Astronaut well-being has been a primary concern since the inception of space exploration. Challenges such as motion sickness, disorientation, muscle weakening, and bone density loss have impacted all space travelers. NASA has developed methods to address many of these issues using medication and rigorous exercise in space. However, potential severe health complications could impede longer missions to destinations like the moon and Mars. Scientists are actively researching the health risks that long-distance astronauts may encounter and how to mitigate them.
While serious health incidents in space are infrequent, the International Space Station witnessed its first medical evacuation in January 2026. Astronaut Mike Finke required ground-based medical attention for a non-life-threatening condition, marking a significant event in the station’s 25-year history. The cause of the emergency was not disclosed by NASA for privacy reasons, but Finke confirmed his recovery.
Close calls in space are closely analyzed to enhance our understanding of how microgravity impacts human health. A recent study by researchers at Simon Fraser University focused on blood clot formation in microgravity, prompted by a female astronaut’s clot discovery in 2019. The study revealed that blood clots in microgravity are more resilient than those formed on Earth, warranting further investigation into potential sex differences in blood clotting among astronauts.
Both Finke and the unnamed female astronaut were diagnosed using a portable ultrasound device aboard the space station. Weightlessness in space can lead to blood clot formation and other physiological changes. For instance, Canadian astronaut Bob Thirsk experienced vision deterioration in orbit, later identified as Space-Associated Neuro-Ocular Syndrome (SANS). SANS is attributed to alterations in blood flow and pressure affecting the eyes, with up to 70% of astronauts encountering this issue during long-term space missions.
Injuries are common in space, with musculoskeletal injuries documented in multiple NASA studies. The International Space Station is equipped with medical supplies and instruments akin to a hospital emergency department, including a well-stocked pharmacy and biomonitors. However, conditions requiring open surgery, like appendicitis, necessitate immediate return to Earth due to the challenges of surgical procedures in a weightless environment.
Future missions to the moon and Mars pose greater health care challenges, with longer return journeys and communication delays impacting medical support. NASA is devising the Earth-Independent Medical Operations (EIMO) strategy to enhance autonomous medical care for astronauts during distant missions. Emphasis is placed on proactive health monitoring and self-sufficiency to address potential health issues before and during space travel.
Despite these advancements, the possibility of unexpected medical emergencies or fatal injuries remains. NASA has detailed protocols in place, including utilizing a space suit as a temporary containment measure in case of astronaut fatality in space. The hope is to never have to implement such procedures.