Extraterrestrial Impact Preceded Ancient Global Warming Event

A comet strike may have triggered the Paleocene-Eocene Thermal Maximum (PETM), a rapid warming of Earth caused by an accumulation of atmospheric carbon dioxide 56 million years ago, which offers analogs to global warming today.

Sorting through samples of sediment from the time period, researchers at Rensselaer Polytechnic Institute discovered evidence of the strike in the form of microtektites -- tiny dark glassy spheres typically formed by extraterrestrial impacts.  The research will be published in the journal Science.

"This tells us that there was an extraterrestrial impact at the time this sediment was deposited -- a space rock hit the planet," said Morgan Schaller, an assistant professor of earth and environmental sciences at Rensselaer, and corresponding author of the paper.  "The coincidence of an impact with a major climate change is nothing short of remarkable."  Schaller is joined in the research by Rensselaer professor Miriam Katz and graduate student Megan Fung, James Wright of Rutgers University, and Dennis Kent of Columbia University.
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Atmospheric carbon dioxide increased rapidly during the PETM, and an accompanying spike in global temperatures of about 5 to 8 degrees Celsius lasted for about 150,000 years.  Although this much is known, the source of the carbon dioxide had not been determined, and little is known about the exact sequence of events -- such as how rapidly carbon dioxide entered the atmosphere, how quickly and at what rate temperatures began to rise, and how long it took to reach a global high temperature.

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