The Getafe rock: Fall, composition and cosmic ray records of an unusual ultrarefractory scoriaceous material

Abstract

In 1994 a moving car and its driver, on a highway in southern Madrid (Getafe), were struck by a falling rock. Eighty-one additional fragments (total weight: 55.926 kg) were later recovered, which all pointed towards a meteorite fall. A study of the composition of this object revealed an ultrarefractory material displaying a most unusual chemical make-up which differs from any known meteorite class, and for some elements and minerals approaches the composition of CAI (Ca-Al-rich inclusions in chondrites). A study of some cosmic-ray-produced stable and radioactive nuclides indicates: a) space and terrestrial exposure ages which do not exceed 1,000 and 520,000 years, respectively; b) the presence of a small ²²Ne excess (1,100°C fraction), which suggests either a nucleogenic contribution from the ¹⁹F(α,n)²²Ne reaction or a trapped Ne signature distinct from atmospheric Ne, and c) the existence of minor variations in the ³⁸Ar/³⁶Ar ratios also indicating a nucleogenic component or fractionation effects. ¹⁴C data are consistent with "modern" carbon originated in the period 1955-1958 and not earlier or more recently. The possibility that the Getafe rock could have a man-made origin (i.e. ceramic and refractory tiles, industrial slag) is also considered.