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.".

In 2015, Musk discussed putting a city on Mars after a successful rocket landing by SpaceX.

RESEARCHERS DISCOVER MARS HAD WATER BEFORE THERE WAS LIFE ON EARTH.

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."