Bolide AIDA: Death of an Aubrite Meteoroid

A bright, slow moving, bolide observed during the 1989 AIDA campaign is shown to have been a very unusual near-Earth meteoroid. Data were obtained with five different instruments and these observations have now been extensively analyzed. Various indicators point to a stony object and spectroscopic observations in the near IR show two Fe I emissions with an excitation temperature of 3100 K. A third feature due to Na I gives an abundance ratio of Na to Fe of 1:1 by number. Ionized calcium (which is often strong in the near UV), manganese, and cobalt appear to have been weak or absent. Based on the spectrum analysis, we conclude that the object was an enstatite meteoroid and the lack of Mn compared with Fe and Na suggests an aubrite composition. The lightcurve, aerodynamic analysis, and video images show the object underwent extensive fragmentation at virtually all points of its trajectory.