Mars' river valleys are an iconic feature, formed billions of years ago in a different climate. Planetary Scientist Tim Goudge joins Jake to talk about how they were formed, and how one such formation method may have been more important than we once thought.We talk Mars river valley networkTim's PaperCoverage of Tim's PaperFollow TimUT Planetary Surface Processes GroupTim's TwitterFollow Jake & WeMartiansWeMartians.comPatreon (https://www.wemartians.com/support)WeMartians Shop (shop.wemartians.com)Mailing List (https://wemartians.com/signup)Twitter (@we_martians)Jake’s Twitter (@JakeOnOrbit)Off-Nominal PodcastMarsti.meMarsti.meLearn about time on Mars! See live mission clocks, learn about sols and Mars years and solar longitude, and discover your Martian birthday! Visit Marsti.me, a new site from Jake.Tharsis Planetary ParkCelebrate Mariner 9's 50th anniversary with the Tharsis Planetary Park design at the WeMartians shop today! You can get it in a t-shirt or on a coffee mug.