Comet-impact may not have killed mammoths: Experts
London: The theory that a space impact was responsible for extinction of at least 17 groups of large animals including mammoths and great bears, can be discounted, claims a new study.
An asteroid or a comet strike was seen as the reason behind killing of giant bears, big cats, mammoths and the like, but tiny diamonds apparently created in the collision have been misinterpreted, a US-UK team says.
These 12,900-year-old sediments were claimed to hold exotic materials: tiny carbon spheres, ultra-small specks of diamond - called nanodiamond - and amounts of the rare element iridium that are too high to have occurred naturally on Earth.
These nano-sized, hexagonal bits of diamond, called lonsdaleite, can be good tracers for impacts; they’re created in the intense pressure and heat of a space collision.
But having examined closely the carbon spherules purported to contain nanodiamonds in this case, Tyrone Daulton, Nicholas Pinter and Andrew Scott said that they couldn’t find them, and that they were just "aggregations of carbon."
However, proponents of the impact theory are not prepared to let go of their ideas just yet, however.
"They looked at charcoal but we never mentioned that we ever found diamonds in the charcoal," BBC News quoted geoscience consultant Allen West, as saying.
"They did say that they looked in some carbon spherules but we looked at 10-15 per layer and specified that in our methodology, and they only looked at ``one to several`` - that’s their quote. They didn’t understand what they were supposed to be looking for," he added.
West said further nanodiamond evidence in support of the impact theory would be published in the coming weeks.
The study is published in the journal PNAS.
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