The search for life on Mars is a cornerstone of international solar system exploration. In 2018, the European Space agency will launch the ExoMars Rover to further this exploration. The key science objectives of the ExoMars Rover are to: (1) search for signs of past and present life on Mars, (2) investigate the water/geochemical environment as a function of depth in the shallow subsurface, and (3) to characterise the surface environment.

The choice of landing site is vital if the objectives are to be met. The landing site must: (i) be ancient (≥3.6 Ga), (ii) show abundant morphological and mineral evidence for long-term, or frequently reoccurring, aqueous activity, (iii) include numerous sedimentary outcrops that (iv) are distributed over the landing region (the typical Rover traverse range is a few km, but ellipse size is ~100 by 15 km). Various ‘engineering constraints’ also apply, including: (i) latitude limited to 5º S to 25º N, (ii) maximum altitude of the landing site 2 km below Mars’s datum, (iii) few steep slopes within the uncertainty ellipse.

In March 2014, the first ExoMars Landing Site Selection Workshop was held, during which eight different landing sites were presented and discussed. In October 2014, ESA downselected to four final sites: Mawrth Vallis, Oxia Planum, Aram Dorsum and Hypanis Vallis. A second workshop in December 2014 allowed further discussion of these four sites. Here we present an update on the selection process, and discuss the relative merits of each site.