THE EXPLOSION OF THE BOLIDE OVER LUGO-DI-ROMAGNA (ITALY) ON 19 JANUARY 1993

A spectacular fireball was observed crossing Northern Italy from SE to NW on 19 January 1993, at about 00.33 h UT, ending with an explosion approximately over the city of Lugo di Romagna. Calculations on the fr agmentation of the body were performed for an entry velocity of 25 km s-1, a low-inclination of about 14-15-degrees, and a material strength S = 10-50 MPa (Bronshten, V. A., Physics of Meteoric Phenomena. Reide l, 1983) valid for stony (and carbonaceous) chondrites, with heights o f first fragmentation h(break) less-than-or-equal-to 35-40 km. For est imated visual magnitudes M(upsilon) = -22 to -25 at the peak of the li ght-curve corresponding to values of an initial radius of 1.5-3 m (Hil ls, J. K. and Goda, M. P., Astron. J. 105, 1114-1144, 1993), a meteor luminosity ranging between 300 and 4000 GW is obtained, consistent wit h the radiant flux values obtained by the Stefan-Boltzmann law for a b lack-body temperature of tens of thousands degrees. The explosion of t he bolide produced low-frequency (1.5-2 Hz) infrasonic waves which wer e monitored by a microseismic network of three stations near Ferrara a nd by regional seismic stations of the ING (Istituto Nazionale di Geof isca) at 20-60 km horizontal distances from the epicentre located in t he stratosphere. Microanalysis of recovered particles in the explosion zone, in the form of spherules of vaporized and recondensed material, reveals the relative importance of light chemical elements typical of soft structures.