Scientists reveal new method of detecting past comet strikes upon Earth

Washington, December 14 (ANI): An investigation by scientists at the University of Kansas (KU) has revealed a promising new method of detecting past comet strikes upon Earth and gauging their frequency.

"Comet impacts might be much more frequent than we expect," said Adrian Melott, professor of physics and astronomy at the University of Kansas.

"There's a lot of interest in the rate of impact events upon the Earth. We really don't know the rate very well because most craters end up being destroyed by erosion or the comets go into the ocean and we don't know that they're there. We really don't have a good handle on the rate of impacts on the Earth," he added.

An investigation by Melott and colleagues reveals a promising new method of detecting past comet strikes upon Earth and gauging their frequency.

The research shows a potential signature of nitrate and ammonia that can be found in ice cores corresponding to suspected impacts.

Although high nitrate levels previously have been tied to space impacts, scientists have never before seen atmospheric ammonia spikes as indicators of space impacts with our planet.

"Now we have a possible new marker for extraterrestrial events in ice," Melott said. "You don't just look for nitrates, you also look for ammonia," he added.

Melott studied two possible cometary airbursts with Brian Thomas, assistant professor of physics and astronomy at Washburn University, Gisela Dreschhoff, KU adjunct associate professor of physics and astronomy, and Carey Johnson, KU professor of chemistry.

Melott and fellow researchers examined data from ice cores extracted in Greenland to compare atmospheric chemistry during the Tunguska and Younger Dryas events.

In both instances, Melott's group found evidence that the Haber process - whereby a nitrogen fixation reaction produces ammonia - may have occurred on a large scale.

"A comet entering the atmosphere makes a big shock wave with high pressure - 6,000 times the pressure of air," said Melott.

According to Melott, "It can be shown that under those conditions you can make ammonia. Plus the Tunguska comet, or some fragments of it, landed in a swamp. And any Younger Dryas comet presumably hit an ice sheet, or at least part of it did. So there should have been lots of water around for this Haber process to work."

"We think the simplest way to explain the signal in both objects is the Haber process. Comets hit the atmosphere in the presence of a lot of water and you get both nitrate and ammonia, which is what both ice cores show," he said. (ANI)