Only asteroids that hit a certain mineral trigger a mass extinction

By Kerry Hebden

Throughout Earth’s history, our planet has been bombarded with countless number of meteorites, ranging in size from rock fragments that barely leave an imprint to huge kilometre-size boulders that wiped out huge swathes of life. But do all large impacts lead to mass extinctions? Perhaps not – as geologists have found that the mineral make-up of the rocks a meteorite hits matters just as much as its size.

Large impacts produce ejecta, in which huge amounts of dust is thrown into the atmosphere, blocking out the sun. …