Do small meteorites kill more than big ones?

Why do some meteorites cause mass extinctions and others, even bigger, right? The question has been intriguing scientists for decades, but a study carried out by researchers from the University of Liverpool and the Institute of Technology and Renewable Energies, in Tenerife, could finally have found an answer. And it is that, as scientists explain in an article published in the ‘Journal of the Geological Society’ of London, when we talk about meteorites, size does not matter, or at least not as much as its mineral composition.

meteorites

Throughout its long history, Earth has been hit thousands of times by space rocks of all sizes. And when those rocks are big enough, the dust generated during the impact can completely darken the planet’s atmosphere, causing severe changes in climate and the disappearance of significant percentages of living species. But it’s not always like this.

The team of researchers, made up of paleontologists, experts in asteroids, mineralogy, cloud physics and climate modeling, tried to find out why meteorites such as Chicxulubwhose impact ended the age of the dinosaurs and 75% of the planet’s species, was much more lethal than many larger ones that did not cause any extinction.

To do this, the researchers analyzed 44 large impacts that occurred during the last 600 million years. And they did it using a totally new method, evaluating the mineral content of the dust expelled into the atmosphere at the moment of impact. In this way, they realized that meteorites that collide with rocks rich in potassium feldspara fairly common mineral, always cause mass extinction events, regardless of their size.

Greenhouse effect

Potassium feldspar is not toxic, but it is a powerful mineral spray that affects the dynamics of clouds, causing them to let in more solar radiation. This, in turn, warms the planet and changes the climate. The atmosphere also becomes more sensitive to warming from greenhouse gas emissions, such as large volcanic eruptions.

For Chris Stevenson, co-author of the study, “For decades, scientists have wondered why some meteorites cause mass extinctions and others, even really big ones, don’t. It is surprising when we put the data together: for example, life developed normally during the fourth largest known impact, with a crater 48 km in diameter, while an impact half that size is associated with a mass extinction only 5 years ago. millions of years”.

According to the researcher “Many deadly mechanisms have been proposed, such as large volcanic eruptions, but as with meteorites, these are not always linked to mass extinctions. Using this new method to assess the mineral content of meteorite ejecta layers, we show that every time a meteorite, large or small, strikes rocks rich in potassium feldspar, a mass extinction event occurs.”.

These surprising results open new avenues of research. What exactly kills the species during these episodes and how long can the effects of potassium feldspar last? Until now, only meteorites had been capable of altering the aerosol regime in the atmosphere, with serious consequences for the climate. “But now Stevenson concludes. the human activities present represent a similar mechanism with increasing emissions of mineral aerosols into the atmosphere». A valuable clue for future research.

Font: Jose Manuel Nieves / ABC

Reference article: https://www.abc.es/ciencia/abci-small-meteorite-can-kill-larger-202201030956_noticia.html