Narrative Report on the Hazard to Civilization Due to Fireballs and Comets

摘要

The 100,000 year average interval between asteroid strikes (Chapman & Morrison 1994) first became apparent during the 1970s. Another discovery of considerable moment about this time was that of object Chiron. Considered to be a 'giant comet' and found to be moving in a chaotic orbit beyond Saturn close to the ecliptic (Kowal l979,Oikawa & Everhart 1978), the possibility of its future transfer to a more stable sub-Jovian orbit capable of penetrating near-Earth space and hence threatening the Earth was also soon recognized (Bailey et al 1994, Steel et al 1994). The report then is by way of being a flier delineating the current state of research (historical and scientific) concerning the cometary and fireball threat.