Quote:
Originally Posted by Robh
It states such asteroids (here 10 metres across) hit Earth once per decade. Anyone know why would it have exploded at that height (15 to 20 kms)? Was that because its trajectory was more tangential than normal to the Earth's atmosphere on entry?
Rob
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The height at which an asteroid or large object detonates in our atmosphere depends on several factors...
1. Air resistance
2. What the asteroid is made out of and
3. Structural integrity of the asteroid
4. Velocity of impacting object
An iron asteroid of the same size would've hit the ground, or come very close before it flash vapourised. A stony-iron or solid stony asteroid of 10m in size would do so at around the altitude given. The stresses caused by heating and drag as the asteroid entered the atmosphere would increase until it exceeded the structural integrity of the materials it was made out of. If it was full of cracks and cavities to begin with, or just a loosely held together rubble pile, it would fly apart at a much greater altitude...probably 30-50kms, or higher.
Anything larger than 30m in size that was iron or solid stone would hit the ground nearly intact, leaving a big crater (Meteor Crater in Arizona was formed from a 50m stony-iron asteroid that impacted at 25kms. The blast was the equivalent of a 20MT nuke). But an asteroid that was full of cavities and cracks, you'd be looking at an impactor having to be 100m or larger to survive.