Resolves YES if Elon Musk steps onto the surface of Mars and NO if he dies without ever doing so.
What if, in his will, he trolls us by having someone remove the foot from his corpse, and carry it to Mars?
As people, we know that is the intent, but technically speaking, he's still "setting foot." I think the man who likes physical puns like "let that sink in" would like the other one as well.
The man is currently 52. It'll be at least a decade (probably 2) before any human sets foot on Mars let alone "regular" people. It'll be an extraordinarily uncomfortable journey, for which you'll need to be in absolute peak physical condition. Elon is a billionaire. He doesn't want to spend his golden years confined to a couple dozen cubic square feet eating protein packets on an exercise bike and peeing into a hose. He hasn't even been to low Earth orbit yet! Trust me, he doesn't want to go.