Sculpted by ancient water flowing on the surface and one of the most remarkable outflow channels on Mars, Mawrth Vallis was once a potentially habitable place. Seen here by ESA’s Mars Express, with a length of 600 km and a depth of up to 2 km, it is one of the biggest valleys on Mars. See http://www.esa.int/spaceinimages/Images/2016/09/Mawrth_Vallis_martian_mosaic
