Arthur A. Griffin

The frequency of meteorite falls on the earth

Photographic observations from a network of 60 cameras in western Canada are used to derive the influx rate of meteorites on the earths surface, the first time instrumental data have been used for this purpose. Forty-three observed events are believed to have dropped between 0.1 and 12 kilograms of meteorites each. The flux values are corrected for a minor latitude effect and agree with earlier estimates near 10 kilograms but vary more slowly with mass. Eight events per year drop at least 1 kilogram of meteorites in an area of 106 square kilometers.

Meteorite Orbits from Observations by Camera Networks

Camera networks for the study of bright fireballs now have a history approaching two decades• It was hoped that the networks would produce a statistically significant group of recovered meteorites with accurate orbits. Due to the great difficulty in locating the meteorites from a photographed event, there are still only three meteorites with orbits determined from suitable photographs; Pribram, Lost City and Innisfree (Ceplecha I96I, McCrosky et al. 1971, Halliday et al. 1978, respectively). Networks do, however, provide an alternative approach to the problem. Instead of determining approximate orbits from visual observations of recovered meteorite falls, it is now preferable to use reliable orbits from the camera networks for fireballs which are believed to have dropped meteorites that could not be located, or, that are believed to have been physically identical to meteorites, although no appreciable mass survived the atmospheric flight. This paper will review current knowledge based on this approach to the problem.