Astrophysics with Radioactive Isotopes

Cosmogenic isotopes activity measured in Cavezzo, an anomalous L5 chondrite recovered in Italy

Not scheduled

20m

Oral Presentation

Speaker

Dr Dario Barghini (INAF – Osservatorio Astrofisico di Torino, Pino Torinese, Italy)

Description

On January 1st 2020, eight cameras of the PRISMA fireball network detected a very bright bolide over the skies of northern-central Italy. Thanks to these observations, we were able to locate a strewn-field of few square kilometers and recover two specimens, weighing 3.1 g (F1) and 52.2 g (F2), just three days after the fall.
Laboratory analysis on the Cavezzo meteorite showed substantial differences in the lithology, geochemistry, and oxygen isotopic composition of the two specimens. These results led to the classification of Cavezzo as a L5-anomalous chondrite, making it unique and representing a new meteorite type.
Measurements of gamma activity were performed on the main mass F2 at the Monte dei Cappuccini underground Research Station (Torino, Italy) with a large-volume and highly selective HPGe-NaI(Tl) spectrometer, revealing the presence of fifteen cosmogenic isotopes. The detection of short-lived radionuclides, with half-lives down to few days (e.g., V-48), confirmed the recent fall of the sample. Long-lived cosmogenic isotopes concentration (e.g., Al-26) allowed us to estimate the pre-atmospheric size of the meteoroid and the shielding depth of the meteorite. Furthermore, the activity of cosmogenic isotopes with a decadal and centennial half-life, such as Na-22 and Ti-44, revealed past solar activity variations on different time scales.
In this contribution, we present the results of the gamma-activity measurement of Cavezzo and the techniques developed for the detection of low activity cosmogenic radionuclides, below 0.1 decay per minute. Using the radioactivities measured in Cavezzo, we can characterize the galactic cosmic ray fluxes during the last solar minimum.