For a 40000 ton asteroid, the meteoroid would have, as a moon, an orbital speed of two micrometers per second.
:AMR:
Really?
Why?
I haven't done the calculations myself, but the 2 um/s sounds plausible. The reason is that the little asteroid has hardly any gravity at all. A "moon" orbiting it just a mile away from its surface would have to be moving pretty darn slowly, else it would fly off into space. If a moon was orbiting it farther out, the gravity it felt would be extremely small, so the moon would have to have an extremely small speed to stay captured. Since the main asteroid was what, 17,000 miles away (?), it's just implausible that there could be a moon at all at that distance.
There were no impacts. One went past Earth and the other burst in the atmosphere.
There was one impact - the smaller rock impacted with the Earth, because the atmosphere is part of the Earth.
Look, Stripe (and all the other folks trying to defend Enyart here), there's just no way to make this idea work. If the rock and the asteroid were travelling together, they necessarily would have had to be coming from the same general direction, even considering that the Earth's gravity would have bent the smaller rock's path somewhat near the end.
If the rock had at one time been associated with the asteroid but its orbit got perturbed, then its timing would also have been different, and they would not have arrived anywhere near the same time.
It just doesn't work. Give it up.