What microgravity
does to the human body
Leaving gravity behind reshapes nearly every physiological system — from the heart to the skeleton to the mind. A free, interactive atlas of how astronauts adapt, what it costs them, and the medicine that keeps them alive.
One body, four phases, zero gravity
Follow the physiological clock from the launch pad to landing day. Tap a phase to see which systems are under stress — and why.
Three G's, then nothing
Ascent pins the crew into their seats at up to ~3G as the vehicle accelerates. Within minutes the engines cut off — and gravity, for the body's purposes, simply disappears. The adaptation clock starts ticking immediately.
Pick a system and see how it adapts
Each free module pairs a scroll-driven explainer and an animated before/after comparison with a deep dive, key terms, a self-test, and a real flight-surgeon clinical case.
Why space physiology is medicine's most extreme stress test
Spaceflight compresses years of physiological change into months. The heart remodels, bone dissolves, the inner ear loses its reference, and radiation accumulates with no atmosphere to absorb it. Understanding these adaptations doesn't just protect astronauts — it sharpens our grasp of aging, disuse, fluid balance, and bone disease back on Earth.
As missions stretch toward the Moon and Mars, keeping humans healthy becomes the limiting factor. That makes space medicine one of the most interdisciplinary frontiers in clinical science.
How crews hold the line against space
Every adaptation has a countermeasure in development. None are perfect — and the gaps that remain define the medicine of deep-space exploration.
Reload the skeleton
~2.5 hours of daily resistive and aerobic exercise on the ARED, treadmill, and cycle ergometer — sometimes paired with bisphosphonates — to slow bone and muscle loss.
Defend blood volume
Fluid and salt loading before re-entry, compression anti-G garments, and in-flight lower-body negative pressure to preserve plasma volume and baroreflex tone.
Shelter from storms
Passive shielding, dedicated storm shelters for solar particle events, and dose monitoring — though galactic cosmic rays remain the hardest unsolved problem for Mars.
Protect the mind & clock
Engineered lighting to anchor circadian rhythm against 16 sunrises a day, structured sleep, and behavioral-health support for isolation and confinement.
The questions everyone asks
Quick, plain-language answers to the things people most want to know about the human body in space.
Mostly no. The majority of changes — fluid shifts, heart remodeling, balance disturbance, even much of the muscle loss — reverse over weeks to months back on Earth. The concerns are the changes that may not fully recover, such as some bone density and certain eye (SANS) findings, plus the cumulative cancer risk from radiation on very long missions.
Resources & further reading
Curated, authoritative starting points to explore space medicine beyond this atlas. All links open in a new tab.
Human Research Program
NASA's hub for the science of keeping astronauts healthy on long-duration missions, including the five hazards of spaceflight.
The Human Body in Space
An accessible overview of how microgravity and radiation affect every major physiological system.
The Twins Study
The landmark study comparing astronaut Scott Kelly after a year in space with his identical twin on Earth.
Human & Robotic Exploration
The European Space Agency's research on life sciences, physiology, and preparing crews for the Moon and Mars.
Bone & Muscle Loss in Microgravity
How and why the weight-bearing skeleton and antigravity muscles waste away — and what's done about it.
Space Physiology Literature
Search peer-reviewed research on spaceflight physiology, SANS, and radiation biology in the open biomedical archive.