Elon Musk believes humans will make it to Mars before the end of this decade.

The SpaceX boss tweeted his prediction on Wednesday in response to a message asking when the first crewed landing might take place. Musk replied, “2029.”

Musk founded SpaceX 20 years ago with the goal of creating a reusable rocket system to cut the cost of launches and increase access to space.

Having already achieved a great deal with his workhorse Falcon 9 rocket, which currently carries astronauts to and from the International Space Station and launches satellites for a growing number of companies and organizations, Musk has always seen the big prize as getting humans to Mars, and even creating a self-sustaining colony there.

However, his predictions, it has to be said, do tend to slip, so this latest one might, too. In 2016, for example, he predicted humans would reach Mars in 2026, a date that few people now see as realistic. Even 2029 sounds ambitious, with much work still needing to be done to pave the way for such a bold mission.

Musk would likely use SpaceX’s next-generation Starship rocket — comprising the Super Heavy booster and Starship spacecraft — for its Mars missions, though the vehicle is yet to take its first orbital test flight.

Subject to regulatory approval, Starship could take its first test flight in the next month or two, with a successful mission putting it on course for a lunar landing in the coming years, before any voyage to the more distant red planet is attempted.

Speaking about Starship’s development progress at a special event last month, Musk admitted that “there’ll probably be a few bumps in the road” for SpaceX’s most powerful rocket to date, but said he was sure his team of crack engineers could create something that’s “extremely reliable for human spaceflight.”

During the event, Musk also unveiled an animation showing what a future voyage to Mars could look like. Check it out below.

Besides having a spacecraft that can make it safely there and back, SpaceX will also have to ensure the astronauts have reliable equipment and ample supplies for what would likely be a multi-year voyage, one way longer than any crewed mission that’s gone before. And what about hazards such as radiation and Martian dust storms? This Digital Trends article explores the challenges of a crewed Mars mission in more detail.