Asteroids are unformed planets that orbit the sun. While an untold number of asteroids have hit Earth during its 4.5 billion year history, most are relatively small and have done little damage. 

For example, right now there are five asteroids that are hurtling close to Earth according to NASA. But don’t worry — the closest, “2021 LU8,” will come at least 1,258,507 kilometers from our planet, more than three times the distance between us and the moon. Even if it did make it, it’s not big enough to pose much threat.

How common are asteroids?

According to NASA, an asteroid about the size of a car enters our atmosphere once a year. Space rocks smaller than these, known as “meteors,” are constantly entering our atmosphere, but typically burn up upon entry. Those that make it usually land in the ocean or wilderness without anyone noticing. Much bigger asteroids are far rarer. An asteroid the size of a football field enters the atmosphere about once every 2,000 years, causing destruction where they land.

When was the last time a big asteroid hit earth? 

The last time a giant asteroid punched Earth was June 30, 1908, when a sudden explosion wiped out 2,000 square kilometers of wilderness in Tunguska, Russia, leaving a massive crater in the ground. The Tunguska explosion made history as the largest natural object to strike Earth in living memory. 

What about even bigger asteroids?

Miles-long asteroids are out there, but space is so vast they very rarely reach Earth. In fact, supersized asteroids like the one believed to have killed the dinosaurs —  an astounding 7-miles long — are so rare it’s been 66 million years since one hit our planet. 

What is International Asteroid Day (June 30)?

While asteroids don’t threaten us all that much, we still need to be ready for them. That’s why celebrating “International Asteroid Day,” held every June 30 in commemoration of the Tunguska explosion, is so important. The day was founded by the United Nations in 2016 to raise awareness about asteroids and the need to protect our planet from them. To learn more about asteroids and how we can prepare for them, visit the International Asteroid Day website.

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