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From Wondry, I'm Stephen Johnson, and this is American Innovations.

While we've landed robots like Curiosity and Opportunity on Mars,

setting foot on the red planet is still the stuff of science fiction.

But we're getting closer.

In part, that's because of private space entrepreneurs like Elon Musk.

But it's also because of our guest today, Engineer and author, Dr. Robert Zubrin.

You might remember him from the first episode of our Mars series.

His work in the early 1990s, called Mars Direct, created the blueprint for Mars' exploration

that NASA and Musk are still relying on today.

But Zubrin doesn't just want to set foot on Mars.

He wants humans to call it home.

It will be hard, but that's the point.

The way Zubrin sees it, human culture needs new challenges to keep moving forward.

And what could challenge us more than living on another planet?

Dr. Robert Zubrin, thank you so much for joining us on American Innovations.

Thanks for inviting me.

So it's always such a pleasure for us and for our listeners to get to talk to someone

who's been featured in the stories we tell.

I think everybody's really dying to hear from you directly.

One of the things that comes across in your story is just this passion for Mars

...