Against the current with lava flows

Primeval lava flows formed the massive canyons and gorge systems on Mars. Water, by contrast, was far too scarce on the Red Planet to have cut these gigantic valleys into the landscape. This is the conclusion of several years of study [“A network of lava tubes as the origin of Labyrinthus Noctis and Valles Marineris on Mars“] by ETH geoscientist Giovanni Leone… [More at links]