SpaceX was founded with the goal of going to Mars one day. That’s why CEO Elon Musk made his way down to the 67th International Astronautical Congress in Guadalajara, Mexico last September: to provide details on the vision for exactly how he and his team were going to accomplish such a monumental feat. It’s called the Interplanetary Transport System, and SpaceX wants to make it the premier transportation method for getting around the solar system.

But this is all part of a larger goal of trying to, as Musk put it, turn humanity into “a space faring civilization and a multiplanetary species.” The ITS is a multistep process on its own, but it’s just one piece in helping to establish the first-ever colony on Mars.

This month, the journal New Space published a new paper written by Musk which goes into more detail about the ITS. And Musk takes the opportunity to double down on what this whole endeavor is all about: creating a self-sustaining city on Mars.

“There has been a lot of great work by NASA and other organizations in the early exploration of Mars and understanding what Mars is like,” Musk writes. “Where could we land? What is the composition of the atmosphere? Where is there water or ice?

“We need to go from these early exploration missions to actually building a city,” Musk writes.

Musk argues that the major obstacle right now isn’t that it is impossible to go to Mars — it is that it is unaffordable. The ITS depends on the invention and testing of many different new technologies which aren’t supposed to make a journey to Mars possible, but simply less expensive and more sustainable.

”Using traditional methods, taking an Apollo-style approach, an optimistic cost would be about $10 billion per person,” he writes. It took an estimate $100 to $200 billion in today’s dollars to send just 12 people to the surface of the moon.

A city, obviously, is made up of a lot more people than that. Different definitions use different metrics, but Musk and SpaceX have a simple target: a population of one million. It goes without saying sending one million people to the red planet cannot cost $10 billion person.

So Musk and his team developed another simple target: if you’re not going to buy a house here on Earth, why not spend that money on a trip to Mars? At that rate, the cost of a single person going to Mars would be around $200,000. “Then I think the probability of establishing a self-sustaining civilization is very high,” writes Musk. “I think it would almost certainly occur.

“It gets to the point where almost anyone, if they saved up and this was their goal, could buy a ticket and move to Mars — and given that Mars would have a labor shortage for a long time, jobs would not be in short supply.”

To that end, SpaceX is working on a ton of spaceflight architecture which aim to make all of the parts fully reusable many times over, facilitate refueling in space to reduce the power needed for launch, create a realistic method of fuel production on Mars itself, and much more. None of those things are required if the goal is simply to visit Mars for the sake of achievement. But Musk is thinking bigger — he wants to see humanity stretch its reach to places far beyond the third rock from the sun.

Photos via SpaceX