Answer to Question #753 Submitted to "Ask the Experts"

Q

Why were the astronauts, who traveled to the moon, not killed by exposure to radiation?

A

The radiation levels were too low to be lethal. Astronauts on Apollo missions were exposed to radiation from the Van Allen belts (trapped particles) and the galactic cosmic ray (GCR) background. There were no solar particle events of any significance during these missions; hence, there were no dose accumulations from them. Radiation exposures for the transits through the trapped belts were kept very low by transiting quickly through them. Since the Apollo mission lengths were only a week or two, there were also no significant accumulations of radiation dose from the GCR background. Thus doses were well below thresholds for any measurable radiation effects, including lethality. Average exposures to Apollo crews measured by onboard dosimetry were 4.1 mGy (0.41 rad) absorbed dose and 12 mSv (1.2 rem) dose equivalent for the mission duration.

Larry Townsend, PhD