Common yeast can survive Martian conditions

all of those theories depend on one assumption, that life and our existence are products of a purely random collision of events.

IMHO, "We don't know" is the only answer to the question of how many planets have life on them or the probability of some forms of live existing somewhere. 0 is as valid as 10^128 until more than one other life supporting planet or moon is found to establish some baseline for speculation. otherwise, we're talking sci-fi here, in which case I think stargate's version seems decent.

There is the old theory about how life is entropy accelerating, and therefore in a grand sense the emergence of life is thermodynamically favored. Though, that says nothing about the absolute chance of it occurring.[1] Our observable universe is far from infinite.

[1] Though maybe it does speak to life tending toward evolving more complex, energy consuming systems, and its propensity to spread out into the universe.