Yup. And in order for there to be flowing water on Mars, conditions had to be much much warmer on the red planet in the past. Warm enough to support Earth-like life.
If life came to Earth aboard a comet (as opposed to developing here), it most likely arrived on Mars as well. In that case, the early solar system was probably teeming with life (seeds), and in that case, it could be very common elsewhere.
