On June 5, 2024, astronauts Butch Wilmore and Suni Williams embarked on what was expected to be a short, 10-day mission aboard the International Space Station (ISS). However, a malfunction with the thrusters turned their journey into a remarkable 286-day adventure. As they spent nearly 9 months in space, these astronauts became some of NASA’s longest-serving crew members on a single mission. But what happens to the human body when it spends so long away from Earth and immersed in the microgravity environment of space?
The effects of long-term space travel on astronauts’ bodies are more mind-blowing than you might expect. As we look at the physical changes that occur during prolonged space missions, it’s clear that space travel challenges the human body in ways we are just beginning to understand.
Immune System Changes: A New Frontier for Health
One of the first noticeable effects of extended time in space is a weakening of the immune system. Astronauts in space are more vulnerable to infections due to alterations in immune cell functions. Furthermore, dormant viruses in the body can reactivate, posing an additional risk to astronauts’ health. The immune system, which typically fights off harmful pathogens on Earth, behaves unpredictably in the low-gravity environment of space. Because of these risks, NASA closely monitors astronaut health during and after their missions, developing countermeasures to protect their well-being.
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Watch how two NASA astronauts escape a stuck SpaceX capsule—stream the video now!
Fluid Redistribution: The Struggle Against Microgravity
On Earth, gravity pulls bodily fluids downward, keeping everything in its place. But in space, this fluid distribution changes dramatically. Without gravity’s pull, fluids shift toward the upper body, resulting in noticeable facial puffiness and a sensation akin to having a perpetual cold. Astronauts often experience discomfort from this redistribution, which can also affect their vision. Fluid buildup inside the skull can increase pressure on the eyes, leading to temporary vision problems. These seemingly minor symptoms are just some of the challenges astronauts face when living in microgravity for extended periods.
Height Boost: A Surprising Effect of Weightlessness
A fascinating, though temporary, effect of living in space is the increase in height that astronauts experience. With no gravity to compress the spine, astronauts can grow up to 3% taller during their first few days in space. The absence of gravitational force allows the spine to elongate, making astronauts a bit taller than they are on Earth. However, this height gain is short-lived. As soon as astronauts return to the planet’s gravity, their spines return to their usual shape, and they quickly regain their normal height.
Vision Impairment: Spaceflight-Associated Neuro-ocular Syndrome
Astronauts on long missions often experience vision changes, including those caused by Spaceflight-Associated Neuro-ocular Syndrome (SANS). The fluid shifts in space can increase pressure inside the skull, which, in turn, can put pressure on the optic nerve. This may lead to swelling and changes in the shape of the eyeball, impairing vision. While some of these effects are temporary and improve once astronauts return to Earth, the potential for long-lasting vision problems remains a significant concern. Space agencies are researching solutions to mitigate these risks for future long-duration missions.
Changes to the Heart: The Impact of a Low-Gravity Environment
In space, astronauts’ hearts don’t have to work as hard as they do on Earth. The absence of gravity means the heart doesn’t have to fight against the downward pull of blood and fluids, leading to a decrease in heart muscle mass. Over time, this can result in low blood pressure and dizziness, particularly when astronauts return to Earth’s gravity. Fortunately, most astronauts can recover their heart strength with proper rehabilitation, though it can take time for their cardiovascular systems to return to normal.
Muscle Atrophy: The Price of Microgravity
In microgravity, muscles don’t have to work against gravity’s pull, which leads to muscle atrophy. Without regular exercise, astronauts can lose up to 20% of their muscle mass in just a few days. To counter this, astronauts are required to exercise for about two hours each day using specialized equipment. While exercise helps mitigate muscle loss, it’s not entirely avoidable. Astronauts often experience weakness and muscle soreness upon their return to Earth, requiring rehabilitation to regain full strength.
Increased Radiation Exposure: The Silent Danger in Space
One of the more serious risks of long-term space travel is increased exposure to cosmic radiation. In the absence of Earth’s protective atmosphere, astronauts are bombarded by radiation from the sun and outer space. Prolonged exposure can increase the risk of cancer and potentially cause cognitive decline. While the ISS offers some shielding from radiation, long-duration missions still pose significant risks. Understanding and mitigating the dangers of space radiation are essential for future missions, especially those heading farther from Earth, such as missions to Mars.
Bone Density Decrease: The Challenge of Bone Health in Space
Gravity plays a crucial role in maintaining bone strength. On Earth, the constant pull of gravity helps keep bones dense and strong. In space, however, the lack of gravitational force leads to a significant decrease in bone density, particularly in the hips and legs.
Astronauts can lose about 1% of their bone mass per month in space, a rate much higher than what is seen in elderly people on Earth who suffer from osteoporosis. This makes astronauts more vulnerable to fractures and bone injuries, posing a serious challenge for long-term space missions. To combat bone loss, astronauts undergo regular exercise, but it remains one of the most significant health concerns of space travel.
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Watch Sunita Williams and Butch Wilmore touch down on Earth after 286 days aboard the ISS with NASA and SpaceX!
Conclusion: The Ongoing Mystery of the Human Body in Space
Space travel is not only about exploring new frontiers and venturing beyond Earth; it’s also about discovering how our bodies react to extreme conditions. The human body’s response to microgravity, radiation, and other space-related factors is still not fully understood. While we have learned a great deal about how the body changes in space, many questions remain unanswered. As we continue to push the boundaries of space exploration, understanding these physiological changes will be key to ensuring the health and safety of astronauts during long-duration missions. There is much more to uncover about the effects of space on the human body, and every new mission brings us closer to understanding how we can adapt to life beyond Earth.
From improved technologies to better medical care, space agencies like NASA are working tirelessly to address the challenges astronauts face. As humanity sets its sights on the stars, it’s clear that the journey of understanding the human body in space is just beginning.
