The flux of small near-Earth objects colliding with the Earth

• Published in: Nature (London) 2002-11, Vol.420 (6913), p.294-296
• Main Authors: Brown, P., Spalding, R. E., ReVelle, D. O., Tagliaferri, E., Worden, S. P.
• Format: Article
• Language: English
• Subjects: Asteroids; Astronomy; Atmosphere; Calibration; Disasters - statistics & numerical data; Earth; Earth (Planet); Earth, ocean, space; Energy; Exact sciences and technology; Explosions; Fluctuations; Humanities and Social Sciences; Interplanetary space; letter; Light; Meteoroids; Meteors, meteoroids and meteor streams; Minor Planets; Motion; multidisciplinary; Particle Size; Science; Science (multidisciplinary); Siberia; Solar system; Spacecraft; Temperature; Time Factors; Trees - physiology
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature01238

Asteroids with diameters smaller than ∼50–100 m that collide with the Earth usually do not hit the ground as a single body; rather, they detonate in the atmosphere 1 . These small objects can still cause considerable damage, such as occurred near Tunguska 2 , Siberia, in 1908. The flux of small bodies is poorly constrained, however, in part because ground-based observational searches pursue strategies that lead them preferentially to find larger objects 3 . A Tunguska-class event—the energy of which we take to be equivalent to 10 megatons of TNT—was previously estimated to occur every 200–300 years, with the largest annual airburst calculated to be ∼20 kilotons (kton) TNT equivalent (ref. 4 ). Here we report satellite records of bolide detonations in the atmosphere over the past 8.5 years. We find that the flux of objects in the 1–10-m size range has the same power-law distribution as bodies with diameters >50 m. From this we estimate that the Earth is hit on average annually by an object with ∼5 kton equivalent energy, and that Tunguska-like events occur about once every 1,000 years.