Is Space Trying to Kill Us? (Radiation)
Earth’s magnetic field and atmosphere deflect an extraordinary quantity of high-energy particles every single day. We built civilisation on top of this protection and never once put up a sign. Step outside it, and the universe doesn’t object — it simply continues doing what it was already doing.
The numbers, briefly: The average person on Earth receives roughly 2–3 millisieverts of radiation per year. A six-month stay on the International Space Station delivers up to 160. A return trip to Mars: over 1,000. The universe is not in a hurry. It has time.
Where It Comes From
Space radiation arrives from two main directions: the Sun, which produces a continuous stream of charged particles and occasional violent bursts requiring immediate shelter, and the rest of the galaxy, which produces galactic cosmic rays — originating from supernovae and black holes, travelling for millions of years, and passing through spacecraft walls with minimal interest in what’s inside.
Why It’s Different
This isn’t a more intense version of a dental X-ray. High-energy heavy ions — iron nuclei moving at a substantial fraction of the speed of light — cause clustered DNA damage the body struggles to repair. Your cells are well-equipped for Earth. They are considerably less prepared for a subatomic projectile from an exploded star.
What We’re Doing About It
Shielding helps, with caveats. Aluminium — the standard spacecraft material — is not particularly effective against galactic cosmic rays. Water and polyethylene do better. Lunar regolith does better still. The most sophisticated protection strategy currently available for surface habitats is, in certain respects, a cave. Humanity spent forty thousand years in caves, invented rocketry, and has now concluded that caves were onto something.
Artemis and What Comes Next
NASA’s Artemis programme is the first return of humans to deep space since 1972 — and this time we’re bringing better instruments and considerably more questions. Aboard Artemis I, two human-shaped phantoms named Helga and Zohar rode into deep space to measure organ-level radiation exposure so future crews wouldn’t have to find out the hard way. They were not consulted on the mission parameters.