CREDIT X X X X X X X X X X X X X X X GULLIES ON THE WALL This false-color image shows a crater wall in Utopia Planitia, with gully channels suggestive of water's activity. Some of the fractures resemble terrestrial ones that occur when ground ice is present. N AS A / J PL- CA LTEC H / U N I V E R S IT Y O F A R I ZO N A s k y a n d t e l e s c o p e . c o m * N O V E M B E R 2 0 17 21