Russian space Agency Roscosmos has predicted that the unmanned Phobos-Ground probe will fall out of Earth's orbit and land in the Indian Ocean near Madagascar on either Sunday or Monday.
The precise timing of the fall to Earth can only be determined later but Roscosmos has said that unless someone spots fiery streaks in the sky, no-one may know where it ends up.
The return comes just two and a half months after the Phobos-Grunt probe launched, before a technical glitch left it stranded in orbit around Earth instead of bound for Mars to collect soil samples.
The experts say that the probe, which weighed 14.6 tons, is one of the largest spacecraft ever to plummet to Earth but is unlikely to pose a risk to people on the ground
It is potentially the most toxic to fall to Earth though, with it containing around 12 tons of highly toxic rocket fuel which would have been used for the journey to Phobos. Read More