This week we talk with Kenneth Williford, the deputy project scientist for the Mars 2020 Rover. He's an expert on where biology, geology, and chemistry collide to inform the search for evidence of ancient microbial life in rocks. We also chat with graphic design artist Rachel Ignotofsky about her new book, Women in Science. This illustrated guide profiles 50 women in STEM fields, from ancient times until the present, who have shaped our world.