Spectactular fall of the Kendrapara H5 chondrite

Abstract

An extremely bright fireball was seen for over 250 km near the eastern coast of India in the evening sky on September 27, 2003. In a rare observation, the fireball was seen by two airline pilots, providing direction of the trail with reasonable accuracy, consistent with ground-based observations. A few fragments of the meteorite were subsequently recovered along the end of the trail in different parts of Kendrapara district (20°30' N; 86°26' E) of Orissa. Based on petrography and chemical composition, the meteorite is classified as H5 chondrite. The cosmogenic radionuclides 54Mn, 22Na, 60Co, and 26Al and tracks have been studied in this stony meteorite. Two of the fragments show an unusually high activity of 60Co (~160 dpm/kg) indicating a meteoroid radius of 50-150 cm. Assuming that less than 10% (by weight) of the fragments could be recovered because of difficult terrain, an atmospheric mass ablation of >95% is estimated. Based on the observations of the trail and the estimated mass ablation, orbital parameters of the meteoroid have been calculated. The aphelion is found to lie in the asteroidal belt (1.8-2.4 AU), but the inclination of the orbit is large (22°-26°) with respect to the ecliptic. Noble gases have been analysed in two samples of this meteorite. He and Ne are dominantly cosmogenic. Using production rates based on the sample depth derived from 60Co content, 21Ne-based exposure age of 4.50 ± 0.45 Ma is derived for Kendrapara. One of the samples, known to be more deeply shielded based on high 60Co activity, shows the presence of 80Kr, 82Kr, and 128Xe produced by (n, γ) reaction on 79Br, 81Br, and 127I, respectively. The (80Kr/82Kr)n ratio of 3.5 ± 0.9 is consistent with neutrons being mostly thermal. Trapped 84Kr and 132Xe are in the expected range for metamorphic grade H5.