Mars has become both a literal and figurative graveyard for robotic missions: in total, 26 have either failed to reach the Red Planet or did not survive touchdown. Those disappointments have hardly discouraged further attempts, however. So who's next in line? The European Space Agency, which, in partnership with Russia's Roscosmos state corporation, will launch a hugely ambitious mission to Mars this month.

If all goes well, the ExoMars program will encompass two separate journeys. This year's orbiter and landing module, which are set to launch together onboard a Russian Proton rocket from the Baikonur Cosmodrome in Kazakhstan, will serve as interplanetary scouts for the second component: a rover mission in 2018.

To prepare for the rover, the orbiter-module duo will have to complete a long list of objectives. For example, the module will test key landing technologies, such as an onboard computer, radar altimeter and parachute. Meanwhile the orbiter, the largest spacecraft ever sent to Mars, will circle the planet at an altitude of 400 kilometers and sniff for traces of methane and other gases that could signpost past or present life below. It will also scan for water ice hidden under the planet's surface and, just as important, help to transmit data between Earth and the rover when it arrives.

All in all, the ExoMars rover has the potential to hit a “home run” in gathering evidence about whether Mars has ever supported life, says Peter Willis, an investigation scientist for NASA's Mars 2020 mission. The ESA rover will have the capability to drill a record two meters deep and carry the most sensitive instruments yet for detecting biological signatures in the samples it pulls, explains Jorge Vago, a project scientist for ExoMars. “If life ever existed on Mars,” he says, “the ExoMars rover will be the first mission that has a real chance of detecting the biological remnants of it.”