Friday, July 1, 2022

The mineralogy of the rocks determines how deadly a meteorite impact is

Size doesn’t matter!

A multidisciplinary research team from the University of Liverpool and the Instituto Tecnológico y de Energías Renovables, Tenerife, have explored why some meteorites have caused mass extinctions. They found that the deadliness of a meteorite impact depends on the rock composition.

Meteorites have bombarded the earth throughout its long history. Scientists analyzed 44 impacts over the past 600 million years. For this, they used a new method: assessing the mineral content of the dust ejected into the atmosphere upon impact.

They found that meteorites hitting rocks rich in potassium feldspar always correspond with a mass extinction episode, irrespective of size.

Potassium feldspar is a powerful ice-nucleating mineral aerosol that strongly affects cloud dynamics, letting them through more solar radiation. This, in turn, warms up the planet and changes the climate. The atmosphere also becomes more sensitive to warming from greenhouse gas emissions, such as significant volcanic eruptions.

Liverpool sedimentologist Dr. Chris Stevenson from the University’s School of Earth, Ocean and Ecological Sciences said, “For decades, scientists have puzzled over why some meteorites cause mass extinctions, and others, even really big ones, don’t. It’s surprising when we put together the data: life carried on as normal during the 4th 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.”

“Many kill mechanisms have been proposed, such as large volcanic eruptions, but just like meteorites, these don’t always correlate with mass extinctions.”

“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.”

The study includes paleontology, asteroid stratigraphy, mineralogy, cloud microphysics, and climate modeling.

Dr. Stevenson said“This opens up a whole new avenue of research: what exactly kills off life during these episodes, and how long do the potassium feldspar effects last? Until now, only meteorites have changed the aerosol regime of the climate. However, present-day human activities represent a similar mechanism with increasing emissions of mineral aerosols into the atmosphere.”

Journal Reference:

  1. Pankhurst, M.J. et al. Meteorites that produce K-feldspar-rich ejecta blankets correspond to mass extinctions. DOI: 10.1144/jgs2021-055
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