Elon was deep in conversation with Peter Diamandis, founder of the X Prize Foundation, when they talked about Musk's dream for humans to set foot on the Red Planet by 2026.  NASA's projection was 2033.

Elon waxed a little poetic, saying, "Going to Mars reads like that advert for Shackleton going to the Antarctic. You know it is dangerous. It's uncomfortable, and it's a long journey."

And then, he lowered the boom ... "You might not come back alive, but it is a glorious adventure and it will be an amazing experience ... Yeah, honestly, a bunch of people will probably die in the beginning."

Thing is ... he may be truth-telling, despite people not wanting to hear it.

Elon's take is that the upside justifies the downside ... "For the first time in the four and a half billion year history of Earth it has been possible to extend life beyond Earth and make life multi-planetary."

He went on ... "Humanity is the agent of life and we have an obligation to ensure the creatures of Earth continue even if there is a calamity on Earth, whether it is man-made or a natural calamity - if you look at the fossil record there are many mass extinctions. It is about ensuring we pass that threshold where it is self-sustaining if some calamity prevents the ships from going there."

Musk, who was barefoot during the interview, ominously asked, "What comes first - a self-sustaining city on Mars or World War Three?"