Ordinary-Chondrite Abundances in Different Mass Ranges

The number ratio of carbonaceous to ordinary chondrites (the CC/OC ratio) is mass dependent. It is somewhat high for large meteorites (0.20), very high for the largest fireball-producing meteoroids (30), low for most meteorite falls (0.04-0.05), and extremely high for micrometeorites (86) and interplanetary dust particles (IDPs) (>>100). The high CC/OC ratio among small particles reflects the predominance of C asteroids beyond 3 AU; these particles spiral into the Inner Solar System (and reach the Earth) via the Poynting-Robertson effect. The high CC/OC ratio among large objects results from the seasonal Yarkovsky effect, which transfers asteroids (mainly the abundant C asteroids from the Outer Solar System) into Near-Earth Asteroid (NEA) orbits.