The two billionaires are locked in a race to send humans to space, with Musk’s SpaceX far in front of Bezos’ Blue Origin venture. But the two differ on what to do when humanity arrives in space: Musk wants to establish a self-sustaining city on Mars, while Bezos would rather see humans orbiting Earth in giant space stations.

Musk’s vision receives a lot of publicity, but space consultant Rand Simberg tells Inverse that Bezos’ goal is the “more expansive.”

“Elon is what [science fiction writer Isaac] Asimov would have called a planetary chauvinist,” he says. “He thinks people need to be on planets. He wants to be a multi-planet species. That’s nice, I guess. But Bezos actually has a more expansive vision.”