Today, the head of one of the world's largest e-commerce giants is stepping down. Jack Ma, chief executive of Alibaba says he's too old to run an internet company at the decrepit age of 48. Plus, all this week we're talking about the near future of tech, and today we look at what's coming in the next decade of space exploration. Marketplace Tech talks to Adam Steltzner, a NASA engineer who navigated the incredibly challenging landing of the Mars Curiosity Rover. Steltzner says it's about putting people on Mars. Also, he discusses looking for life on Jupiter's moon Europa.