Once a symbol of Russia's out-of-this-world ambitions, an unmanned probe that was stuck in cosmic purgatory has come crashing back down to Earth.

Phobos-Ground plummeted into the Pacific Ocean late Sunday afternoon, according to Russia's Defence Ministry.

Russia's Air and Space Defence Forces said the ill-fated probe showered debris over part of the southern Pacific, off the Chilean coast about 1,250 kilometres west of Wellington Island.

Spokesperson Col. Alexei Zolotukhin said Russia guides its space debris to that part of open ocean, including space cargo ships that deliver supplies to the International Space Station.

However, the news agency RIA Novosti reported that fragments from the 13,500 kilo probe landed on a much broader swath of land.

The news agency cited ballistic experts, who identified the midpoint of the crash zone in the Brazilian state of Goias.

The probe was designed to travel to a moon of Mars but those plans were derailed when it got stuck in Earth's orbit last November.

Experts struggled to identify the probe's estimated landing point, with guesses stretching from Southeast Asia to South America.

"The earth is filled with water so roughly you have three chances out of four that it will fall on water," Michel Doyon, a space debris expert at the Canadian Space Agency, told CTV News.

Canada, the United States and a large swath of Russia, the probe's birthplace, were outside of the anticipated landing zone.

Kevin Shortt, President of the Canadian Space Society, said the probe wasn't designed to return to Earth this way, which is why the landing point had been difficult to pinpoint.

He told CTV News Channel on Sunday the uncertainty stemmed from the fact the probe returned to Earth "in an uncontrolled manner."

Russia spent $170 million on Phobos-Ground, making it the nation's most expensive and ambitious space project since the Soviet era.

The probe also marked the first time Russia had set its sights beyond Earth's orbit since a failed 1996 mission to Mars.

The probe was to land on Phobos, one of Mars's twin moons, where it was to collect soil samples. It was not supposed to return to Earth until 2014.

Roscosmos, Russia's space agency, has acknowledged the mission required greater preparation for it to be successful.

The agency also said there was little risk of contamination from toxic rocket fuel because much of it would have burned in the atmosphere as the probe plummeted to Earth.

The agency said that only between 20 and 30 fragments, weighing a total of about 200 kilograms, likely survived re-entry.

Indeed, the space era has seen far larger spacecraft crash. NASA's Skylab space station that crashed in 1979 weighed 77 metric tons and Russia's Mir space station that de-orbited in 2001 weighed about 130 metric tons.

Still Russia, once at the front of the pack in the race for space, is red-faced over the massive failure of the probe.

"This mission would have put them on the world stage," Randy Atwood, a senior editor at spaceref.ca, told CTV. "It failed miserably and the word in Russia is heads will roll over this one."

With reporting by CTV's Joy Malbon and files from The Associated Press