Elon Musk can make another 100 billions by claiming a chunk of Mars territory and selling NFTs backed by 1 acre lots of Mars land. The NFTs will be real so long as Elon gets the US gov to recognize his landlord rights on Mars, at least near the location of his first rocket landing. The thing is, he can start selling NFTs right now, as his promise alone is this valuable.
Just as was done a generation above with selling off lots in the desert west ... Barring any international treaties that would probably prevent any such claims, the general rule is that you or a physical representative have to set foot and survey before you can make a claim. And stepping onto Mars in one spot would not be sufficient to claim the whole planet.
Ah, you're being nitpicky. Buyers of those NFTs will be betting on Musk setting the foot first, and thus claiming a big enough chunk of Mars land. Potential returns are very large when there's a lot of ambiguity and risk. By the time Mars is regulated by a pile laws, returns will be low and a million dollars will buy a tiny lot. Buyers of NFTs will also speculate on finding expensive minerals under the Mars surface. If you have billions rotting in stock market, investing 1% into this, backed by the Musk's reputation and potential, is a no brainer.