Musk has already mapped out an approximate number of people he imagines living in the Mars colony (80,000), as well as how much a ticket to Mars might cost--$500,000.
But first, he said, SpaceX has to design what he calls a "rapid and reusable" rocket that can land vertically. "That is the pivotal step to achieving a colony on Mars," he told an audience at the Royal Aeronautical Society in London last week.
If SpaceX or another company can't come up with a rocket that can be reused and refueled (like we reuse airplanes), then he said colonizing Mars would be prohibitively expensive.
Musk described creating a rocket that could shuttle between Mars and the Earth as "possible, but quite difficult."
But that hasn't stopped him from mapping out a vision of how a colony on Mars might grow. The first step, of course, is getting a manned mission to Mars, which Musk said he thinks SpaceX can do in 10 to 15 years.
Next, he envisions sending 10 people to the Red Planet, along with supplies to build transparent domes, Space.com reports. If the domes are pressurized with the CO2 in Mars' atmosphere, the colonists could grow Earth crops in the soil on Mars.
As the colony became more self-sufficient, space on the rocket could be filled with people rather than supplies.
And those numbers Musk tossed out are not random. He arrived at 80,000 colonists by estimating that by the time a Mars colony is a reality there will be 8 billion people on Earth. Musk said he thinks 1 in 100,000 people will be ready and willing to take the journey to Mars. As for the $500,000 ticket--he said that while it's a lot of money, it is a sum of money that someone who has worked hard and saved carefully might be able to afford.
And as to whether the American taxpayer should contribute to a colony on Mars, Musk says yes. A colony on another planet is life insurance for life collectively, he said during his talk. He added that it would be a fun adventure to watch, even if you aren't planning on going yourself.
If you'd like to see the talk for yourself, check out the video below.