Dinosaurs Come, Dinosaurs Go
(From the May/June 2001 issue of StarDate magazine)
The reign of the dinosaurs ended 65 million years ago, perhaps after a large comet or asteroid slammed into Earth, drastically altering our planet’s climate and killing off most species of life. But in a grand bit of cosmic irony, a similar impact may have cleared the way for the rise of the dinosaurs.
Scientists have known for a while that something killed most of the life on Earth 250 million years ago. They suspect the trigger was the impact of an asteroid about the same size as the one that supposedly killed the dinosaurs.
A team of scientists led by Luann Becker of the University of Washington has found evidence to support that theory. The scientists found complex carbon molecules called buckminsterfullerenes, or Buckyballs, inside sediments deposited 250 million years ago in present-day China, Japan, and Hungary. The molecules contained helium-3, a form of helium gas that’s found in space, but rarely on Earth.
The carbon molecules probably arrived inside a comet or asteroid several miles in diameter. When it struck Earth’s surface, it blasted billions of tons of debris into the air, blocking sunlight and triggering drastic climate changes. This debris settled over much of the globe, forming a thin layer of sediments that marked the geological boundary between the Permian and Triassic periods. During the several thousand years after the impact, about 90 percent of all species of ocean life perished, along with 70 percent of land vertebrates.
This environmental cataclysm cleared the way for the rise of the dinosaurs. They reigned until the next great cataclysm 200 million years later. — Damond Benningfield
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