In a conversation that ranged from the physics of lithium battery technology to the burdens of parenting five kids, Elon Musk sprinkled several gems in his talk with Chris Anderson—the erstwhile editor of Wired—on the main stage at SXSW yesterday.

According to the 41-year-old Iron Man look-alike, PayPal founder, Tesla CEO, and SpaceX CEO/CTO, the biggest disappointment of his life will be if humans don't reach Mars in his lifetime. “It’s the first time in four and a half billion years that we are at a level of technology where we have the ability to reach Mars,” he told the rapt audience. “The sun is gradually expanding. In 500,000 million years—a billion at the outside—the oceans will boil and there will be no meaningful life on Earth. Maybe some very high temperature bacteria, but nothing that can build rockets.” Basically, humans should take advantage of the fact that we've figured out how to get out of here and do just that.

Becoming an “interplanetary species” will eventually be our most attractive (only?) hope for survival, Musk says, declaring that “space travel is the best thing we can do to extend the life of humanity.” So dedicated is he to SpaceX’s mission and to Mars exploration that he put the two in that order with reference to his own mortality: “I will go if I can be assured that SpaceX would go on without me . . . I've said I want to die on Mars, just not on impact.”

And Musk really does think that big. When asked by an audience member to recall the best piece of advice he ever received, he responded, “physics.”

The conversation turned to Musk’s personal life when Anderson asked about his parenting strategy. “Kids are great. You guys should all have kids! I don't see mine enough actually. What I find is I'm able to be with them and still be on e-mail. I can be with them and still be working at the same time.” When an incredulous Anderson, also the father of five children, pressed him, the billionaire double-CEO conceded that family time often included a nanny. “To make sure they don't kill each other.”

Despite overwhelming evidence that he is in fact super-human, Musk also admitted that having three job titles and five kids can be tiring. Of his pace he said, “I’d like to take it down a scootch,” and that last year “wasn’t much fun. In fact, it sucked. So my new year’s resolution was to have more fun. That’s kind of why I’m at SXSW.”

The final question came from an audience member who asked about “the biggest mistake” of Musk’s life. There followed a long, rather uncomfortable pause in which he appeared not be able to think of any mistakes at all. But Musk’s eventual answer was a surprising one for the scientifically-minded entrepreneur: “The biggest mistake, in general, I’ve made, is to put too much of a weighting on someone’s talent and not enough on their personality. And I've made that mistake several times. I think it actually matters whether somebody has a good heart, it really does. I’ve made the mistake of thinking that it's sometimes just about the brain.”