The European Space Agency (ESA) has chosen its primary site for its first Mars rover, which is scheduled to land on the red planet in 2019. The site, Oxia Planum, lies a few hundred kilometers southwest of Mawrth Vallis and east of the Chryse Planitia lowlands. The attraction is the numerous signs that water once flowed there, bringing with it the possibility of life, either today or far in the past.
ExoMars is a collaborative program between ESA and its Russian counterpart, Roscosmos. The first launch in 2016 will include the ExoMars Trace Gas Orbiter (TGO) plus a stationary lander, called Schiaparelli, whose primary purpose is to test entry, descent, and landing technology. The TGO will survey the martian atmosphere for traces of methane and other gases at concentrations less than 1%. These gases could be signs of biological activity, and the results may influence the final choice of landing site for the rover.
The second launch, lifting off in 2018, will carry the ExoMars rover on its 9-month journey. The landing will be achieved by aerobraking, parachutes, and thrusters. The landing capsule will become an environmental monitoring station whereas the rover will search for signs of past or present life on Mars. A drill on the rover is capable of penetrating 2 meters below the surface and also features an infrared spectrometer to study rocks in the borehole and extract samples for the rover's analytical laboratory.
Mars's surface area of about 145 million square kilometers is comparable to the land area of Earth. In choosing the best landing site, researchers have been looking for somewhere that is geologically diverse but at least 3.6 billion years old. That's because scientists believe liquid water on the surface may have been more prevalent in the early millennia of Mars's evolution. The site also has to be free of steep slopes, large rocks, or cliffs.
The agency received eight proposals in response to a December 2013 call for suggestions, and the Landing Site Selection Working Group chose four in October 2014. The four candidates—Mawrth Vallis, Oxia Planum, Hypanis Vallis, and Aram Dorsum—are all relatively close together and all close to the martian equator.
The landing site at Oxia Planum is home to deep sinuous valleys, hundreds of kilometers long. The eastern part of the site includes the relic of a fan-shaped deposit, 15 kilometers wide and 21 kilometers long. This flat feature may be the remains of an ancient delta or an alluvial fan.









