Blast from the past

UCSB researcher blames meteors for massive extinctions of earlier life.

By David Downs
South Coast Beacon

Nothing spells extinction quite like a giant asteroid.

Scientists have long theorized that a massive space rock slammed into Earth and did in the dinosaurs 65 million years ago. But new evidence from UCSB researcher Luann Becker published in November credits colossal cosmic carnage with even bigger extinctions.

The “Great Dying” of 251 million B.C. killed many more species than the famed dinosaur die-out, and Becker claims to have found hard evidence that a meteor did the deed.

“Most scientists agree that one such impact did in the dinosaurs, but evidence for large collisions coincident with other mass extinctions remained elusive until recently,” Becker stated. “Researchers are now discovering hints of ancient impacts at sites marking history’s top five mass extinctions, the worst of which eliminated 90 percent of all living species.”

Working on the Central Transantarctic Mountains in Antarctica, Becker and other team members drilled up soil samples dating to the period of the deaths. Among the dirt is several meteoric fragments and shocked quartz — a rare form of the earth rock created by asteroid impacts.

The evidence syncs up with core samples from other continents, which makes sense because Earth had a single, big continent during the time of the collision.

Curiously, Becker’s samples lacked iridium — a mineral rare to Earth, but abundant in space rocks. Iridium is a cosmic calling card that helped scientists cobble together their first impact theory of dinosaur extinction.

Doug Burbank, director of the Institute for Crustal Studies, said the lack of iridium is interesting, but doesn’t debunk Becker’s work. Soil samples accrue and get mixed together over eons, he said. An impact is a relative flash in the pan.

“Soils have complex origins and they integrate a lot of time. It’s something that gets churned and mixed, so I wouldn’t be too surprised if it wasn’t showing very apparent traces,” he said.

Becker and other team members will continue to search for more hard evidence in rocks dating to the end of the Permian era and the beginning of the Triassic.

Becker said about 60 meteorites three miles wide or larger have hit the planet in the past 600 million years. The smallest ones would have punched holes in the Earth more than 60 miles wide with countless thousands of square miles of devastation.

According to NASA statements, there are currently 1,200 near-Earth asteroids capable of doing similar damage, and millions of smaller ones like the 200-foot Tungunska asteroid of 1908. It flattened 800 square miles of forest.