A late Miocene dust shower from the break-up of an asteroid in the main belt

Throughout the history of the Solar System, Earth has been bombarded by interplanetary dust particles (IDPs), which are asteroid and comet fragments of diameter similar to 1-1,000 mu m. The IDP flux is believed to be in quasi-steady state: particles created by episodic main belt collisions or cometary fragmentation replace those removed by comminution, dynamical ejection, and planetary or solar impact. Because IDPs are rich in He-3, seafloor sediment He-3 concentrations provide a unique means of probing the major events that have affected the IDP flux and its source bodies over geological timescales(1-4). Here we report that collisional disruption of the >150-km-diameter asteroid that created the Veritas family 8.3 +/- 0.5 Myr ago(5) also produced a transient increase in the flux of interplanetary dust-derived He-3. The increase began at 8.2 +/- 0.1 Myr ago, reached a maximum of similar to 4 times pre-event levels, and dissipated over similar to 1.5 Myr. The terrestrial IDP accretion rate was overwhelmingly dominated by Veritas family fragments during the late Miocene. No other event of this magnitude over the past similar to 10(8) yr has been deduced from main belt asteroid orbits. One remarkably similar event is present in the He-3 record 35 Myr ago, but its origin by comet shower(1) or asteroid collision(6) remains uncertain.