Impact Earth: How have meteorites shaped our planet?

Discover how being bombarded by space rocks helped create the world as we know it

Today is Asteroid Day, an international day dedicated to sharing information about the world of asteroids. Created and run by the Asteroid Foundation, Luxembourg, events around the world will explore the roles of asteroids for future space travel and even Earth’s protection from impacts. Held on the 30 June each year, this day of asteroid exploration shares it’s date with the anniversary of the 1908 Tunguska impact, Russia. As one of many impact events, Earth sure hasn’t had it easy since it’s creation around four billion years ago.  

Throughout its life our planet has been repeatedly hit, pummelled and even shattered by incoming space rocks, at times wiping out vast swathes of life and significantly changing our planet’s habitability. But these mega impacts haven’t just caused mass extinctions; they’ve also been responsible for allowing life to thrive here in the first place, and our very own Moon may owe its existence to a colossal impact long ago.

Our Solar System is full of asteroids and comets, pieces of debris left over from the Sun’s infancy that failed to form into planets. Some of these orbit close to Earth and are known as near-Earth asteroids, the ones that make the closest passes to our world. The majority of asteroids in our Solar System can be found in the asteroid belt between Mars and Jupiter, home to millions of asteroids, with the largest being Vesta, which has a mean diameter of 530 kilometres. Farther out in the Solar System you’ll find Trojan asteroids, which share orbits with the larger planets, and in the outer Solar System, the Kuiper Belt and beyond you’ll find pieces of icy rock. Occasionally, a comet from out here makes its way towards Earth.

If one of these rocks gets set on a collision course with Earth the consequences for us can be dire. Most debris from the Solar System simply burns up in our atmosphere and causes us few problems, becoming what’s called a meteor. If they’re big enough, however, they can make it to the surface in the form of a meteorite. And the bigger a meteorite is, the bigger an impact it’ll have on our planet. We measure the impact an asteroid could have on our planet using the Torino Scale, which ranges from 0 to 10..

This article was originally published in How It Works issue 122, written by John O’Callaghan 

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