The Torino, H6, meteorite shower

Abstract— A meteorite shower fell at Torino, Italy on 18 May 1988. Petrographic studies indicate that the stone is an H6 chondrite having features of moderate to severe shock. Chemical analyses of the meteorite are reported. Cosmic ray produced 3 He, 21 Ne and 126 Xe yield an exposure age of about 48 Ma. The cosmic ray track densities in three fragments range between 1.8 to 5 × 10 5 /cm 2 suggesting about 99% mass ablation in the atmosphere. Twelve radioisotopes with half lives ranging between 5.6 days to 7.3 × 10 5 years have been measured with high precision (2 to 10%). Marginal signals were observed for several short‐lived nuclides and upper limits were obtained for the activity levels of eight radionuclides ( 24 Na, 48 Cr, 57 Ni, 47 Sc, 47 Ca, 59 Fe, 42 Ar and 44 Ti) some of which have not been hitherto detected in fresh falls. The data are generally consistent with the nuclide production by galactic cosmic rays when modulation due to the solar cycle is taken into consideration. The preatmospheric radius of the chondrite is estimated to be 20 cm, consistent with track densities and activity levels of 60 Co, 26 Al and other radionuclides.