The primary objective of the ExoMars mission is to identify potential signatures of ancient life, so criteria for landing site selection included the presence of rocks suitable for the concentration and preservation of organic matter and, of course, engineering and safety constraints.

Oxia Planum is the site selected by ESA for the landing of the ExoMars mission: it is a flat region located on the eastern edge of Chryse Planitia, at low elevation (between about 2600 and 3100 m) and with several lines of evidence suggesting a long aqueous history during the Noachian era. In particular, it shows an extensive fractured unit, potentially of sedimentary origin. An ancient delta belonging to the Coogoon Valles river system lies above the clay unit in the eastern part of the landing zone. Another geologic unit of interest covers the clay unit at various locations in the landing zone. This unaltered unit may be formed by lava flows or late fluvial processes. Finally, an extensive mantle deposit, plausibly of erosional origin, covers the clay unit and deltaic deposits. The probability of landing on this clay unit is high, and the probability of landing close enough to drive to a clay exposure is even higher.