LAUSR

Abstract Two Martian meteorites, Chassigny and Nakhla, were analyzed by non-destructive gamma-ray spectrometry to determine concentrations of cosmogenic (26Al) and primordial (40K, 238U, 232Th) radionuclides, and to estimate their pre-atmospheric sizes and cosmic-ray exposure ages. The pre-atmospheric radii of the Chassigny and Nakhla meteorites were estimated using the cosmogenic 26Al to be 17 ​± ​4 and 30 ​± ​5 ​cm, which would result in their total masses of 30–130 and 210–580 ​kg, respectively. This is comparable to the size and mass estimated for other chassignites and nakhlites. The cosmic-ray exposure ages of the Chassigny and Nakhla meteorites estimated using the 26Al – 21Ne isotope pair were 12.8 ​± ​2.5 and 11.6 ​± ​1.8 Myr, respectively, in agreement with published ages of chassignites and nakhlites averaged from several isotope methods, i.e. 11.6 ​± ​0.8 and 12.2 ​± ​0.8 Myr, respectively.