Why Two Astronauts Are Spending a Full Year Aboard the International Space Station

Space · Published 8 October 2026 Swipe more like this →

In short: In March 2015, NASA astronaut Scott Kelly and Roscosmos cosmonaut Mikhail Kornienko launched to the International Space Station for a historic one-year mission. This unprecedented joint U.S.-Russian endeavor serves as a vital stepping stone for human exploration, specifically testing how the human body endures long-duration spaceflight before future missions to Mars.

The mission, which began with a launch from the Baikonur Cosmodrome in Kazakhstan on March 27, 2015, represents a critical shift in how space agencies approach long-term human health management. While previous expeditions typically lasted about six months, the one-year duration allows researchers to gather extensive data on the physiological and psychological impacts of extended microgravity exposure. This research is essential for mitigating risks associated with the much longer transit times required for deep-space exploration.

Aboard the station, Kelly and Kornienko participate in a wide array of scientific investigations. These studies range from molecular biology to physical science, focusing on how microgravity affects cellular function, bone density, and immune system performance. For instance, experiments like Osteo-4 examine bone loss, providing insights that benefit both astronauts and patients on Earth suffering from osteoporosis. Similarly, studies on in-flight infections help ensure that crews remain healthy and capable during the rigors of extended missions.

Beyond human biology, the station serves as a testbed for cutting-edge robotics and infrastructure. During the same period, crews have tested synthetic muscle polymers—materials that mimic biological contraction—to improve robotic dexterity for dangerous tasks. Furthermore, the station has undergone structural upgrades, including the installation of new docking adapters to accommodate future commercial spacecraft. By integrating these technological demonstrations with long-duration human health studies, the Expedition 43 crew and their successors are effectively mapping the requirements for humanity's next giant leap toward Mars.

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