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Astrobiology:
Latest News
2001-09-06 | SCIENCE
Asteroid or Comet Caused Earth's Largest Mass Extinction
Scientists working in China have uncovered additional evidence that an asteroid or comet impact triggered the Permian-Triassic extinction. The mass extinction 251 million years ago was Earth's worst, wiping out perhaps 95 percent of all species on the planet. Recently, a team led by Dr. Luann Becker of the University of Washington examined molecules taken from soil layers from the end of the Permian period, and found that the buckyballs contained gases of extraterrestrial origin. Something must have brought these gases to Earth on the cusp of the Permian and Triassic periods—presumably, a comet or asteroid. Now researchers from Tohoku University in Japan, studying the Permian-Triassic boundary in Southern China, have unearthed sulfur and strontium that was apparently tossed skyward when the object struck. They have also identified mineral grains that appear to have melted from the heat of an impact. Among the few groups of animals to survive the Permian-Triassic extinction were reptiles known as archosaurs, the ancestors of the dinosaurs. The extinction was an important step toward the emergence of dinosaurs as the dominant life form. Understanding how events originating in space affect evolution is a significant focus of astrobiology.
Full text of original item
from Space.com, Sep 06, 2001
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(NASA) - The worst mass extinction in Earth's history may have been caused by an asteroid or comet impact.
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