[Hill]

What connection does Chicxulub, the dinosaur-killer crater in Mexico's Yucatan, have with Tycho, the most prominent lunar crater viewable from Earth? And what do they both have to do with an obscure object from the asteroid belt object called Baptistina?

Using simulations, a team of researchers investigated the possible results of a collision between two members of the asteroid belt, which produced many smaller fragments .

The gradual spreading of the family caused many fragments to drift into a nearby "dynamical superhighway" where they could escape the main asteroid belt and be delivered to orbits that cross Earth’s path. The team's computations suggest that about 20 percent of the surviving multi-kilometer-sized fragments in the Baptistina family were lost in this fashion, with about 2 percent of those objects going on to strike the Earth, a pronounced increase in the number of large asteroids striking Earth.
Support for these conclusions comes from the impact history of the Earth and Moon, both of which show evidence of a two-fold increase in the formation rate of large craters over the last 100 to 150 million years. As described by Nesvorny, "The Baptistina bombardment produced a prolonged surge in the impact flux that peaked roughly 100 million years ago. This matches up pretty well with what is known about the impact record."
Bottke adds, "We are in the tail end of this shower now. Our simulations suggest that about 20 percent of the present-day, near-Earth asteroid population can be traced back to the Baptistina family."

Research by Dr. William F. Bottke, Dr. David Vokrouhlicky and Dr. David Nesvorny suggests that the impactor believed to have wiped out the dinosaurs and other life forms on Earth 65 million years ago can been traced back to a breakup event in the main asteroid belt. (Credit: Art by Don Davis)

Source: ScienceDaily: Large Asteroid Breakup May Have Caused Mass Extinction On Earth 65 Million Years Ago
Source: Killer Collision: Dino demise traces to asteroid-family breakup: Science News Online, Sept. 8, 2007