Last December, Earth received a Christmas present that we were not even aware of. The second most powerful asteroid detonation of the last 30 years was caused on 18 December by the explosion of a bolide over the Bering Sea. The explosion was estimated at 173 kt – about 11.5 times more powerful than the atomic bomb dropped on Hiroshima, and more than enough to guarantee a really painful day to anything unlucky enough to reach it.
The explosion has so far failed, as it hit an uninhabited area of the Russian Kamchatka Peninsula. He was photographed in the Earth 's atmosphere by the Japanese Himawari satellite.
Some color views of #meteor which flew over the North Pacific in December 2018, taken by Japan #Himawari Satellite.
The meteor is really clear here – bright orange fireball on the blue + white background!
Background: https://t.co/r403SQxicZ pic.twitter.com/ctNN8zxsXb
– Simon Proud (@simon_sat) March 18, 2019
The fact that we missed this rock testifies to our rather incomplete image of the space around the Earth, as well as the difficulty of following rather small space rocks. The BBC reports that it will take another 30 years for NASA to map all asteroids up to 140 meters in size near Earth. There is no chance that a rock of this size will cause an extinction event, but the impact on a region can be significant.
The Tunguska event, July 30, 1908, illustrates the importance of tracking meteors, even the smallest ones. That day, an explosion in the Siberian taiga destroyed some 2,000 square kilometers of forest, after the probable explosion by a meteor. The Tunguska impactor would be only 60 to 190 meters wide (the broad estimates reflect uncertainty as to whether it was an icy or rocky body).
The car on December 18 was much smaller (just a few meters) and exploded 25.6 km above the surface of the Earth, and not on the 5 to 10 km traveled by Tunguska. The most modern estimates of its explosive force place it at 3 to 5 megatonnes of TNT, which easily matches the explosive power of modern nuclear weapons. No known asteroid is on a collision course with the Earth, but such close encounters are a disturbing reminder that the rocks are there.
The good news is that on the galactic time scales, there is a lot less rocks there than before. Jupiter may have done us a huge favor by sweeping away the debris of the solar system at the beginning of our own story. The so – called last – minute heavy bombardment may have done a lot of damage to our planet as well as to Mars, but the decline in the number of massive impact events over the billions of years has allowed life to flourish. It is estimated that 100 km of rocks were hammered early in its history. To put this into perspective, the impactor Chicxulub would have been between 11 and 80 km. Life on Earth would, we say, be deeply disturbed if the local neighbors had not calmed down and stopped throwing stones.