Planetary science: Killer asteroid shower identified
The catastrophic breakup of an asteroid 160 million years ago produced a shower of debris that was the most likely source of the impact event at the Cretaceous/Tertiary (K/T) boundary. This breakup took place in the inner asteroid belt of the Solar System, and is thought to have doubled for a while the number of impacts occurring on the terrestrial planets. A fragment from the breakup that eventually struck Earth is widely believed to have caused the mass extinction at the end of the Cretaceous period — the largest in 250 million years.

Several recent studies have noted an increase in the number of asteroid impacts in recent geologic history — the impact ‘flux’ has at least doubled over the last 100–200 million years. William Bottke and colleagues used computer simulations to show that this surge was probably triggered by the catastrophic disruption of a 170-km-diameter asteroid about 160 million years ago. This breakup produced a cluster of fragments known as the Baptistina asteroid family. By combining their numerical results with meteoritic constraints, they conclude that this asteroid shower is over 90% likely to be the source of the K/T impactor.

The authors suggest that the K/T event was part of a much larger process, occurring throughout the inner Solar System that may have created the Tycho crater on the Moon and many large craters on Venus and Mars. The breakup event is also likely to be the source of roughly one-third of present-day near-Earth objects.

CONTACT

William Bottke (Southwest Research Institute, Boulder, CO, USA)
Tel: +1 303 546 6066; E-mail: bottke@boulder.swri.edu

Philippe Claeys (Vrije Universiteit Brussel, Belgium) N&V author

E-mail: phclaeys@vub.ac.be