The Phobos-Grunt satellite has been circling the planet out of control after a rocket malfunction during the Nov. 8 launch.
It was supposed to travel to Phobos, a Martian moon, to collect soil samples and return them to Earth. (Grunt is Russian for ground or soil).
Roscosmos, the Russian space agency, now predicts the 15-ton car-sized satellite will re-enter the atmosphere on Sunday — possibly landing in the South Atlantic.
But the orbiting satellite could come down anywhere over the Earth between 51 degrees north latitude and 51 degrees south latitude.
That represents an area stretching as far north as Calgary and as far south as the tip of South America.
A space-debris expert at the Canadian Space Agency says the exact re-entry path of Phobos-Grunt will only be known during the satellite's dying hours.
"It's orbiting all over the Earth and given the inclination of its orbit, it's crossing a lot of places where a lot of humans live," the CSA's Michel Doyon said in an interview.
"But where it will end up, no one will be able to tell until only a few hours before."
Doyon sits on the Inter-Agency Space Debris Co-ordination Committee (IADC), which is currently being chaired by Canada. It represents 12 space agencies around the world.
He says the satellite is "about the size of a Honda Civic."
But Doyon stresses the chances of anyone on the ground being hit by debris from the Russian satellite are slim.
"The Earth is covered 80 per cent with water, so you have three chances out of four that it will come down in water," Doyon said.
The satellite had enough fuel on board for its eight-month voyage to Mars and Doyon says most of the toxic fuel will burn up on re-entry.
But some heat-proof debris from the space probe may make it to the ground.
"They expect 20 to 30 fragments will survive re-entry with an overall mass of less than 200 kilograms," Doyon added.
The federal Public Safety Department is also closely watching the doomed satellite through its government operations centre.
It's been reported that the head of Roscosmos has suggested sabotage may have caused the Phobos-Grunt to fail.
"I do not want to blame anyone, but these days there are very powerful means to influence space vehicles," Vladimir Popovkin told Izvestia, a Russian newspaper.
There have been reports the probe may have been "influenced" by powerful American radar in Alaska when it passed over the region.
But Doyon isn't convinced that's what happened to the multimillion-dollar Phobos-Grunt satellite.
"It would appear to be very, very difficult (and) I have trouble believing that," he said.
"I would doubt that there was any active action against a space asset."
Popovkin also admitted the Mars project may have been doomed from the start.
"The probe has been created for a very long time and expiration dates for some of the parts had been nearing," he said.
"If we had not sent it to Mars in 2011, we would have had to throw it away."
Phobos-Grunt joins two other large spacecraft that have landed on Earth in recent months.
All indications are that the remains of NASA's UARS research satellite and Germany's ROSAT space telescope ended up in watery ocean graves.