# Why do meteorites explode?

Some meteorites just blaze away, streaking through the sky. This is clearly explained, as they either slow down enough for the flame to cease, or ablate in their entirety, turning to vapor.

But some, like the Chelyabinsk meteorite, explode violently.

What effect is responsible for this?

Can it be that with their irregular surface acting as a turbine they enter a spin of increasing speed, and once the centrifugal force reaches a certain level, it causes the meteorite to break apart rapidly, hurling parts of it in all directions at speeds far exceeding its speed so far?

The Chelyabinsk meteor didn't explode.

In fact meteors in general usually don't explode, this is a common misconception.
When an object at orbital speeds ($\sim11 km/s$) enters the atmosphere, this speed corresponds to extremely high mach-numbers (M$\sim 30$). This generates a strong shock-front in front of the meteor which causes the meteor to heat up enourmously.
To give a feeling of how important this heat-up is, you can look up on Wikipedia that already at Mach-numbers of 2-3 there are severe engineering problems in not letting aircraft overheat. At Mach-numbers of 30, the air in the shock is so hot that it locally ionizes the air and easily evaporates the solids away from the falling meteor. Upon reaching the ground one hears this shock as loud thunder.
The other thing that happened with the Chelyabinsk meteor is that it broke up in mid-flight. This caused the total solid surface of the meteor that is exposed to the shock to momentarily increase strongly. More surface exposure to the heat causes more surface to glow. This lasts until the smaller fragments that resulted from the breakup evaporate themselves.

Taken together, the mach-shock and the increase in glowing surface area upon break-up give the impression of an "explosion".
Also for an explosion a reservoir of energy would need to be suddenly tapped, which is just not there.

• I'm a little murky on the distinction you make between "breaking up" and "exploding" --- you seem to be using these terms in a technical way that I'm not accustomed to. – rob Apr 29 '16 at 22:26
• @rob: sometimes the break-up is quite non-violent. But in case of Chelyabinsk there was heavy damage to ground infrastructure, many wounded people - is that all result just of the (continuous, lengthy) shock front reaching the ground? – SF. Apr 30 '16 at 6:23
• @SF: The meteor still hits pretty fast. That should account for all the damage. – AtmosphericPrisonEscape Apr 30 '16 at 10:26
• @rob: Imagine you travel on the comet. Then you are in its rest-frame. From this perspective an explosion would generate motion in all directions equally. This needs an energy source. However a break-up is just the comet loosing its structural support and then relatively gently falling to pieces. – AtmosphericPrisonEscape Apr 30 '16 at 10:28
• I'm completely sure that if a pretty solid (iron) meteorite is shaped in such a way that the air makes it enter a violent spin, the berak-up will be anything but gentle. But I have no clue how often this could occur. – SF. Apr 30 '16 at 11:40

Meteorites don't explode. To understand them properly we need to know it's stages.

• Meteoroid (small piece of rock travelling in outer space towards a planet or satellite)
• Meteor (This is when meteoroid reaches the planets atmosphere and is travelling)
• Meteorite (This is after the meteor has fallen on the surface)

As I mentioned above meteorites don't explode. But, when a meteor is big enough and is still travelling in atmosphere, it produces bright flame around it.

There is a common misconception that the flame is produces is due to friction of meteor with atmosphere. But, the actually when the meteor travels in atmosphere, it compresses the air below it. When gas is compressed heavily it produces incandescence and glows. This is what exactly happening here also.