Enlarge / Elon Musk speaks during the 67th International Astronautical Congress in Guadalajara, Mexico, on Tuesday, Sept. 27. (credit: Susana Gonzalez/Bloomberg via Getty Images)

When he delivered his Mars colonization presentation at the International Astronautical Conference in September, SpaceX founder Elon Musk spent a lot of time discussing the Interplanetary Transport System rocket and spacecraft, But he offered precious little information about what the firsts visitors’ life on Mars would look like.

During an AMA on reddit Sunday afternoon, he filled in a few of those details. After a user named El-Psy-Kangaroo asked about initial missions to Mars, Musk replied that the first “Red Dragon” spacecraft sent to Mars, possibly in 2018 but more likely 2020, would prove the company could land propulsively on the red planet, and then experiment with chemical reactions to find the best way to derive methane and water from the Martian atmosphere. The resulting propellant would, eventually, be used for return missions from Mars.

The first large ITS spacecraft sent to Mars, nicknamed “Heart of Gold” after the ship in The Hitchhiker’s Guide to the Galaxy, would likely be filled mostly equipment to build a propellant plant on Mars. The first crewed mission would then carry perhaps a dozen colonists and the equipment needed to build a “rudimentary” base and finish the propellant plant. The company would then try to double the number of flights every 26 months, during each Earth-Mars orbital rendezvous. “We are still far from figuring this out in detail,” Musk acknowledged.