On entering which layer of the atmosphere from space do the meteorites burn up?

When an object enters the atmosphere from space at very high speed, it heats up mainly because it rapidly compresses the air directly ahead of it, along with colliding with air molecules; this compression and collision energy converts into intense heat. How intense that heating gets -- and whether it is enough to fully vaporise (ablate) the object -- depends on how dense the surrounding air is at that altitude, not on altitude by itself.

A meteoroid entering from space first passes through the exosphere and then the thermosphere, where air density is still low enough that any heating stays gradual. It is only on reaching the mesosphere, roughly 50-85 km above the surface, that the air becomes dense enough for compression and molecular collisions to generate the sudden, intense heat that ablates most meteoroids almost completely -- which is why this region is popularly nicknamed the "shooting-star layer."

• Thermosphere: the layer where the ISS and most satellites orbit; individual air molecules here can carry very high energy (which is where the layer gets its name), producing gradual warming on a passing object rather than the sudden intense heat that fully consumes it.

• Exosphere: the outermost fringe of the atmosphere, gradually thinning into space; its widely scattered atoms give a passing object only occasional, faint collisions, a far gentler encounter than the intense heating that ablates a meteoroid.

• Stratosphere: home to the ozone layer and the cruising altitude for most jet aircraft; its temperature rises with height purely because ozone absorbs solar UV radiation, a steady effect quite unlike the sudden intense heating produced when an object enters at high speed.

So, meteoroids ablate almost completely in the mesosphere, well before they would reach the denser stratosphere.