Scientists working in southern China have added to previous research that supports the idea that an asteroid or comet smacked the Earth 251 million years ago, causing the planet's worst ever mass extinction.
Kunio Kaiho from Tohoku University and his colleagues found tell-tale elements in rocks from that geological time frame, the end of the Permian Period.
The cause of the extinction at the end of the Permian Period was much debated until recently. Researchers
trapped inside special molecules, known as Buckyballs, in ancient soil layers. Scientists say the evidence pointed to a colossal whack from a comet or asteroid roughly 3.7 to 7.5 miles (6 to 12 kilometers) wide -- about the same size as the one that ultimately destroyed most dinosaurs 186 million years later. Now, Kaiho and his colleagues have found evidence of a planetary release of types of sulfur and strontium at the end of the Permian, along with a coincident concentration of mineral grains that appear to have been remelted due to an impact.
His team's discoveries at Meishan (Mei Mountain) suggest that an asteroid or a comet hit the ocean at the end of the Permian, triggered a rapid and massive release of sulfur from the mantle to the ocean-atmosphere system, swooped up a significant amount of oxygen, precipitated acid rain, and possibly set off large-scale volcanism.
"Understanding the cause of this event is important because it represents the largest mass extinction," Kaiho said, "and it led to the subsequent origination of recent biota on Earth."
| The Five Worst Extinctions |
| Click here for a list of the five most lethal extinctions on our planet. |
Kaiho discovered the significance of the site when he took samples from it in 1996 and again in 1998.
"We would like to clarify paleoenvironmental changes and causes of the end Permian mass extinction in different places and of the other mass extinctions which occurred during the past 500 million years: end Ordovician, Late Devonian, and end Triassic," he said.
The research was published in the September issue of Geology.
The extinction at the end of the Permian killed 95 percent of Earth's species, 53 percent of marine families and 70 percent of land species such as plants, insects and vertebrate animals. Because it was so effective at clearing out competition, this extinction is credited with paving the way for new lizards to walk the Earth -- lizards which evolved into dinosaurs.
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