Armchair astonomer here. If the bodies involved in the collision are already in stable orbits around earth, most of the debris from the collision will remain re

Armchair astonomer here. If the bodies involved in the collision are already in stable orbits around earth, most of the debris from the collision will remain relatively true to its orbit prior to impact, though the force of the collision will spread the debris apart over time. Any orbits remotely close to earth will decay eventually, but that would depend on quite a few factors: it is possible small debris would remain orbiting for quite some time. The small stuff is what worries me the most - objects less than a square centimeter. A head on collision would be incredibly violent and would disperse a large cloud of debris over a large area - some of that would fall back to earth quickly. This would be incredibly unlikely, given that most objects above Earth orbit in a relatively similar set of planes and inclinations. A more likely scenario would be two similarly inclined orbits overlapping, with the satellites or debris impacting shallowly and at relatively (to orbital velocities, that is) low energy. It wouldn't take much to shred apart much of the more delicate instrumentation orbiting above our heads, which would similarly endanger more sensitive equipment, and so on.