The Perseverance rover has just landed on Mars. Meanwhile, its precursor Curiosity continues to explore the base of Mount Sharp (officially Aeolis Mons), a mountain several kilometers high at the center of the Gale crater. Using the telescope on the ChemCam instrument to make detailed observations of the steep terrain of Mount Sharp at a distance, a French-US team headed by William Rapin, CNRS researcher at the Institut de Recherche en Astrophysique et Planétologie (CNRS/Université Toulouse III/CNES), has discovered that the Martian climate recorded there alternated between dry and wetter periods, before drying up completely about 3 billion years ago.