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Falling from the sky

By Pat, 21 February 2013 News

Satellite image showing the vapour trail.

The white dot in the centre of the image is the vapour trail caused by the meteor.
Image: European Space Agency

A meteor caused quite a stir near Chelyabinsk in central Russia last week. While countless tiny meteors fly across Earth’s sky every day, this particular ‘shooting star’ was much more spectacular – video footage of the event shows a fireball streaking across the sky before exploding.

Most meteors don’t cause much damage but this one exploded with a force many times more powerful than an atomic bomb. The shockwave caused by the explosion damaged buildings and shattered windows. Many people were injured by the blast, mainly from broken glass.

Many meteors start out as asteroids. Asteroids are bodies made of minerals and metals that orbit the sun, but are too small to be considered planets. They range in size, with the largest being hundreds of kilometres wide.

NASA estimates that as it hit the atmosphere, the meteor was about 17 metres across and weighed 10 000 tons. The reason that this event wasn’t predicted was that the asteroid was too small and dark to be detected – yet it still packed quite a punch!

In relation to the Earth, asteroids can be zipping by at high speeds through the vacuum of space. When an asteroid’s orbit comes close to that of a planet, such as the Earth, the planet’s stronger gravitational attraction pulls the asteroid towards it. When it hits the atmosphere, it is called a meteor.

Friction with the Earth’s air heats the meteor, making it so hot that the rock starts to burn up. If you look up into the night sky, you might see shooting stars – these are objects burning up as they enter the Earth’s atmosphere. Most meteors disintegrate into dust and gas. Some break into pieces that can still strike the ground, where they can be found as meteorites.

Large meteorites have crashed into the Earth before. The most common theory explaining the extinction of the dinosaurs points to a huge meteorite that hit the region around Mexico. Such events have the power to dramatically alter the Earth’s environment on a global scale. So while the Chelyabinsk meteor might have been small fry in cosmic terms, it is still a reminder of the potential impact that asteroids might have on our planet.

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