit economy and for NASA's next major steps in exploration, including ambitious crewed missions to the Moon and Mars. In anticipation of this silver anniversary, it is worth looking back at some of the scientific research that is, symbolically, linked precisely with silver, a noble metal whose properties have found surprising and crucial applications in space.

Silver as an ally in the fight against microbes in space

Silver has been used for centuries in the fight against infections, and its unique antimicrobial properties have today become an indispensable tool for suppressing the growth of microorganisms on the International Space Station. In a closed and isolated environment like the ISS, microbes pose a constant and serious threat. Over time, they form biofilms – sticky and resistant communities that can grow on almost any surface. Under space conditions, these biofilms can become extremely resistant to traditional cleaning agents, which poses a multiple danger. They can compromise water purification systems, damage sensitive equipment by causing corrosion, and, most importantly, pose a direct health risk to astronauts, whose immune systems are often weakened by their stay in microgravity.

One of the key research projects, known as Bacterial Adhesion and Corrosion, was focused specifically on studying the bacterial genes that contribute to the formation of these dangerous biofilms. The aim of the experiment was to test the effectiveness of a silver-based disinfectant in limiting their growth. The results showed that silver has exceptional potential in maintaining hygienic conditions on the station, paving the way for the development of new strategies for controlling the microbial environment on long-duration space missions.

Another experiment took the application of silver a step further, focusing on the production of silver nanoparticles directly on the space station. Silver nanoparticles, due to their microscopic size, have a significantly larger surface-to-volume ratio compared to larger particles. This allows silver ions to come into contact with a larger number of microbes, making them a much more effective antimicrobial tool. The goal of this research was twofold: first, to develop a more powerful agent to protect crew health from potential infections on future journeys, for example, to Mars. Second, to assess whether silver nanoparticles produced in microgravity conditions are more stable and more uniform in size and shape. It is precisely such more perfect characteristics that could further enhance their effectiveness, not only in space but also in numerous applications on Earth, from medicine to industry.

Wearable technology with silver for monitoring astronaut health

Silver is not only a powerful fighter against microbes but also a noble metal with extremely high conductivity and great stretchability, making it an ideal material for use in smart garments. NASA astronauts on the orbital laboratory tested a wearable monitoring vest equipped with silver-coated sensors. The purpose of this advanced garment was to record key vital signs – heart rate, cardiac mechanics, and breathing patterns – while the astronauts were sleeping.

Sleep quality is of crucial importance for the health and performance of astronauts, but it is often compromised due to stress, noise, and the unusual living conditions in microgravity. Traditional health monitoring methods can be cumbersome and interfere with sleep. This smart vest, however, is lightweight and comfortable, designed not to disturb sleep quality. The data collected by the silver sensors provided scientists with invaluable insight into how the space environment affects the cardiovascular and respiratory systems during rest. These findings are key to developing strategies for improving astronaut sleep, which directly impacts their ability to perform complex tasks and maintain long-term health. Technology developed for space often finds its way to applications on Earth, and such systems could revolutionize the remote monitoring of patients and athletes.

Silver crystals from space for the future of nanotechnology

The unique environment of microgravity, where there is no clear sense of "up" and "down," and weightlessness prevents the settling of particles, profoundly affects physical and chemical processes. Researchers use these unusual conditions to grow crystals that are significantly larger and have a more regular structure than those possible to obtain on Earth. On our planet, the force of gravity and processes like convection and sedimentation, which separate mixtures by density, inevitably introduce imperfections into the crystal lattice.

Within the NanoRacks-COSMOS research, scientists utilized the environment on the International Space Station to grow and analyze the three-dimensional structure of silver nitrate crystals. The goal was to obtain crystals of superior quality, free from defects caused by gravity. Studying the molecular structure of these nearly perfect silver nitrate crystals has enormous potential for application in nanotechnology. One of the most promising applications is the creation of silver nanowires, which are key components for the development of nanoscale electronics. These ultra-thin conductive threads could enable the production of smaller, faster, and more efficient electronic devices, opening a new chapter in the development of technology. This project is a perfect example of how fundamental scientific research in space can spur revolutionary innovations on Earth.

A quarter of a century on the threshold of a new era of exploration

As we count down to the silver jubilee, it is important to look at the bigger picture. Twenty-five years of continuous human presence in orbit is not just a technical achievement; it is a testament to endurance, innovation, and, above all, international cooperation. More than 20 countries have participated in the ISS project, and thousands of scientists, engineers, and astronauts have contributed their knowledge and work to this station. It has become a global symbol of what humanity can achieve when it works together. More than 3,000 scientific experiments have been conducted on the station in the fields of biology, physics, astronomy, and human physiology, which have advanced our understanding of life on Earth and beyond.

All the research, including that based on silver, is not an end in itself. It represents the foundation on which future, even more ambitious missions are built. Every experiment that helps protect astronaut health, every new material tested in extreme conditions, and every piece of knowledge about the human body's adaptation to space directly contributes to preparations for the return to the Moon through the Artemis program and, finally, for the historic leap – sending a human crew to Mars. The International Space Station is slowly approaching the end of its operational life, with a planned controlled deorbiting around 2031, but its legacy is just beginning. It has laid the groundwork for a new generation of commercial space stations and ensured that human presence in space becomes permanent, opening the door to a future where the frontiers extend far beyond our planet.