Asteroid and Comet Bombardment of the Earth
Abstract
The history, probability, and physical and biological effects of asteroid and comet impacts on the earth are surveyed. Astronomical-survey data on earth-crossing asteroids and comets are presented and compared with theoretical models of impact cratering, geological-survey data on extant craters, and observations of lunar cratering to calculate the present and geological-time frequency distribution of the kinetic energy of colliding bodies. Data from historic-collision observations and prehistoric-collision geological studies are used to classify small craters from iron meteorites, large young craters, ancient Phanerozoic impact structures, and large Precambrian impact structures. The transient effects of projectiles of 5-km or larger diameter on global climate are considered capable of causing the extinction of species in some environments, and dozens of such impacts are estimated to have occurred during the Phanerozoic. Precambrian life was probably subjected to the effects of several 20-30-km projectiles and a higher overall collision rate.
- Publication:
-
Annual Review of Earth and Planetary Sciences
- Pub Date:
- 1983
- DOI:
- 10.1146/annurev.ea.11.050183.002333
- Bibcode:
- 1983AREPS..11..461S
- Keywords:
-
- Asteroids;
- Comets;
- Cratering;
- Earth Surface;
- Impact Damage;
- Planetary Craters;
- Biological Effects;
- Iron Meteorites;
- Precambrian Period;
- EARTH;
- ASTEROIDS;
- COMETS;
- BOMBARDMENT;
- IMPACTS;
- EARTH-CROSSERS;
- FLUX;
- COLLISIONS;
- GEOLOGY;
- HISTORY