Famed astrophysicist Neil deGrasse Tyson held an “Ask Me Anything” session on Reddit on Sunday, telling readers that he’s ready for all questions as long as they’re limited “to life, the universe, and everything.”

As the focus turned to space exploration, somone asked Tyson if he’d consider a trip to Mars. Tyson replied that since he really likes Earth, it’d have to be a round-trip ticket. Then he tacked on another condition for the boss of SpaceX and Tesla TSLA, -1.77% .