The Chelyabinsk Super Bolide: Part II
When the space rock could no longer handle the intense pressure and heat the body exploded, the energy released was over four hundred and seventy kilotons of TNT! The explosion did cause damage and injuries, over 1,500 people were injured due to shattered glass. Countless other buildings were damaged, a garage door was blasted inwards, and even the roof of a building was collapsed in by this intense air burst of energy. The citizens of Chelyabinsk thought that they had possibly just been bombed by another country. Unfortunately, hardly anyone knew what really happened and that a powerful shock wave would soon be upon them. The sound wave took about eight to nine minutes to reach the ground and traveled for many miles. Even infrasound instruments, used to detect very low frequency explosion to monitor the testing of atomic bombs, detected the sound of this event as far away as Alaska! This asteroid impact was huge, the shot heard around the world, and the people of Chelyabinsk are extremely lucky for a number of reasons.
There could have been a new crater near or in the city of Chelyabinsk, people could have been killed by this space rock. A huge factor that played in their favor is that most asteroids are composed of silicate rocky elements. Most asteroids have also endured collisions with other asteroids during their time in space, this creates cracks and fractures within the rock. As the space rock was hurtling towards earth the intense heat entered these fractures causing the rock to explode. The angle of entry also plays a role in the destructiveness of an asteroid. Too shallow of an angel of entry and the space rock harmlessly bounces off the atmosphere. Too steep of an angel and the asteroid has less time to heat up and burn up completely or explode. Luckily the angle of entry for the Chelyabinsk asteroid was just right, giving enough time for the rock to heat up and explode. These important factors played a key role in saving the people of Chelyabinsk.
Once the event was over people took to the streets and nearby fields to look for meteorites! A recent snow fall made it very easy for people to find meteorites, all they had to do was look for holes in the snow. The meteorite was classified as an Ordinary Chondrite LL5. Ordinary Chondrites are the most common type of meteorite and the LL stands for very low free elemental iron and nickel. The number represents the type of alteration the rock was subjected to during its lifetime in space. Numbers 1 and 2 represent water aqueous transformations, 3 represents unaltered pristine meteorites, and 4-7 represents thermal transformations. As a 5 the Chelyabinsk asteroid underwent a significant thermal transformation. As expected the meteorites recovered and sliced opened had fractures and melt veins where heat from the fall entered and melted the rock. Some of the meteorites were composed entirely of melt material! This event was a once in a lifetime occurrence, we hope, and luckily this space invader was small enough for our atmosphere to stop it from doing much more damage. The people of Chelyabinsk will never forget this rare interaction with space.