The unmanned Phobos-Ground probe was to head to the Mars moon of Phobos on a 2 1/2-year mission to take soil samples and fly them back to Earth. But the probe became stuck in Earth orbit after its Nov. 9 launch and attempts to send commands that could propel it toward the Mars moon have been unsuccessful.
ESA said that although the agency has halted efforts to contact the probe, it will resume if any changes are reported by the Russian space agency.
A spokesman for the Paris-based ESA said Russia was going to continue to try to contract the probe over the weekend.
Russian deputy space chief Vitaly Davydov said last month that if the spacecraft is not sent to Mars, it could fall to Earth sometime between late December and late February.
The failed spacecraft is 14.6 tons; most of that weight, about 12 tons, is highly toxic fuel.
Experts say that if the fuel has frozen, some could survive the plummet to Earth, but that if it is liquid it will likely combust from the heat of re-entering the atmosphere.
The mission was planned to reach Mars orbit next September and land on Phobos in February 2013.
Scientists hoped that studies of the Phobos soil would help solve the mystery of its origin and shed more light on the genesis of the solar system. Some believe that the crater-dented moon is an asteroid captured by Mars' gravity, while others think it's a piece of debris resulting from Mars' collision with another celestial object.
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