New USGS Maps of Mars Reveal Ancient Oases

Flyover of the southeast Ceti Mensa map. Distinct groups of rock layers, called geologic units, are shaded in different colors, with dark browns representing the oldest rocks and green representing the youngest rocks. All of these rocks formed as wind-blown sand that became trapped in shallow, ephemeral lakes, similar to the wet playas of the desert southwest US. The irregularly-shaped green unit is a large landslide that brought rocks from higher up on Ceti Mensa down into this area. A new set of high-resolution geologic maps reveal complex geologic processes that suggest a dynamic, wet environment once existed on early Mars, according to the USGS.