Atmospheric Fragmentation of the Gold Basin Meteoroid as Constrained from Cosmogenic Nuclides

Since the discovery of the Gold Basin L4 chondrite shower almost ten years ago in the northwestern corner of Arizona, many thousands of L-chondrite specimens have been recovered from an area of approx.22 km long and approx.10 km wide. Concentrations of cosmogenic 14C and 10Be in a number of these samples indicated a terrestrial age of approx.15,000 years and a large pre-atmospheric size [1]. Additional measurements of cosmogenic Be-10, Al-26, Cl-36, and Ca-41 in the metal and stone fractions of fifteen Gold Basin samples constrained the pre-atmospheric radius to 3-5 m [2]. This implies that Gold Basin is by far the largest stone meteorite in the present meteorite collection, providing us with an opportunity to study the fragmentation process of a large chondritic object during atmospheric entry. Knowledge about the fragmentation process provides information about the mechanical strength of large meteoroids, which is important for the evaluation of future hazards of small asteroid impacts on Earth and possible defensive scenarios to avoid those impacts.