Abstract

The Lost City meteorite was photographed in flight and recovered by the Prairie Network. Four fragments totaling 17 kg have been found. Photometric and trajectory data for the Lost City meteor and for a subsequent meteor (no. 40617) with similar flight characteristics are used to establish a preliminary calibration of the mass scale of other fireballs. There is excellent agreement between the photometric masses derived from the most recent determination of the luminous efficiency of the meteoric process and the dynamic masses determined from the trajectory and the shape of the recovered meteorite. It is unlikely that photometric masses are overestimated by as much as a factor of 8 for objects of the size and composition of Lost City. Previous values for meteoroid bulk densities may have been seriously underestimated (by a factor of 5 or 8) if the flattened shape observed for Lost City and inferred from 40617 is common among meteoroids. An analysis of a third meteor, no. 40503, is presented as a counterexample to the above argument. This meteor of 100 times the intensity of Lost City reached maximum light and then was extinguished nearly instantaneously. We recognize that this is a different kind of meteoroid but have no satisfactory explanation for its behavior. The orbits of these meteors are similar to those of most other fireballs.