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TORONTO — The asteroid that smacked into Earth and is believed to have wiped out the dinosaurs 65 million years ago may have originated in an enormous collision between two asteroids about 100 million years earlier, researchers argue in a paper to be published tomorrow in the influential journal Nature.
Professor William Bottke, assistant director of Space Studies at the Southwest Research Institute in Boulder, Col., and colleagues are more than 90 per cent sure that the breakup of a massive asteroid about 170 kilometres in diameter within the innermost region of the Main Asteroid Belt, which lies between Mars and Jupiter, created what is now known as the Baptistina asteroid family.
They argue that a chunk of this asteroid 10 kilometres in diameter made its way through the solar system and smashed into Earth millions of years later, creating the Chicxulub crater on the Yucatan Peninsula in Mexico.
That impact is believed to have caused the extinction of the dinosaurs.
“It shows that events that happen far away from the Earth can still have a significant influence on essentially the biological evolution, and, to some degree, the geological evolution of the planet,” Dr. Bottke told The Globe and Mail.
The researchers studied the asteroid cluster called the Baptistina asteroid family, which is made of asteroids of similar composition and orbital geometry. Using computer simulations, they were able to re-trace the orbits of the asteroids back to their initial parent stage.
They determined that the parent 170-kilometre-wide asteroid was struck head-on by another asteroid 60 kilometres in diameter.
“If you look at how far the asteroids have travelled, you can use that distance like a clock to tell you how hold the break-up is,” Dr. Bottke said.
The researchers also studied the origins of the Chicxulub crater and determined that its composition – carbonaceous chondrite – matched what they believe to be what makes up the Baptistina asteroid family.
Dr. Bottke said there is also a 70-per-cent probability that the lunar crater Tycho, 85 kilometres in diameter and formed 108 million years ago, was formed by a Baptistina asteroid.
“We thought, ‘Gee, this breakup is going to produce a lot of fragments; a lot of them are going to escape and are going to get into the inner solar system',” he said.
“It's very possible this has really influenced the impact record on the Earth and moon and other planets in the inner solar system.”
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