Over the last 4.5 billion years, Earth has been slammed with space rocks several times, seemingly at random.
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Those rogue space rocks have their own holiday: International Asteroid Day, celebrated on June 30.
It’s held on the anniversary of the Tunguska explosion, when part of an asteroid fell to Earth and disintegrated in a massive fireball over Siberia in 1908.
2. Captured here in false color is Gosses Bluff crater in Australia, which came into existence 140 million years ago.
1. The Ries Crater in Germany is a little hard to spot, since people have settled in its depression since medieval times. It was carved by an impact 15 million years ago.