Seven months after its launch, a multibillion-dollar project to look for traces of life on Mars faced a crucial moment Wednesday as a test lander hurtled in the direction of the Red Planet.
The future of ExoMars, a joint mission by the European Space Agency and Russia's Roscosmos to look for signs of life on Mars, depends on the successful landing of the Schiaparelli probe as well as the accompanying spacecraft's entry into the planet's orbit.
The automated landing manoeuvre started 121 kilometres above the surface with rapid braking from a speed of 21,000 kilometres an hour. Mission Control at Darmstadt in Germany will be unable to intervene given the time delay of some 10 minutes.
The landing was expected at 1448 GMT, but scientists may not be able to confirm it for some hours.
The ExoMars team reported "good news" shortly before Schiaperelli was expected to enter the planet's atmosphere, retweeting a note from ESA Operations that the probe was "coming through 'strong and clear' as it falls gently towards Mars."
If all goes well, the batteries will provide power for a few days for data to be sent back to Earth from the Meridiani Planum in the Martian highlands.
Schiaparelli has a sort of webcam on its underside that will shoot 15 black-and-white photographs of the Martian surface at intervals of 1.5 seconds, starting at 3 kilometres up.
The probe left Earth from Russia's Baikonur Cosmodrome in Kazakhstan in March together with the Trace Gas Orbiter (TGO), from which it separated on Sunday.
That spacecraft was set to enter Mars' orbit on Wednesday with an approximately 134-minute-long main engine burn set that began at around 1304 GMT, the precision of which is crucial.
Once in orbit, the TGO is set to begin its analysis of the Martian atmosphere at the end of 2017 and will serve as a communications relay for the rover which ExoMars plans to send to Earth's neighbour in 2020.
Scientists faced a nail-biting wait for data, with ESA under pressure to deliver results after its previous project to land a spacecraft on Mars failed when the British-built Beagle 2 was declared lost on Christmas Day 2003, only to be found 11 years later by NASA's Mars Reconnaissance Orbiter.