Elon Musk Outlines his Plan for Colonizing Mars and Why We Should Do It, SpaceRef [Includes the full video of Elon Musk's talk and the presentation slides.]
"In a presentation today at the 67th International Astronautical Congress in Guadalajara, Mexico, Elon Musk outlined his ambitious plan to colonize Mars. His personal motivation is to make humanity a multi-planetary species. The reason is to avoid an extinct level event on Earth that would wipe out humanity.
To achieve a self-sustaining society you'll need to send 1 million people to Mars which could take 40-100 years. To get those people there Musk introduced the SpaceX Interplanetary Transport System. The rocket, the largest ever built, could carry 100 plus people per flight and would need 10,000 flights to carry those million people. Musk hopes to be able to eventually carry 200 people per flight which would reduce the number of flights needed."