Chloride-bearing deposits on Mars

Across the southern highlands of Mars, approximately 640 sites of chloride-bearing deposits have been identified using the Thermal Emission Imaging System (THEMIS). These isolated, irregularly shaped patches (approximate size range of 0.33 – 1300 km2, with an average size of 24 km2) have been dated to the older geologic periods on Mars: Noachian (4.5 – 3.5 billion years ago) and Hesperian (3.5 – 2.9 billion years ago) periods.

Source: Wikipedia — Chloride-bearing deposits on Mars (CC BY-SA 4.0)