Two asteroids collide, space rocks spew out, one kills dinosaurs

William Atkins
Thursday, 06 September 2007 08:01

Science - Space

In a nutshell, a new U.S. study states that two giant asteroids collided inside the asteroid belt about 160 million years ago, and two fragments hit the Earth and the Moon. Mass extinctions occurred on Earth, killing, among other creatures, the dinosaurs.          

Specifically, one of the fragments made it to Earth about 65 million years ago, crashed to form the 112-mile (180-kilometer) diameter Chicxulub crater near Mexico’s Yucatan Peninsula, and another hit the Moon, to make the 53-mile (85-kilometer) diameter Tycho crater.

The solar system’s main asteroid belt, a region between the planets Mars and Jupiter, contains hundreds of thousands of asteroids have been identified and millions of others are out there but still undetected.

According to the article (“An asteroid breakup 160 Myr ago as the probable source of the K/T impactor” [449, 48-53]) published in the Thursday, September 6, 2007 issue of the journal Nature, a 170-kilometer asteroid collided with a 60-kilometer asteroid.

William F. Bottke, David Vokrouhlicky, and David Nesvomy, authors of the study and astronomers at the Southwest Research Institute (Boulder, Colorado, U.S.A.), were studying the database from the Sloan Digital Sky Survey when they noticed a hole within a group of rocks called the Baptistina asteroid family. The vacant volume of space, they concluded, was due to the gravitational tug-of-war between Mars and Jupiter, which wiped the space clear of asteroids.

According to computer models, the asteroids, previously located in this volume, were sent into orbits that crossed the orbit of Earth and the Moon. Eventually two of them hit the Earth and the Moon. The astronomers retraced the history of the Baptistina asteroids and found that they were likely the result of a collision of these two asteroids about 160 million years ago.

Two of them left the family and collided with the Earth and the Moon about 65 million years ago, setting the stage for the collision that ended the Cretaceous Period (K) and began the Tertiary Period (T), what is called the Cretaceous-Tertiary extinction event. The asteroid that hit the Earth is called the K/T impactor. It is believed to have been least 6 miles (10 kilometers) in diameter before impact.

The Baptistina asteroid family is named after the largest member of the family, 298 Baptistina, which was discovered by French astronomer Auguste Charlois on September 9, 1890. It is still orbiting about the solar system. It is about 25 miles (40 kilometers) in diameter. The family, itself, consists of about 300 bodies that are larger than 6 miles (10 kilometers) in diameter and around 135,000 bodies that are larger than 0.6 miles (1 kilometer) in diameter.

The study by the astronomers does not necessarily mean that such a series of events actually happened. There is  evidence that the actions happened but further research is needed to substantiate their findings.