With Elon Musk increasingly thinking about making humanity a "multiplanetary" species, talk has turned to where people would live.
Naturally, the enigmatic Musk has a plan for that.
The 49-year-old SpaceX CEO said that in order to build a city on Mars, humans would have to live in "glass domes at first."
Eventually, the Red Planet could be "terraformed to support life, like Earth," Musk tweeted.
That process will be "too slow to be relevant in our lifetime," he added, though it's important that a base is established on Mars sometime soon.
"At least a future spacefaring civilization – discovering our ruins – will be impressed humans got that far," he said.
In 2015, Musk discussed putting a city on Mars after a successful rocket landing by SpaceX. NASA’s long-term goal is to send a manned mission to Mars in the 2030s.
Musk published a paper in June 2017 on making humanity a multiplanetary species, laying out plans for having as many as 1 million people on Mars.
After his SpaceX company received its official certification from NASA to carry astronauts to the International Space Station earlier this month, which Musk described as a "great honor," the 49-year-old said the news would help inspire "confidence in our endeavor to return to the moon, travel to Mars, and ultimately help humanity become multiplanetary.”
Last month, Musk, who once advocated dropping nuclear weapons on Mars to make it more habitable, set a four-year timeline for an unmanned SpaceX mission to Mars but cautioned the timeline was "only a guess."
In 2018, the SpaceX and Tesla CEO said there was a "70% chance" he would move to Mars but with the caveat that there was a "good chance" of dying on the way to the Red Planet. Two years prior, he laid out an ambitious plan to put human life on Mars.