The Torino, H6, meteorite shower

Abstract

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 3He, 21Ne and 126Xe yield an exposure age of about 48 Ma. The cosmic ray track densities in three fragments range between 1.8 to 5 × 105/cm2 suggesting about 99% mass ablation in the atmosphere. Twelve radioisotopes with half lives ranging between 5.6 days to 7.3 × 105 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 (24Na, 48Cr, 57Ni, 47Sc, 47Ca, 59Fe, 42Ar and 44Ti) 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 60Co, 26Al and other radionuclides.

Cosmogenic radionuclides in the recently fallen Kobe (CK4) meteorite.

“…Gamma-ray spectrum was recorded starting 17:25 pm on September 27th (21 hours after the Bhandari et al (1989);…”

Devgaon (H3) chondrite: Classification and complex cosmic ray exposure history

“…A complex exposure due to fragmentation in space within the past 1 Ma will still have some 26 Al surviving from the previous exposure as a large body (40-50 cm) and could result in 22 Na/ 26 Al lower than expected. Thus, a recent Bhandari et al (1989). b Bonino et al (2001).…”

“…The second set of measurements were used to determine the activity of all the cosmogenic radionuclides using 40 K (K = 804 ppm; Table 2) as an internal standard following the procedure of Bhandari et al (1989). The measured activities are given in Table 9.…”

“…The intensity of galactic cosmic rays is anticorrelated with the sun spot number due to the accompanying changes in the intensity of the heliospheric magnetic field. The neutron monitor count rates, N m , enable us to compute the time variation of nuclide production rates, since the nuclide production rates are directly related to the neutron monitor count rates (Bhandari et al 1989). We have used the Climax neutron monitor data and numerically integrated the nuclide production to obtain their expected time variation over the past four decades.…”

“…We have used the Climax neutron monitor data and numerically integrated the nuclide production to obtain their expected time variation over the past four decades. A small phase lag, relative to the neutron monitor count rates, occurs in the activity of radionuclides with half-life smaller or comparable to the solar cycle, depending on their half-life (Evans et al 1982;Bhandari et al 1989;Bonino and Castagnoli 1997) while the production of the long lived radionuclides are not affected by the solar cycle. In light of these calculations, we now discuss the salient features of the observed activity pattern of radioactivities in the Devgaon meteorite.…”