Asteroid Broke Up, and Then it Killed the Dinosaurs

It was a controversial theory when first proposed years ago, but now most paleontologists side with the theory that a large asteroid strike 65 million years ago delivered the killing blow that wiped the dinosaurs off the Earth. Astronomers have traced back what they think was its parent object, which struck another asteroid millions of years ago, creating many large fragments. Fragments that went on to devastate the Earth, and pummel the Moon.

The researchers include Dr. William Bottke and Dr. David Nesvorny from the Southwest Research Institute, and Dr. David Vokrouhlicky from the Charles University in the Prague. Their article, entitled An asteroid breakup 160 Myr ago as the probable source of the K/T impactor, is published in this week’s issue of the Journal Nature.

Asteroid 298 Baptistina was originally an asteroid 170 km in diameter, residing in the innermost region of the asteroid belt when it was struck by another asteroid 60 km across. This impact created the Baptistina family, and originally contained 300 objects larger than 10 km, and 140,000 objects larger than 1 km.

Over time, sunlight heated the asteroids caused them to slowly change orbits, drifting away from the original impact orbit. And this is how the scientists pieced everything together. They calculated how the orbits would change over time, and then traced the objects back until the were at the same point. This was 160 million years ago, before the Baptistina breakup.

Many of these objects were put into an orbit that would eventually intersect with the Earth. The team calculated that the rise in impacts over the last 100 to 150 million years was due to this collection. Fortunately we’re now at the tail end of it. Dr. William Bottke noted, “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.”

How does this connect to the dinosaurs? The asteroid that killed them was thought to have impacted 65 million years ago, carving out a chunk of the Yucatan peninsula. Fragments and sediments recovered from the impact site match the chemical composition of the Baptistina family. Researchers think there’s a 90% match between the two.

One of the most prominent craters on the Moon, Tycho, was probably created by one of these fragments as well. The 85 km crater was carved out 108 million years ago. Of course, nobody has actually measured the rocks in this region to know for sure. That’ll take a return visit of humans going to the Moon.

Original Source: SwRI News Release