[Windflier]

We really need to go no further than planet earth to estimate what the chance would be of life existing on other planets.

If you want to use Earth to figure out the possibilities of life arising on other planets, then you've got to assume that the universe is crawling with life.

Lifeforms have managed to inhabit nearly every niche imaginable on this planet. Using that observation as your starting point for hypothesis, you have to conclude that the same thing has happened throughout the cosmos.

[mtg]

If you want to use Earth to figure out the possibilities of life arising on other planets, then you've got to assume that the universe is crawling with life.

You're exactly 100% wrong with that assumption. If you accept the scientific evidence of a natural beginning of life (and the evolution of life) on earth, that evidence clearly indicates the probability of life on any other planet is ridiculously small.