»In which the evidence presents itself

An article in the San Francisco Chronicle reports:

On Thursday, in the journal Nature, a group headed by William F. Bottke, an asteroid expert at the Southwest Research Institute in Boulder, Colo., traces that impact back to a giant asteroid named Baptistina nearly 100 miles in diameter. Baptistina, the team of scientists say, was rammed by another, unnamed asteroid at least 35 miles in diameter in a violent collision about 160 million years ago - give or take 20 million years. The collision showered nearby space with at least 300 fragments bigger than 20 miles in diameter and more than 140,000 smaller asteroids, each one more than 3 miles around, Bottke contends. The smaller asteroids are now known as the Baptistina family, and according to Bottke and his colleagues - David Vokrouhlicky of Chares University in Prague and David Nesvorny of Bottke's institute - it was one of those "refugees" from Baptistina that created the 110-mile-wide Chicxulub crater. Not only that, they say, it was another earlier Baptistina offshoot asteroid that crashed into the moon about 110 million years ago and gouged out the well-known lunar crater called Tycho, whose debris the Apollo 17 astronauts encountered on America's last manned flight to the moon 35 years ago.

The usual childhood fascination with dinosaurs took hold of me specifically in two ways: we lived quite near a natural-history museum with a massive dinosaur hall, and school trips frequently took us there to gape in awe at the forty-foot high (or long) skeletons; and in junior-high, my father and I heard the Doctors Alvarez, pere et fils, speak in a small lecture hall on the campus of the University of Pittsburgh. The notion that we could track an event so long ago through a combination of archaeology, palaeontology, astrophysics, and intuition staggered me.