MOSCOW (AP) ? A failed Russian probe designed to travel to a moon of Mars but stuck in Earth orbit will come crashing down within hours, the Russian space agency said Sunday.
Roscosmos said the unmanned Phobos-Ground will crash between 1641 and 2105 GMT (11:41 a.m. and 4:05 p.m. EST). It could crash anywhere along the route of its next few orbits, which would include Europe, southeast Asia, Australia and South America. The U.S., Canada and much of Russia are outside the risk zone.
A large part of each orbit is over water, and scientists have estimated that the risks of the probe crashing into any populated areas are minimal. Thousands of pieces of derelict space vehicles orbit Earth, occasionally posing danger to astronauts and satellites in orbit, but as far as is known, no one has ever been hurt by falling space debris.
At 13.5 metric tons (14.9 tons), the Phobos-Ground is one of the heaviest pieces of space junk ever to fall on Earth, and one of the most toxic too. The bulk of its weight is a load of 11 metric tons (12 tons) of highly toxic rocket fuel intended for the long journey to the Martian moon of Phobos. It has been left unused as the probe got stuck in orbit around Earth shortly after its Nov. 9 launch.
Roscosmos predicts that only between 20 and 30 fragments of the Phobos probe with a total weight of up to 200 kilograms (440 pounds) will survive the re-entry and plummet to Earth. It said all of the fuel will burn up entirely in the atmosphere.
The probe's fuel tanks are made of aluminum alloy and should melt early on re-entry, backing up the official assurances. If the fuel indeed burns on re-entry, the probe's dry weight of 2.5 metric tons (2.75 tons) puts it firmly in the league of the ordinary.
By comparison, NASA's Skylab space station that went down in 1979 weighed 77 metric tons (85 tons) and Russia's Mir space station that deorbited in 2001 weighed about 130 metric tons (143 tons). Their descent fueled fears around the world, but the wreckage of both fell far away from populated areas.
The $170-million Phobos-Ground was Russia's most expensive and the most ambitious space mission since Soviet times. The spacecraft was intended to land on the crater-dented, potato-shaped Martian moon, collect soil samples and fly them back to Earth, giving scientists precious materials that could shed more light on the genesis of the solar system.
Russia's space chief has acknowledged the Phobos-Ground mission was ill-prepared, but said that Roscosmos had to give it the go-ahead so as not to miss the limited Earth-to-Mars launch window.
Its predecessor, Mars-96, which was built by the same Moscow-based NPO Lavochkin company, also suffered an engine failure and crashed shortly after its launch in 1996. Its crash drew strong international fears because of some 200 grams of plutonium onboard. The craft eventually showered its fragments over the Chile-Bolivia border in the Andes Mountains, and the pieces were never recovered.
The worst ever radiation spill from a derelict space vehicle came in January 1978 when the nuclear-powered Cosmos 954 satellite crashed over northwestern Canada. The Soviets claimed the craft completely burned up on re-entry, but a massive recovery effort by Canadian authorities recovered a dozen fragments, most of which were radioactive.
The Phobos-Ground also contains a tiny quantity of the radioactive metal Cobalt-57 in one of its instruments, but Roscosmos said it poses no threat of radioactive contamination.
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