Where are their perfect circular holes?
Because of the speeds they are going,
When they contact the earth, they explode.
Stick a fire cracker in some sand and light the fuse.
When it goes off it will leave a circular hole, or crater.
How can meteors explode on the Moon, where their is no oxygen?
The crater should be based on the angle of impact, which will not be at 90 angle
While traveling through the space, meteoroids have pretty low temperature.
When they hit the surface, their kinetic energy converts into heat.
(When you hit piece of metal with hammer, it gets hotter, due to kinetic energy of hammer cinverted into heat. Low speed of hammer requires more than one hit.)
Objects expand at higher temperatures.
Sudden increase in temperature gives parts initial speed due to thermal expansion.
Increase in temperature is very high because speed is very high. Tens of thousands mph or more.
Combination of hit and heat breaks meteoroid into pieces and they fly all around.
They don't need oxygen / burn to explode.
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Another example of explosion without burning is how Prince Rupret's Drop explodes on collision with a bullet.
(They are much more elongated compared to meteoroids.)
First the bullet explodes, and then the Drop itself.