When a huge meteor plowed through the sky over Chelyabinsk, Russia Friday morning, it punched a 6m-wide hole in the ice at Lake Chebarkul, about 80 km west of the city. Expecting to find a large meteorite fragment there, divers scouring the mud at the bottom of the lake for three hours, but reported that nothing was found. The only pieces that were found were small, roughly 1 cm wide fragments around the edge of the hole.
So, what happened? How did such a large hole get punched in the ice if there wasn't something equally large to create it?
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It's difficult to know for sure without more evidence, but just from the photos and video of the meteor trail, it's unlikely that anything big survived to reach Lake Chebarkul. The vapour trail was reduced to almost nothing, shortly after the meteor exploded. If anything large survived, it would have maintained a larger vapour trail as it continued along the meteor's path.
The answer probably lies in the shock wave that the meteor generated as it flew through the air at around 50 times the speed of sound.
The force of the meteor entering the atmosphere compressed the air ahead of it, creating a shock wave. This shock wave of compressed air pushed back on the meteor, compressing and heating it in return, until the stresses became too great for the meteor to stay together. When it exploded, this blasted meteor fragments in all directions, including straight ahead, along its original path. That would not have been the end of the shock wave, though. It would have continued along the meteor's path, losing size and strength due to friction with the air, until it was either reduced to nothing or it encountered something to stop it.
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Apparently, it persisted until it reached Lake Chebarkul, and that time, all that was probably left was just a narrow blast of hot, compressed air and some small meteor fragments.
Thus, the hole in the ice on the lake was likely created by what amounted to a shotgun blast from space.
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