Water on Mars. Image 2 of 2. Computer artwork of the coast of the sea (left) thought to fill the Isidis Planitia (Isidis Plain) on Mars 3.5 billion years ago. This view looks east. Ice (white) lies on the highlands to the south, several kilometres above the lowland plain. The water was ultimately lost due to the thin Martian atmosphere and weak gravity. Mars is now a desert world. The crater mountains of the Libya Montes are seen down right. This image is hundreds of kilometres wide. The topography was drawn with Terragen software, using data from the laser altimeter on the Mars Global Surveyor probe. For this area today, see image R350/171.