Update, 1:21 p.m. PT: The live blog has concluded. Look for more coverage and reaction on CNET. We'll also be discussing the news live on the CraveCast today at 3 p.m. PT.
Note: We are updating this post live as Elon Musk unveils his opus -- a plan to extend human civilization beyond Earth, starting with Mars -- at 11:30 a.m. PT.
1:21 p.m.: Someone from Funny or Die just suggested Michael Cera should be the guinea pig that makes the first trip to Mars. Elon is not amused.
As the questions continue, we're going to wrap up our live blog here. In summary, Elon Musk and SpaceX want to start sending ships to Mars in a few years, followed by people, followed by a lot more people. He's completely serious about having a self-sustaining city on the Red Planet within a century. If you want to process this really big announcement with us, join us for a live discussion on the CraveCast at 3 p.m. PT.
1:16 p.m.: Musk compares establishing a travel link between Earth and Mars to building the first railroad to California. It seemed silly at the time, he says, because there were so few people on the West Coast, but it turned out to be an important link and obviously a few more people moved to California.
1:08 p.m.: Musk acknowledges that the first journeys to Mars will be risky and there will be a chance of dying.
1:06 p.m.: OK, time for questions. Someone asks a very pointed and vulgar question about Martian sewage. Musk cuts it off: "No essays, only questions." But yes, he says, he's working on toilets and sanitation for Mars, the system could be nuclear-powered, he says.
Interstellar filling stations
1:04 p.m.: Musk talks about constructing fuel depots for spaceships exploring deeper in the solar system. Suggests possible filling stations on Enceladus, Titan, Pluto, the Kuiper Belt. But he's not sure about using the system for interstellar travel. He ends with a hat tip to Europa, which was in the news Monday, and is now taking questions.
1 p.m.: If this all actually happens, today will be a historic date forever. Oh god, there's a "Beyond Mars" section. No one ever accused Elon Musk of settling, and he's proving that again today.
12:55 p.m: "We're kind of intentionally a bit fuzzy on this timeline," Musk says. But the bottom line is we're on the way to Mars within about 10 years or so "if things go super well." Now there's a fascinating aside about developing a rocket cargo delivery service that could deliver cargo anywhere on Earth in about 45 minutes. Geez, slow down, Elon!
"We want to establish steady cadence that there's always a flight leaving" (for Mars using the SpaceX Dragon lander at first). Musk is talking about these first landings starting within a few years. Dragon can land on any solid or liquid surface in the solar system.
12:46 p.m.: I have to imagine that if almost anyone other than Elon Musk stood on a stage at a major international conference and put this plan forward with a straight face, they would be laughed out of the room. It's just that ambitious.
"Timelines: I'm not the best at this," Musk says. Good one, Elon! He stole my joke!
12:44 p.m.: Musk says once all of the components of the plan are in place, the estimated cost of moving to Mars could drop below $200,000 and eventually below $100,000 when the Martian economy really gets going, I guess.
12:42 p.m: A simulated fly-through of the crew compartment looks straight out of a science fiction movie. I wonder if the design was inspired at all by "Europa Report"? Looks very similar, or like a more spacious, futuristic version of the International Space Station.
12:38 p.m.: OK, some context for this SpaceX Mars rocket. Musk says it will have 42 Raptor engines capable of 128 meganewtons of thrust. That's something like three to four times more power than we got out of a Saturn V in the Apollo days. The Saturn V has basically been the granddaddy of all rockets since.
As for the spaceship itself, it's also huge. Musk says it will be capable of carrying 100 passengers per trip, but he sees that being increased to 200 at some point.
12:35 p.m.: Musk confirms that the Raptor engine we saw test-firing earlier this week is the engine that will be used in the Mars rockets.
Three times bigger than Saturn V rockets
12:29 p.m.: Oh my, the mass of the SpaceX Mars rocket would be three times that of the Saturn V rockets that took men to the moon. It's a little hard to understate the magnitude of some of the scales we're talking about here.
Musk says the rocket will be almost entirely made of carbon fiber and 120 meters (394 feet) long.
12:27 p.m.: Musk envisions a fully self-sustaining civilization on Mars of 1 million people within 40-100 years of the first Mars rendezvous. That seems aggressive, to say the least. Keep in mind that according to biographies of Musk, SpaceX's first commercial rocket launches came several years later than Musk originally promised.
12:23 p.m.: The rockets will rapidly send propellant into orbit and return for more about 20 minutes later. Exactly how long it will take for a returned booster to be checked out, refueled and then loaded with a propellant tanker? No word yet.
We're now seeing a graphical size comparison of how big the interplanetary rocket will be. Spoiler: It's big. Really, really big. No measurements mentioned, but it looks like a skyscraper next to a human.
12:21 p.m.: The below video, posted earlier Tuesday by SpaceX, closely represents what will actually be built, Musk says. The video ends with an apparently terraformed Mars. Is that part of the plan, too?
Getting to Mars and back
12:18 p.m.: The ideal propellant for traveling to Mars and back? Musk's talking about using super-cooled methane. This is different than what most rockets use for orbital missions. The Falcon 9 uses oxygen and a type of kerosene.
12:14 p.m.: Musk is now talking about how to make the Mars trip cheaper. A few of the keys, he says, include building a propellant plant on Mars, refueling ships in orbit and recycling rockets, as SpaceX is already doing with its Falcon 9.
12:09 p.m.: Musk jumps right into the economics of getting people to Mars with a graphic showing that using "traditional methods" would cost about $10 billion per person to get them to the Red Planet. To build a colony, we'd need to drop this cost drastically, he says. By about 5 million percent, actually. That's some real economic optimism!
Musk's vision here is almost unbelievably audacious. He's jumping right in to what's needed to build a society with regular travel between planets. This isn't just about exploration or building a small colony. He's really talking about building self-sustaining cities on Mars.
12:05 p.m.: But why Mars? Musk says it's better than the "hot acid bath" of Venus, and Mercury is too hot, too. Everything else is too far out, except for the moon, he says. Mars is better suited than the moon because of its size, resources and atmosphere.
Noon: "I want to make Mars seem possible... like something that we can do in our lifetimes."
"History suggests there will be some doomsday event, and I would hope you would agree that becoming a multi-planetary species would be the right way to go."
11:59 a.m.: The head of the French space agency introduces Musk.
11:56 a.m.: Elon Musk entered the auditorium about 10 minutes ago, but we've still yet to start. A longer-than-expected wait will come as no surprise to those who have ordered a Tesla. (Musk is also CEO of Tesla Motors.)
11:35 a.m.: The doors are open!
Less than an hour before Musk was set to take the stage at the International Astronautical Congress in Guadalajara, Mexico, on Tuesday, SpaceX posted the below concept video of its "interplanetary transport system" to its YouTube feed.
The animated video shows a SpaceX rocket blasting off from Cape Canaveral. The spaceship then separates and continues on its journey while the booster heads back for a landing at the launch pad where it is then loaded with a propellant tanker and blasted off again to deliver the tanker for a refueling of the spaceship in orbit.
The ship is now ready to head for Mars with its solar array deployed and astronauts ready to set up shop for humanity at a new, more red address.
The video ends with a successful landing before zooming out to show Mars morphing from the barren, dead-looking planet we know to one with water and an atmosphere, an apparent nod to Elon Musk's dreams of one day nuking and terraforming the place.
First published 11:02 a.m. PT.
Update, 1:21 p.m. PT: We just wrapped up our live coverage.