Material in space, whether in a meteoroid, asteroid or planetary object, is irradiated by solar
and galactic cosmic radiation. Meteorites and lunar samples preserve a history of this
irradiation. Depending on the half-life of the nuclide, the activity can be used to estimate
the exposure age of meteorites in space or also their terrestrial residence age from the decay
of radionuclides from the original activity. The terrestrial age can potentially give us
information about infall rates of material in the past. On the surface of the Moon, solar
cosmic rays produce radionuclides in the top few centimeters of rocks and this signal can be
used to infer past solar activity, from the production rates of different nuclides.
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