"I totally understand that you would," she tells him. "It's OK, I accept that. Totally."

"It's not that I like Mars better than I like you," he assures her. They peck each other on the lips.

But there is something powerful that draws Maxwell to Mars. It's partly the idea of being on the surface of another world. There's also his own mortality. He believes the radiation treatments he had in his 20s will ultimately lead to a different form of cancer (he actually had a possible thyroid cancer a few years ago, which turned out to be benign). Maxwell estimates -- without a hint of regret in his voice -- that he has about 20 years left to live.

"I've only got so long anyway, you might as well make it something really good. Right? You might as well make it count," he tells me and Lichtenberg. "And what am I going to do that's going to be better than actually going to Mars? Go on, name three things I'm going to do that are better than that."

"Drive a Mars rover," says Lichtenberg.

Maxwell agrees his job is "awesome" but says going to Mars would be "even better."

With that level of passion and spirit, Maxwell may one day indeed follow his Curiosity.