• Question: How many times have space rocks ( asteroids ) crashed into the Earth?

    Asked by zgrafitipig to Carol, Ellie, John, Philip, Rebecca on 2 Jul 2012.
    • Photo: Rebecca Lacey

      Rebecca Lacey answered on 2 Jul 2012:

      Little objects, such as small asteroids, frequently collide with the Earth. Large asteroids (bigger than 1km in diameter) hit the Earth around every 500,000 years. Bigger collisions with asteroids bigger than 5km in diameter (that’s massive!!) happen about once every million years!

      We don’t often hear about collisions because when the smaller asteroids enter the Earth’s atmosphere they burn up and are vaporised so nothing actually “hits” the Earth. Objects with diameters smaller than 10 m are called “meteoroids” (“meteorites” if they strike the ground). An estimated 500 meteorites reach the surface each year, but only 5 or 6 of these are typically recovered and made known to scientists.

    • Photo: Carol White

      Carol White answered on 2 Jul 2012:

      Loads and loads and loads and loads! Rebecca’s spot on, we don’t even notice most of them, especially as lots end up in the ocean!

      You’re not likely to be hit on the head by one!

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