Tiny spherical droplets of glass found near the New Jersey coast might be evidence that a comet struck earth more than 55 million years ago, beginning a warming period that scientists say is the closest parallel to today's human-induced climate change.
Those are the findings of a new study in the leading journal Science, and appear to lend further credence to the hypothesis that the impact from an extraterrestrial object caused the warm period known as the Paleocene-Eocene Thermal Maximum, or PETM.
"That really raises the possibility and probability that there was indeed, first of all, an impact very closely coinciding with this Paleocene-Eocene Thermal Maximum," said Dennis Kent, a researcher at Columbia University's Lamont-Doherty Earth Observatory and Rutgers University and co-author of the paper.
Kent has previously argued that a comet might have caused the PETM, but the hypothesis didn't stick. In a 2003 paper, Kent said that magnetized particles found in New Jersey's clay might have resulted from a cometary collision. Some colleagues rejected that conclusion.
"Understandably, there was skepticism. Any time you propose kind of a dramatic event, that's sort of a natural reaction," Kent said. "But this adds a much more direct indication that there had to be something highly energetic to melt all that glass."
The glass was found in drill cores taken in Millville, Wilson Lake and Medford, New Jersey, by the paper's lead author, Morgan Schaller of Rensselaer Polytechnic Institute and his student Megan Fung. The tiny spherical droplets are known as "microtektites," and are formed from molten material that is ejected from an impact crater before cooling and falling back to earth.
But just because the glass was found on the Jersey coast doesn't necessarily mean that was where the comet landed. "It could have been next door, or it could have been on the other side of the planet," Schaller said.
The study raises questions about the massive release of carbon that caused the PETM. Many scientists have suggested that it took 5,000 to 20,000 years for that carbon to be released into the atmosphere. The carbon emissions in the PETM are the closest analogue scientists have found to current anthropogenic climate change, but high levels of carbon are currently entering the atmosphere at a much faster rate, making today's situation seem unprecedented.
However, Kent says a comet-induced ejection of carbon into the atmosphere could mean that the PETM works as a good analogy to what's happening with climate change today.
Many single-celled, ocean-dwelling organisms went extinct during the PETM, but other species like primates were able to move toward the earth's poles and quickly evolve during the period. But scientists have warned that today's carbon emissions far outpace those of the PETM, and that life forms might not have as long to adapt.