After spending an extended nine months aboard the International Space Station (ISS), NASA astronauts are met with a variety of physical challenges upon their return to Earth. Originally planned as an eight-day journey, astronauts Sunita “Suni” Williams and Barry “Butch” Wilmore found themselves staying far longer than anticipated. Their extended mission resulted from safety concerns regarding the Boeing spacecraft scheduled to bring them home. Ultimately, SpaceX stepped in, and the duo finally returned, experiencing Earth’s gravity after 286 days.
Reacclimating to life on Earth is not instantaneous. The human body undergoes profound changes in space, and these adjustments are not easily reversed. Gravity, once taken for granted, becomes an obstacle that the body needs to relearn how to navigate. Below are six key health concerns faced by astronauts after long durations in orbit.
Brain and Balance Disruptions
The absence of gravity leads to significant alterations in how the brain processes information. During their time in space, Williams and Wilmore likely endured space motion sickness and a temporary loss of spatial orientation. Over time, their brains adapted to microgravity. However, upon returning, that adaptation must once again shift.
According to research from Vestibular Science studies, astronauts often struggle with orientation, gaze control, balance, and locomotion when they first return to Earth. Their central nervous systems require time to recalibrate. Recovery usually occurs within days, but for those who have spent extended periods in space, full restoration may take weeks or even months. It is common practice for returning astronauts to be seated immediately after landing to ensure safety, as advised by experts at Baylor College’s Medicine Center.
Bone Density Decline
Bone loss remains one of the most pressing concerns for astronauts. In microgravity, bones weaken at an alarming rate. Dr. Tess Morris-Paterson, founder and managing director of Astro Perform, has highlighted that bone density decreases in space can mirror the effects of spending weeks bedridden on Earth.
The spine and pelvis are especially vulnerable, though the femur’s trochanter area is most affected, losing approximately 1.56% of its density each month. Over nine months, this could lead to up to a 14% reduction in those areas, despite strict workout routines designed to slow this decline. More concerning still is the slow recovery of non-weight-bearing bones, like the radius in the forearm, which often remain below pre-flight levels for up to a year after returning.
Additionally, calcium absorption decreases in space, resulting in elevated calcium levels in the urine. This can contribute to the development of kidney stones, a painful and potentially dangerous condition for returning astronauts.
Skin Sensitivity and Changes
The skin, too, suffers during prolonged space missions. Baylor College’s Medicine Center notes that reduced immunity in space, combined with microbial proliferation, can leave skin more susceptible to irritation.
Interestingly, the lack of pressure on astronauts’ feet means the bottoms of their feet lose their callouses and become soft. Meanwhile, callouses tend to develop on the tops of their feet, where friction from footholds is constant. This unusual redistribution of skin thickness reflects the body’s adaptation to a microgravity environment.
Radiation Exposure
Radiation poses an unavoidable danger in space. Astronauts are subjected to levels of radiation around 100 times higher than what is experienced on Earth. This exposure increases the risk of radiation sickness, neurological issues, and degenerative diseases.
Long-term, astronauts face a heightened likelihood of developing cancer. Protective shielding and careful monitoring can only go so far in mitigating these risks, making radiation one of the most persistent concerns for space travelers.
Muscle Mass Loss
Muscle atrophy occurs quickly in space, where daily activities no longer require the strength and resistance needed on Earth. Without regular exercise, muscles lose mass and function, especially in the legs and lower back.
This weakening increases the risk of falls and related injuries when astronauts return. Even with rigorous fitness regimens aboard the ISS, muscle recovery upon return is slow and requires months of dedicated rehabilitation.
Vision Impairment
Extended time in microgravity can also have unexpected consequences for vision. One common issue is swelling at the back of the eye, known as Spaceflight-Associated Neuro-ocular Syndrome (SANS). This swelling can lead to changes in eyesight, sometimes resulting in long-term vision problems.
Astronauts undergo regular eye exams and monitoring, but the exact causes of these ocular changes are still being studied. The concern remains significant enough to warrant ongoing research as space agencies prepare for even longer missions.
Psychological Effects and the Overview Effect
Spending nine months confined in space can weigh heavily on mental health. Isolation, monotony, and distance from family and friends challenge the psychological resilience of even the most seasoned astronauts.
One powerful phenomenon experienced by astronauts is known as the Overview Effect. This cognitive shift occurs when seeing Earth from space, fostering a sense of interconnectedness and awe, but also a sobering awareness of the planet’s fragility. NASA explains that this perspective changes how astronauts think about Earth and life itself.
Former astronaut Ron Garan described his experience of witnessing Earth from orbit as profoundly moving. He spoke of seeing a vibrant, living biosphere held together by an incredibly thin atmosphere. From space, the planet’s vulnerability is striking, reinforcing the importance of sustainability and the need for humanity to care for its only home.
Conclusion: The Long Road to Recovery
Returning from a nine-month journey aboard the ISS is not just a matter of stepping off a spacecraft. The body, having spent months adapting to microgravity, must slowly adjust to gravity’s pull once more. Muscles need to be rebuilt. Bones require time to regain density. The brain and vestibular system work to reestablish balance and coordination.
Meanwhile, the psychological impacts linger. The shift in perspective from the Overview Effect stays with astronauts, often inspiring them to advocate for environmental causes and broader global cooperation.
Medical teams on Earth work closely with returning astronauts, providing rehabilitation programs tailored to each individual’s needs. Recovery timelines vary, but the effects of prolonged space travel are clear. As space agencies prepare for longer missions, including potential trips to Mars, understanding and addressing these health concerns remain vital.
The human body is remarkably resilient. Yet, it is also fragile when removed from the conditions it evolved in. Each return from space is both a celebration of exploration and a reminder of the limits our bodies face beyond our planet. With every mission, scientists learn more about how to safeguard astronauts’ health, making future voyages safer and more sustainable.
