Russia's Mars moon prober, the unmanned Phobos-Grunt, is expected to fall in the Indian Ocean north of Madagascar between Jan. 14 and 16, according to the Russian space agency Roscosmos.

Roscosmos also forecast that 20 to 30 fragments of the falling spacecraft with a combined weight of 200 kilograms will survive the re-entry. The surviving pieces are expected to scatter in an area between 51.4°N and 51.4°S, it said.

The unmanned spacecraft weighs a total 13.2 metric tons and is larger than the two defunct satellites that recently fell to Earth. It was launched on Nov. 9, but got stranded in orbit when its rocket failed for unknown reasons and it could not be propelled to Mars.

The spacecraft is still loaded with 11 metric tons of highly toxic rocket fuel, but the Russian space agency has assured that this will burn in the atmosphere and pose no danger to the environment and humans. Engineers from the Moscow-based company NPO Lavochkin, which built the spacecraft, say the fuel tank is made of aluminum alloy that easily melts on re-entry, thus burning the fuel up.

Some experts were disputing this, saying it is possible the fuel may have frozen in space and some of it may not burn on re-entry and even rain on populated areas.

Roscosmos also admitted that there is a tiny quantity of the radioactive metal cobalt-57 in one of the instruments in Phobos-Grunt but this poses no threat of radioactive contamination.

The Phobos-Grunt will be the third satellite to crash on Earth in the past five months. In September last year, NASA's defunct Upper Atmosphere Research Satellite, weighing six tons, fell over the Pacific Ocean off the U.S. West Coast. The satellite was 20 years old. The following month, the defunct, minivan-sized ROSAT satellite of Germany fell in the Indian Ocean between India and Indonesia.

The Phobos-Grunt is the latest failure of Russia to send probers to Mars to study its moon Phobos. The $170-million mission was supposed to take soil samples from the Martian moon and then return to Earth in August 2014.

In 1996, the robot Mars 96 also built by NPO Lavochkin crashed shortly after it was launched due to engine failure. Fragments of the spacecraft reportedly fell in the Andes Mountains of Bolivia and Chile, though Russia insisted that the parts fell in the Pacific Ocean. Some 200 grams of plutonium onboard Mars 96 remain missing.

In 1988, under the Soviet Union, Phobos 1 was launched. A software malfunction disabled its solar array and its batteries could not be charged anymore disabling the entire spacecraft.

The following year, Phobos 2 was launched. It was about to approach the Phobos surface to release two landers when contact was lost.