High profile trips by billionaires Richard Branson and Jeff Bezos have more people thinking about the future of space tourism. There’s a long way to go before that’s common, but one destination for would-be space explorers is Mars. NASA scientists are working on robots to help explore more of the planet first. Marketplace’s Kimberly Adams talks with Ali Agha, a principal investigator and research technologist at NASA’s Jet Propulsion Laboratory, who’s testing a fleet of robots, including ones from Boston Dynamics called Spot by sending them into caves in Northern California.