Since at least the early 2000s, Elon Musk has been obsessed with the idea of colonizing Mars, a hostile and arid planet tens of millions of miles away. He’s clearly been personally obsessed with the idea, showing up at public events while wearing an “Occupy Mars” T-shirt. Musk, who has a long track record of imbibing in drugs like ketamine, appears to be going through it these days. Along with a slew of anti-immigrant posts, Musk has also been retweeting optimistic visualizations of what a Moon city might look like. More on Musk: Elon Musk Announces Huge Change: Self-Growing City on Moon Now Top Priority at SpaceX