Big Guns And Smoking Bullets

Nature has reported a 90% sure conclusion to the Great Dead Dinosaur Whodunit--

. An asteroid breakup 160 Myr ago as the.probable source of the K/T impactor

William F. Bottke¹, David Vokrouhlický^1,2 & David Nesvorný¹

The terrestrial and lunar cratering rate is often assumed to have been nearly constant over the past 3 Gyr. Different lines of evidence, however, suggest that the impact flux from kilometre-sized bodies increased by at least a factor of two over the long-term average during the past 100 Myr. Here we argue that this apparent surge was triggered by the catastrophic disruption of the parent body of the asteroid Baptistina, which we infer was a 170-km-diameter body (carbonaceous-chondrite-like) that broke up Myr ago in the inner main asteroid belt. Fragments produced by the collision were slowly delivered by dynamical processes to orbits where they could strike the terrestrial planets. We find that this asteroid shower is the most likely source (>90 per cent probability) of the Chicxulub impactor that produced the Cretaceous/Tertiary (K/T) mass extinction event 65 Myr ago.

Here's a piece of the lethal <<weapon
Found in 1998, and now entered into evidence -- this split-open  2.5 mm clay-encrusted bit of carbonaceous chondrite, found in a deep sea drill core, may indeed be a fragment of the Baptistina parent body  asteroid that gave rise to the meteor responsible for the Yucatan impact crater.

Here also is the Nature article's diagram of the post breakup orbital  pattern of the asteroidal buckshot  that turned the inner solar system into the shooting gallery we inhabit today