Just to complete the circle: The opposite would be Earth was hit by other objects in the distant past, and the collision blew large chunks of Earth into space.

Just to complete the circle: The opposite would be Earth was hit by other objects in the distant past, and the collision blew large chunks of Earth into space. Complete with B3 and RNA. (Especially credible as the body in question is a near Earth asteroid.) All the posited explanations are reasonable hypotheses in my opinion.