At 12:30 P.M. in Estonian SSR, sonic booms were heard and stones fell at Aukoma, Kurla, Wahhe, and Sawiauk. The weight of these stones was ~14 kg, 7.5 kg, 1.5 kg, and 0.25 kg. These falls are also known by the names of Pilistvere and Pillistvere.
Enstatite chondrites were formed in a highly reducing environment. Therefore, they contain virtually no metal in the oxide form—an amount much less than other chondrites, and even the terrestrial planets. The mineral sinoite (silicon oxynitride) has been found to occur in Pillistfer and many other EL chondrites that have a high bulk N content. Sinoite is associated with crystallization from an impact melt, or alternatively, with metamorphic processes. This suggests that Pillistfer experienced a period of high, possibly melt-forming temperatures, followed by one in which annealing occurred, and finally, it was shocked to stage S2.
Oxygen isotopic studies place the formation of enstatite chondrites on the terrestrial fractionation line, which is taken by some to mean that they formed within the inner Solar System. Based on Mn–Cr isotope systematics and its correlation with heliocentric distance, Shukolyukov and Lugmair (2004) concluded that E chondrites originated ~1.0–1.4 AU from the Sun before being perturbed into their present locations in the asteroid belt. Similarly, Nakashima et al. (2006) calculated a heliocentric distance of >1.1 and 1.3 AU for two EL3 chondrites (ALH 85119 and MAC 88136, respectively) on the basis of their implanted solar noble gas concentrations.
In contrast, the identification of the E-asteroid group, including Hungaria at 1.94 AU, Nysa at 2.42 AU, and Angelina at 2.68 AU, suggests that the actual solar region of formation may lie at a greater heliocentric distance. Cosmochemists are presently trying to construct a suitable theory involving oxygen depletion in this E-asteroid region of the Solar System to explain the conflicting theories. The specimen pictured above is a 5.7 g partial slice showing the abundant free metal that characterizes this group.
