On 15 February 2013, an approximately 20-meter (66 feet) meteoroid^{Notes 1} entered Earth’s atmosphere over Russia, with a speed of 19.16 ± 0.15 kilometers per second (60,000-69,000 km/h or 40,000-42,900 mph). Its mass is estimated at 7,000 to 10,000 tons, one of the largest meteoroids entered Earth’s atmosphere in the recent history. Then, at 9:20 am local time (03:20 UTC), it exploded some 20 to 30 kilometers above the city of Chelyabinsk and created a gigantic fireball (known as a superbolide^{Notes 1}) brighter than the Sun. An estimated 500 kilotons of energy was released by the explosion. For a comparison, the “Little Boy”, the atomic bomb dropped on the Japanese city of Hiroshima on 6 August 1945 exploded with an energy of approximately 15 kilotons of TNT. So, the Chelyabinsk meteor’s explosion was about 33 times stronger. The shock waves damaged several thousand buildings and injured approximately 1,500 people. No deaths were reported.

Scientists estimate such events occur on average once every 100 years. The most well-known was the Tunguska event, which occurred near the Stony Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908. It is also the largest impact event on Earth in recorded history. Studies have yielded different estimates of the meteoroid’s size, on the order of 60 to 190 meters (200 to 620 feet), depending on whether the body was a comet or a denser asteroid.