European Space Agency and Roscosmos decided about designating two landing zones of future lander and rover send under ExoMars in 2020.
Two days ago on Tuesday, 28 march ESA announced about another step to ExoMars 2020. Agency decided to designate two landing zones, where possibly will land lander with martian rover onboard.
Both places were chosen mainly because of their low altitude. It is important because of planned technology used for landing and developed by Russian Lavochkin company for lander. It is basing on drag parachutes rather than on retro thrusters - lander will reduce its speed after passing certain distance and it will not be able to slow down earlier. Landing zone must be placed low enough to provide this distance. Another criteria were plain surface, lack of any large stones or any objects which could interrupt landing or deploying rover.
First place was designated already in 2015: 120 x 19 km ellipse is located at Oxia Planum (18.275°N 335.368°E). Another considered as potentially suitable for landing were selected following regions: Aram Dorsum and Mawrth Vallis. Recently after lasting two days conference, engineers and scientists decided to choose Mawrth Vallis as second option. It is located in the Oxia Palus valley (22.3°N, 343.5°E) placed 2000 m below datum. Still it is 1000 m less comparing to Oxia Planum with elevation at 3000 m below datum.
Final choice of the landing zone will be performed one year before launch planned for 2020. Landing of the ExoMars lander is planned for 2021.