After spending nine months aboard the International Space Station (ISS), astronauts Suni Williams and Butch Wilmore have finally returned to Earth. Their journey back from space may be complete, but the process of adapting to gravity again has just begun. The human body undergoes significant changes in space, from weakened muscles to vision problems, and recovering from these effects can take months. Here’s a deep dive into how zero gravity impacts astronauts and the rehabilitation process they undergo upon return.
How Does Zero Gravity Affect the Human Body?
Spending extended periods in space has profound effects on the body due to the absence of gravity. While astronauts exercise regularly to minimize deterioration, some effects are inevitable.
1. Muscle and Bone Loss
- In microgravity, muscles do not work as hard since they are not required to support body weight.
- Astronauts lose muscle mass, particularly in their back, thighs, and calves.
- Bones weaken at a rate of about 1-1.5% mineral density loss per month, increasing the risk of fractures and kidney stones.
- Even after returning to Earth, some astronauts never fully regain lost bone density.
2. Vision Impairment
- Fluid shifts toward the head due to microgravity, leading to increased pressure on the eyes.
- This condition, called Spaceflight-Associated Neuro-ocular Syndrome (SANS), can cause vision changes that persist even after returning.
3. Cardiovascular and Immune System Changes
- The heart weakens since it does not have to work as hard against gravity.
- Blood circulation changes, causing dizziness and balance issues upon return.
- The immune system weakens, making astronauts more susceptible to illnesses.
4. Radiation Exposure
- Without Earth’s protective atmosphere, astronauts absorb up to 10 times more radiation, increasing the risk of cancer and cognitive decline.
- Long-term space missions, such as trips to Mars, pose even greater risks.
How Astronauts Recover on Earth
The transition back to Earth’s gravity is not immediate. Astronauts undergo months of rehabilitation to regain strength and balance. Here’s a timeline of how the body recovers:
Immediate Effects (First Week After Landing)
- Balance issues and dizziness due to the body readjusting to gravity.
- Motion sickness as the inner ear struggles to regain equilibrium.
- Blood pressure fluctuations as circulation returns to normal.
Two Weeks Post-Landing
- The immune system strengthens, and astronauts start regaining lost body fluids.
- Red blood cell production stabilizes, reducing fatigue and weakness.
One Month After Return
- Muscle reformation is nearly complete, and strength levels approach pre-flight conditions.
Three Months Post-Mission
- Skin cells regenerate, and body mass stabilizes.
- Vision issues improve, but some effects may persist long-term.
Six Months After Landing
- Bone strength remains lower than before space travel, posing long-term risks of fractures.
- Increased risk of cancer remains due to prolonged radiation exposure.
- Genetic changes caused by space travel begin returning to normal, but 7% of genes may remain altered permanently.
What Science Still Doesn’t Know
While NASA has studied space travel’s effects for decades, many unanswered questions remain, especially concerning long-duration missions. Scientists are still investigating:
- How microgravity affects lung function.
- The exact mechanisms behind radiation-induced damage and accelerated aging.
- The long-term mental health effects of prolonged space travel.
Returning from space is more than just a landing—it’s a slow and complex journey back to full health. Despite rigorous training and exercise routines, astronauts face months of rehabilitation to recover their strength, balance, and overall well-being. As space agencies prepare for future missions to the Moon and Mars, understanding and mitigating the effects of zero gravity on the human body remains a top priority.
