How dangerous is space radiation for astronauts heading to Mars?
A 3-year Mars mission could expose astronauts to more than ten times the dose of a six-month stay on the space station.
Space radiation is dangerous enough to be one of the main roadblocks to sending people to Mars: the risk of cancer caused by radiation exposure is one of the main obstacles to interplanetary travel, and the Sun is only part of the problem. Astronauts get about 72 on a six-month stay on the International Space Station. A 3-year mission to Mars has the potential to expose them to over 1000 millisieverts, because beyond Earth's magnetic field the rate of exposure is dramatically higher. Cancer risk from is well documented at doses beginning at 100 millisieverts.
Radiation doses in the text
| millisieverts | |
|---|---|
| ISS, 6 months | 72 mSv |
| Cancer risk documented from | 100 mSv |
| Mars, 3-year mission (over) | 1,000 mSv |
Two sources matter. come from beyond the Solar System and are mostly highly energetic protons with a small component of heavy ions. Solar particle events, also called solar radiation storms, happen when particles from the Sun, mostly protons, are accelerated by a flare or by a coronal mass ejection shock. NOAA rates them from S1 (minor) to S5 (extreme). Energetic protons are a significant radiation hazard to spacecraft and astronauts.
Engineers do not yet have an easy answer. The largest difficulties are large uncertainties in the cancer risk estimates, no simple and effective , and no way yet to measure how well countermeasures work. NASA limits an astronaut's career risk to 3 percent of risk of exposure-induced death from fatal cancer, with 95 percent confidence that the limit is not exceeded, and a legal principle called requires keeping exposure as low as reasonably achievable. It remains an open engineering and medical problem.
Try it
How a daily dose adds up
y = 0.4x + 0
Challenge · At 0.4 mSv a day, six months (about 180 days) gives roughly the ISS's 72 mSv. Now find the daily dose that pushes a 3-year trip, about 1,100 days, past 1,000 mSv.
Quiz me
0/3
Recap
Beyond Earth's magnetic field, constant cosmic rays and occasional solar storms add up over a long trip, and nobody has a complete fix yet.
💡 A trick to remember it · Earth is a magnetic umbrella; leave it, and you need to bring your own.
Surprising fact · A 3-year Mars mission could expose astronauts to over 1000 mSv, against about 72 mSv for six months on the ISS.
Sources (3)
No source, no claim. Every fact in this lesson (16 claims) cites at least one of these.