The Space Collector "Earth".

When they are ejected into the interplanetary medium during interasteroidal collisions, meteorites have a limited lifetime in space, which is scaled by their "cosmic-ray exposure ages" inferred from the concentrations of cosmogenic nuclides such as 3He, 21Ne and 38Ar, produced during the nuclear reactions of galactic cosmic rays with the constituent atoms of meteorites. Such ages range from about 10 to 500 Myr, with the notable exception of the shorter age of the CI- and CM-type hydrous-carbonaceous chondrites (see Sect. 22.3). Consequently, meteorites have to be constantly replenished upon interasteroidal collisions. [ABSTRACT FROM AUTHOR]