<Ul> <Li> <P> This GALEX image of the Cygnus Loop Nebula could not have been taken from the surface of the Earth because the Ozone Layer blocks the ultra-violet radiation emitted by the nebula . </P> </Li> </Ul> <Li> <P> This GALEX image of the Cygnus Loop Nebula could not have been taken from the surface of the Earth because the Ozone Layer blocks the ultra-violet radiation emitted by the nebula . </P> </Li> <P> This GALEX image of the Cygnus Loop Nebula could not have been taken from the surface of the Earth because the Ozone Layer blocks the ultra-violet radiation emitted by the nebula . </P>

In stratosphere the level of ozone is naturally regulated by