Mars missions pose serious, unresolved health risks
Mar 4th 2026
Radiation, microgravity and isolation create medical harms that current countermeasures only partly address, leaving long-duration Mars or Moon habitation medically risky and uncertain.
- A three-year, crewed Mars mission could expose astronauts to roughly 3,600 chest X-rays worth of radiation, far above the 240 to 480 X-rays typical on a six-month stay aboard the ISS.
- Microgravity causes about 1 percent bone density loss per month and progressive muscle wasting despite daily exercise regimens.
- A 2024 study found that just one month in microgravity can alter kidney pathways in ways that may be permanent.
- Astronauts who spend months in space show arterial and endocrine changes consistent with many years of aging.
- Existing countermeasures such as exercise, medications, and shielding reduce but do not eliminate these health harms.
- Most human data come from six-month or shorter stays in low Earth orbit, so the health effects of yearlong or multi-year deep space missions remain largely unknown.