This image presents us with wide troughs with a narrow ridge running down the middle. How did these form? Chryse Planitia is flat lowland region in the Northern Hemisphere of Mars that was chosen for the landing sites of the Viking 1 and Mars Pathfinder craft. The surface rocks of Chryse Planitia are believed to be eroded remnants of basaltic lavas carried to the site by large floods during Mars’ early history.