Astronauts Suni Williams and Butch Wilmore, originally scheduled for an eight-day mission on the Boeing Starliner in June 2024, found themselves unexpectedly staying on the International Space Station (ISS) for nine months due to technical issues. This extended stay, while challenging, provides valuable insights into the effects of prolonged space travel on the human body.
Drawing on the experiences of astronauts like Frank Rubio, who spent 371 days on the ISS, and Russian cosmonauts Oleg Kononenko and Nikolai Chub, who broke the record for the longest ISS stay at 374 days, scientists are gaining a clearer picture of the physical changes astronauts undergo in microgravity.
Physical Changes in Space
- Muscle and Bone Loss:
- Microgravity causes rapid muscle and bone mass reduction, with muscles crucial for posture being most affected.
- Astronauts can lose up to 30% of muscle mass in extended missions and 1-2% of bone mass monthly.
- To counteract this, astronauts engage in 2.5 hours of daily exercise, including resistance training and cardio, and take dietary supplements.
- Spinal Elongation and Back Pain:
- The absence of gravity can cause spinal elongation, leading to increased height and potential back pain.
- This can also result in slipped disks upon return to Earth.
- Weight Loss and Nutritional Challenges:
- Maintaining a healthy weight in space is difficult, despite NASA’s efforts to provide diverse and nutritious food.
- Astronauts like Scott Kelly experienced significant weight loss during long stays on the ISS.
- Vision Changes:
- Fluid shifts in microgravity can cause blood to accumulate in the head, leading to vision problems such as decreased sharpness and structural eye changes.
- Exposure to cosmic rays and solar particles can also affect vision.
- Neural Adaptation:
- While cognitive performance remains relatively stable, astronauts may experience temporary decreases in speed and accuracy upon return to Earth.
- Brain structure can also change, with alterations in neural connectivity and ventricle swelling.
- Astronauts must relearn movement, and orientation without gravity.
- Gut Microbiome Alterations:
- The gut microbiome undergoes significant changes in space due to altered diet, environment, and exposure to radiation.
- Recycled water also plays a role.
- Skin Sensitivity:
- Astronauts may experience increased skin sensitivity and rashes upon return, possibly due to a lack of skin stimulation in space.
- Genetic Changes:
- Space travel affects telomere length, with elongation during spaceflight and rapid shortening upon return.
- Changes in gene expression related to DNA damage, bone formation, and immune response have also been observed.
- Research has shown differences in how male and female immune systems react to spaceflight.
- Immune System Effects:
- Astronauts may experience decreases in white blood cell counts due to radiation exposure.
- Vaccines have shown to react normally.
Ongoing Research and Future Implications
Research on astronauts like Frank Rubio and the SpaceX Inspiration 4 crew provides crucial data for planning future long-duration missions, such as those to Mars. Understanding the physiological effects of space travel is essential for ensuring the health and safety of astronauts venturing further into the Solar System.
