It is not possible for an asteroid to do that. If a space rock hit our atmosphere, it would either burn up or rapidly lose speed and crash to the ground.
I know the white blood cell animation you are talking about.
White blood cells are not self-aware. It might be helpful to picture cells (and even large animals) not as the discrete objects that are seen by the naked eye, but rather as a cloud of "stuff". In the middle is the meat; on the outside is various liquids, particles, and gases that leak out. So, the white blood cell isn't keeping an eye on the bacteria and chasing it. It's increasing contact with the "stuff" that it recognizes as foreign.
When a sufficiently large asteroid[0] slams into Earth, the impact plume[1] can hoist matter off the surface. The velocity of said matter may be sufficiently high to escape Earth's orbit, potentially seeding the solar system with life[2].
I know the white blood cell animation you are talking about.
White blood cells are not self-aware. It might be helpful to picture cells (and even large animals) not as the discrete objects that are seen by the naked eye, but rather as a cloud of "stuff". In the middle is the meat; on the outside is various liquids, particles, and gases that leak out. So, the white blood cell isn't keeping an eye on the bacteria and chasing it. It's increasing contact with the "stuff" that it recognizes as foreign.