The composition of a meteorite can make it more deadly

When predicting how deadly a meteorite impact on Earth could be, it makes sense that this estimate would be based on the size of the debris itself. This is not the case, however, according to a new study from the University of Liverpool. Instead, the researchers found that the deadliness of a meteorite can be determined by the composition of the rocks that it has struck along its way.

The key reason for this is the production of atmospheric dust. It is commonly known that ancient meteorite impacts have triggered mass extinctions throughout Earth’s history, and one of the contributing factors was the dust that covered the planet’s surface and atmosphere.

However, not all meteorites have caused such extinctions, and some of the smaller ones have been more lethal than larger ones. In order to understand this, a team of paleontologists, asteroid specialists, mineralogists, cloud microphysicists, and climate modelers set out to analyze 44 meteorite impacts over the last 600 million years. The experts examined the mineral content of the dust clouds that were created upon impact.

“For decades scientists have puzzled over why some meteorites cause mass extinctions, and others, even really big ones, don’t,” explained study co-author Dr. Chris Stevenson. “It’s surprising when we put together the data: life carried on as normal during the fourth largest impact with a crater diameter of ~48 km, whereas an impact half the size was associated with a mass extinction only 5 million years ago.”

Ultimately, it was discovered that all meteorites that resulted in widespread extinction had collided with rocks rich in potassium feldspar. While this mineral is common and benign, it is a powerful ice-nucleating mineral aerosol that has a dramatic effect on the dynamics of clouds, reducing their ability to protect the Earth from solar radiation. This ultimately heated the planet, changed the climate, and increased atmospheric sensitivity to emissions such as those tied to volcanic eruptions. 

“Using this new method for assessing the mineral content of the meteorite ejecta blankets, we show that every time a meteorite, big or small, hits rocks rich in potassium feldspar it correlates with a mass extinction event,” explained Stevenson. This means that meteorites impacting with potassium feldspar can be lethal to the planet Earth, regardless of the size of the meteorite.

The research findings have been published in the Journal of the Geological Society of London.

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By Calum Vaughan, Earth.com Staff Writer