Anyone who keeps track of Elon Musk knows the world’s richest man has a penchant for setting aspirational schedules for his companies. SpaceX misses those ambitious timelines so often that Musk has joked the company specializes in making the impossible late.

So, if you have an opportunity to interview him, why spend time asking Musk to prognosticate when one of his companies will do something years in the future? This is especially true for things that are impossible to know, like when will SpaceX land a Starship on Mars? Predictably, Musk replied to that question Thursday by saying it was feasible for Starship to achieve a Mars landing—without people on board—in three or four years.

Landing Starship on Mars in 2026 or 2027 is probably among the least likely of all the feasible outcomes, but setting this timetable helps keep SpaceX’s workforce razor-focused. Starship is a revolutionary design, with the goal of becoming a rapidly reusable rocket that could fly thousands of times per year. It’s also the largest rocket ever built, with at least twice the thrust of NASA’s Saturn V rocket from the Apollo program more than 50 years ago. Musk described Starship on Thursday as a “generalized transport system to anywhere in the Solar System.”