Is Abortion killing a Life or Tissue?

I was thinking about this the other day, mainly due to the recent Awake! on Abortion.

Some doctors claim that women aren't aborting a life, just tissue. And this gives the doctors credibility or at least an excuse to help the patient go through with the costly procedure.

Well consider this:

If scientists or astronauts went to Mars and found even the smallest cells dividing on the surface of the planet, the next days' headlines would read "LIFE FOUND ON MARS". So why would we think that it isn't a life in a woman's womb that is being aborted, even when it's just a cell dividing and dividing again on itself? It's a life, even though it doesn't breathe yet... science will call it life.