The human body cannot survive very well on other planets, other moons, or in outer space.

Judge as of 2026-03-04 against the space-medicine literature (NASA Human Research Program, peer-reviewed studies). True: the evidence shows that long stays off Earth cause serious physiological harm and need heavy life support, including microgravity bone and muscle loss, radiation exposure, cardiovascular and vision problems (SANS), and the lack of a breathable atmosphere and pressure on other bodies, so that humans do not fare well without major protection. Mostly true: there is broad support but some overstatement, for example humans have lived in orbit for over a year with countermeasures. Mixed: the evidence shows harms but substantial success at surviving in space with technology, leaving 'cannot survive very well' arguable. Mostly false: the evidence shows that with current technology humans manage long stays with only modest lasting harm. False: the evidence shows humans thrive in these environments without significant harm.

Set before the research began.

1. E1 Effects of Spaceflight on Musculoskeletal Health: A Systematic Review and Meta-analysis, Considerations for Interplanetary Travel PMC (peer-reviewed systematic review and meta-analysis) · 11 June 2021

   “small to moderate reductions in BMD were evident post long-duration spaceflight (Hedges g = − 0.23”

2. E2 Spaceflight associated neuro-ocular syndrome (SANS) and the neuro-ophthalmologic effects of microgravity: a review and an update - npj Microgravity Springer Nature (npj Microgravity) · 7 February 2020

   “To date approximately 15% of astronauts had clinically significant (Frisén grade 1–3) ODE after LDSF (private communication William Tarver, MD).”

3. E3 Hazard: Space Radiation - NASA NASA Human Research Program · 26 October 2023

   “Radiation exposure increases cancer risk, damages the central nervous system, can alter cognitive function, reduce motor function, and prompt behavioral changes.”

4. E4 The Real Story About Astronaut Health Care in Space - NASA NASA · 21 November 2024

   “NASA and its international partners have maintained a continuous human presence aboard the space station for more than 24 years, conducting research that is not possible on Earth.”

The peer-reviewed literature reports physiological harm from long-duration spaceflight: bone mineral density loss (E1) and clinically significant optic disc edema in about 15% of astronauts (E2). NASA's Human Research Program states that space radiation exposure increases cancer risk and can damage the central nervous system and alter cognitive and motor function (E3). However, NASA and its partners have kept a continuous human presence aboard the space station for more than 24 years (E4), and E1 describes the bone losses as small to moderate. That makes 'cannot survive very well' somewhat overstated, which matches the criteria's description of mostly true.