Asteroids are rock-like objects that orbit the Sun, and meteors are pieces of asteroids (or comets) that enter the Earth's atmosphere. While small meteors occur every day, large meteors or asteroids are far rarer. According to NASA, a car-size asteroid enters our atmosphere about once a year, burning up as a fireball, while an object the size of a football field hits Earth roughly every 2,000 years, causing major damage.
Intrigued? Click through this gallery to discover some of the close calls from the last 20 years.