A pre-mortem is an exercise in which you assume a plan has already failed, then work backwards to name the causes — while there is still time to fix them.
The technique, popularized by the psychologist Gary Klein, flips the post-mortem forward in time. Rather than asking "what could go wrong," which invites optimism, it asserts "it went wrong" and asks why — which gives people permission to voice the doubts they would otherwise soften.
A pre-mortem works because certainty is the enemy of foresight. Assuming failure has already happened removes the social cost of predicting it.
A BadMars Mission Report is a pre-mortem run by an adversary. It does not ask whether your plan might fail — it assumes the hostile reading and files exactly where and why, with the single biggest cause named as the Frog.