I don't seem to understand the logic here. As I understand the idea of "Late Great Filter is bad news", it is simply about bayesian update of probabilities for hyphoteses A = "Humanity will eventually come to Explosion" versus not-A. Say, we have original probabilities for this p = P(A) and q = 1-p. Now, suppose, we take Great Filter hyphoteses for granted, and we find on Mars remnants of great civilization, equal to ours or even more improved. This means that we must update our probabilities of A/not-A so that P(A) decreases.

And I consider this really bad news. Either that, or Great Filter idea has some huuuuge flaw I overlooked.

So, where am I wrong?