Europe ends calls to stranded Mars probe
It is looking increasingly grim for Russia's Mars mission Phobos-Grunt, which has been stuck circling the Earth since its launch in early November.
Apart from some brief radio contact with the wayward probe just over a week ago, there has been total silence from the spacecraft.
The European Space Agency announced on Friday that it was now ceasing any further attempts to get a signal.
Russian engineers though are expected to keep trying to the last.
"We will stay available for our Russian colleagues in case there is any sign or glimpse of hope from their side," said Dr Manfred Warhaut from Esa's European Space Operations Centre (Esoc) in Darmstadt, Germany.
It was Esa's 15m antenna in Perth, Australia, that first managed to get a response from Phobos-Grunt on 22 and 23 November (GMT). That success was quickly followed by Russian ground controllers using a 0.5m dish in Baikonur, Kazakhstan.
But since then, the probe has not reacted to any commands.
Phobos-Grunt is currently moving in an orbit with an altitude that varies between 200km (perigee) and 340km (apogee).
This orbit is slowly decaying. If engineers cannot re-establish contact and control, the 13-tonne spacecraft will eventually fall back to Earth.
The game-plan of late has been to try to stabilise the orbit by getting commands into the probe that would activate its thrusters and raise it higher in the sky. Getting Phobos-Grunt into a safe "parking orbit" would buy engineers more time to consider their options.
The opportunity to go to Mars, however, has been lost. The changing alignment of the planets now makes the distance to Mars too big to cross.
Phobos-Grunt was built to land on the larger of Mars' two moons, Phobos, and scoop up rock to bring back to Earth.
Such a venture should yield fascinating new insights into the origin of the 27km-wide object and the planet it circles.
The mission is also notable because China's first Mars satellite, Yinghuo-1, has been launched piggy-back on the main Russian spacecraft.
While Esa was always going to provide ground support to the Phobos-Grunt mission, the agency said it now felt it had done everything it could do to help.
"We have exhausted all the technical options at this point," said Wolfgang Hell, Esa's Phobos-Grunt service manager.