Radon on Mars and the Moon derived from Martian and lunar meteorites.

The radioactive gas radon-222, a fluid and aerosol tracer in Earth's lithosphere and atmosphere, can also reveal subtle rock physics processes in extraterrestrial environments, such as those involving water, but remains poorly constrained in planetary bodies due to the limited number of samples available. Here we measure the effective radium-226 concentration (EC) of six Martian and nine lunar meteorites to derive radon source terms for Martian and lunar rocks. EC values are 0.